APPARATUS FOR MEASURING THE PRESENCE OF A WEAK ACID OR A WEEK BASE IN A LIQUID

APPAREIL DE TITRAGE DES ACIDES OU BASES FAIBLES EN SOLUTION

English Abstract

APPARATUS FOR MEASURING THE PRESENCE OF A
WEAK ACID OR A WEAK BASE IN A LIQUID
ABSTRACT OF THE DISCLOSURE
A method and apparatus for measuring the presence
of a weak acid or weak base in a liquid by withdrawing a
sample from the liquid; reacting the sample with an excess
amount of strong acid or strong base reagent; measuring the
conductivity of the reagent-treated sample and comparing the
measured conductivity to a standard value.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. Apparatus for measuring the acidity or alkalinity
of water comprising:
(a) a flow line for a sample of the water to be
measured;
(b) means to control the rate of flow of said
water sample through said line;
(c) a first conductivity cell on said line
adapted to measure the electrical conductivity of a water
sample flowing through said line;
(d) a first fluid inlet downstream from said
first conductivity cell on said line for adding a controlled
proportion of reagent to a water sample flowing through said
line;
(e) a second conductivity cell downstream from
said first fluid inlet for measuring the electrical
conductivity of a water sample flowing through said line
after the addition of a controlled proportion of reagent;
(f) a second fluid inlet downstream from said
second conductivity cell on said line for adding a controlled
proportion of a liquid to a water sample flowing through said
line;
(g) a third conductivity cell downstream from
said second fluid inlet on said line for measuring the
electrical conductivity of a water sample flowing through
said line after the addition of a controlled proportion of
liquid; and
(h) an electronic calculator connected to said
first, second and third conductivity cells and adapted to
generate an output signal indicative of the acidity or
alkalinity of a water sample flowing through said line.
36

2. An apparatus as recited in claim 1 further
comprising means for controlling the level of dissolved
carbon dioxide in a water sample flowing through said line.
3. Apparatus as recited in claim 2 wherein said
means to control the level of dissolved carbon dioxide
comprises a carbonating apparatus adapted to adjust the
pH of a water sample flowing through said line to a pH from
about 5 to 8.
4. Apparatus as recited in claim 3 wherein said
carbonating apparatus is adapted to adjust the pH of a water
sample flowing through said line to a pH from about 7 to 8.
5. An apparatus as recited in claim 1 further
comprising means between said first fluid inlet and said
second conductivity cell on said line for uniformly mixing
reagent added through said first fluid inlet with a
sample flowing through said line.
6. An apparatus as recited in claim 1 further
reciting means located between said second fluid inlet and
said third conductivity cell on said line for uniformly
mixing liquid added through said second fluid inlet with a
water sample flowing through said line.
7. Apparatus as recited in claim 1 further comprising
a reagent constant head device having a supply chamber, a
return chamber adapted to receive excess reagent overflowing
from said supply chamber, a supply line from said supply
chamber to said first fluid inlet, a reagent reservoir, a
fill line from said reagent reservoir to said supply chamber,
pump means on said fill line for transferring reagent from said
37

reagent reservoir to said supply chamber and a return line
from said return chamber to said reagent reservoir.
8. Apparatus as recited in claim 1 wherein said
electronic calculator comprises an analog computer adapted
to solve the equation:
<IMG>
where Eo is the initial conductivity of the water sample,
E2 is the conductivity of sample after addition of reagent
through the first fluid inlet, E3 is the conductivity of the
water sample after the addition of liquid through the second
fluid inlet, X is the solution alkalinity, X2 is the concen-
tration of reagent after the addition of reagent through the
first fluid inlet, X3 is the concentration of reagent after
the addition of liquid through the second fluid inlet, and
Mi is the initial rate of change of conductivity of the
original sample upon the addition of reagent.
9. Apparatus as recited in claim 8 wherein said
analog computer further comprises means to adjust the
computer to varying rates of change of conductivity due to
the presence of different species in the original sample.
10. Apparatus as recited in claim 1 wherein said
means to control the rate of flow of a water sample through
said line comprises a flowmeter and a valve on said line.
11. Apparatus as recited in claim 1 further comprising
a bypass line connected to said flow line upstream from said
first conductivity cell and to said second fluid inlet, and
means on said bypass line for regulating the flow of water
sample therethrough.
38

12. Apparatus as recited in claim 7 further comprising
a connecting line connecting said reagent supply line and
said second fluid inlet, and valve means on said connecting
line for regulating the flow of reagent therethrough.
13. Apparatus as recited in claim 1 further comprising
first, second and third conductivity meters connected to said
first, second and third conductivity cells respectively, and
a multiple chart recorder connected to said first, second
and third conductivity meters and to said electronic
calculator.
14. Apparatus as recited in claim 1 wherein said first.
fluid inlet, said second conductivity cell, said second fluid inlet
and said third conductivity cell are all disposed on a
vertically oriented segment of said flow line and a gas vent
is provided at the top of said vertical line segment.
39

Description

987
The use of conductivity measurements to determine
the composition of liquids is known, as exemplified by
United States Patent No. 2,823,673, Thurston E. Larson et
al, issued April 29, 1958. More recently, me*hods have
been proposed for analyzing the composition of solutions
utilizing differential electrical conductivity. Such methods
are exemplified by United States Patent No.~ 3,531,252,
~Iubert M. Rivers, issued September 29, 1970. Conductivity
techniques are highly accurate and conductivity apparatus
10 generally requires only minimal maintenance. However, no
conductivity method or apparatus has been available which
would satisfactorily measure the presence of a weak acid
or weak base in a liquid~
Generally, a substantial portion of a weak acid
or weak base in solution is present in un-ionized form.
Since the conductivity of a liquid is a function of the
ions therein, conventional conductivity methods are unsuited
for measuring the amount of un-ionized weak acid or base
present in a liquid. Further, although conductivity measure-
20 ments are generally highly sensitive, quantitative detectionof minute quantities of ions resulting from the limited
ionization of a weak acid or base in solution is still very
difficult.
The alkalinity of water is an important factor in
determining whether it will be scale forming or corrosive.
In many situations, control of the acidity or alkalinity of
a liquid is extremely critical, such as in steam boilers or
turbines where deviation from ~a preferred alkalinity has a
corrosive effect on expensive equipment. Thus, the aIkalinity
30 of water is an important water property which often requires
continuous monitoring to ensure suitability for certain
industrial water uses. The determination of alkalinity has
heretofore been a laboratory procedure not adaptable for
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10429~7
continuous on-site monitoring. In most water supplies, the
ma]ority of the total alkalinity results from the presence of
HPO4 , HCO3 , CO3 and NH3. Due to the low conductivities
of such species, direct conductivity measurements of their
presence are not practicable.
Also a buffer may be added to the water to resist
; changes in acidity or alkalinity. A buffer generally
consists of two ingredients; a weak acid and a weak base
although it is well known that a solution containing only a
weak acid or only a weak base may act as buffered solution.
When a strong acid is added to a buffered liquid the weak
base reacts with the strong acid to produce weaker acid, and
less of an increase in acidity of the liquid results than
would be produced by the addition of the same amount of strong
acid to an unbuffered liquid. Similarly, when a strong
base is added to a buffered liquid the weak acid of the buffer
reacts with the strong base to produce a weaker base and less
of a change in alkalinity of the liquid results than would
be produced by the addition of the same amount of strong
base to an unbuffered liquid. The capacity of a buffered
liquid to resist changes in acidity or alkalinity depends
on the absolute amount of the appropriate buffer ingredient,
i.e. weak acid or weak base, present in the liquid. Only
; minimum amounts of buffer are used since large concentrations
are undesirable. Consequently the buffer capacity often must
be carefully monitored to make certain the buffer ingredients
are not exhausted thereby allowing the acidit~ or alkalinity
of the liquid to deviate from the critical range. This
requires the ability to accurately measure the presence of
small amounts of weak acid or weak base in the liquid.
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104Z9~7
In accordance with one aspect of this invention,
there is provided an improved apparatus for quantitatively
; determining the presence of a weak acid or a weak base in
a liquid.
In accordance with another aspect of this
invention, there is provided an apparatus for measuring
the presence of a weakly acidic or basic chemical in a
liquid which utilizes the high mobility of hydronium or
hydroxide ions to achieve increased sensitivity.
; 10 In accordance with another aspect of this
invention, there is provided an apparatus for determining the
alkalinity of a water supply which is not subject to CO2
interference like conventional colorimetric and potentiometric
procedures.
In accordance with another aspect of this
; invention, there is provided an apparatus for continuous
on-site monitoring of the al]calinity of a water supply which
is highly accurate and which requires minimal maintenance.
In accordance with another aspect of this
invention, ~here is provided an apparatus for continuously
measuring the alkalinity of a water sample which prevents the
accumulation of entrained gases which otherwise would cause
irregular sample flow.
In accordance with another aspect of this
invention, there is provided an apparatus for continuous
measurement of the alkalinity of a water supply which can
generate an electrical output signal directly proportional
to the sample alkalinity.
In accordance with another aspect of this
invention, there is provided an apparatus for measuring the
total alkalinity or acidity of a water supply due to the
.

~04Z987
presence of small amounts of weak bases or weak acids which
will reduce interference from the background conductivity
of neutral salts in the water.
In accordance with this invention, there is
provided apparatus for measuring the acidity or al~alinity
` of water comprising:
` (a) a flow line for a sample of the water to be
measured;
- (b) means to control the rate of flow of said
water sample through said line;
(c) a first conductivity cell on said line
adapted to measure the electrical conductivity of a water.
sample flowing through said line;
(d) a first fluid inlet downstream from said first
conductivity cell on said line for adding a controlled pro-
portion of reagent to a water sample flowing through said
line;
(e~ a second conductivity cell downstream from
said first fluid inlet for measuring the electrical conductivity
of a water sample flowing through said line after the addition
of a controlled proportion of reagent;
(f) a second fluid inlet downstream from said
second conductivity cell on said line for adding a controlled
proportion of a liquid to a water sample flowing through said
line;
(g) a third conductivity cell downstream from
said second fluid inlet on said line for measuring the
electrical conductity of a water sample flowing through said
line after the addition of a controlled proportion of liquid;
and
(h) an electronic calculator connected to said
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~(~4;~7
first, second and third conductivity cells and adapted to
~enerate an output signal indicative of the acidity or
alkalinity of a water sample flowing through said line.
Previous apparatus for determining the composition
of liquids have measured the conductivity of the ionic
components of the liquids directly. As mentioned hereinabove,
the total alkalinity o~ a water results from the presence of
weakly basic species which cannot be quantitatively measured
by conventional conductivity techniques, and buffers generally
include a substantial portion of un-ionized wea} acid or base
species which cannot be detected by conventional conductivity
measurements. Further, the ionized weak acid or base
constituents are often large and complex ions which have low
mobility in solution or which may form complexes with other
ions and consequently have a correspondingly low c~nductivity.
For these reasons, direct conductivity measurements of
liquids are inade~uate for measurement of buffer capacities
or ~or determining the alkalinity of a water supply.
The invention obviates the above-mentioned problems
by providing apparatus for completely reacting the weak acid
or base with a reagent selected from the group consisting of
relatively strong acids and relatively strong bases.
Preferably the acid reagents used in the apparatus of the
invention are those which are essentially 100% dissociated
in solution such as sulfuric acid, hydrochloric acid and
nitric acid, but other relatively strong acids such as
phosphoric acid, sulfurous acid, dichloracetic acid, maleic
acid, naphthalenesulfonic acid, picric acid, oxalic acid,
and trichloroacetic acid may also be utilized. The same is
true of the base reagents used in the apparatus of the inven-
tion. Alkali meta~ hydroxides are preferred, but other
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~ ~1)4~29t~7
relatively strong bases such as acetamide, p~razine, and
urea may be used. Generally, an acid or base having a
dissociation constant greater than about 10 under the
prevailing conditions may be suitably utilized in the
invention. The term "relatively strong acid or base reagent"
as used herein is intended to refer to all such acids and
bases. The strong acid or base reagent is added in excess of
the amount necessary to completely react with all of the weak
acid or base in the liquid, and the conductivity of the
resulting solution is measured. An acid reagent is added to
the liquid when it is desired to measure the presence of
weak base, e.g. the alkalinity of a water or the capacity of
a buffer to resist acid, and a base reagent is added to the
liquid when it is desired to determine the quantity of weak
acid present, e.g. the acidity of a water or the capacity of
a buffer to resist basic influences. In this sense a weak
base refers to a co~bination of a strong cation and a weak
anion such as NaHC03, and a weak acid refers to a combination
of a weak cation and a strong anion such as NH4Cl.
The apparatus of the invention performs the step
of comparing the measured conductivity of a solution contain-
ing a weak acid or weak base after the addition of a known
amount of a relatively strong acid or strong base with a
standard value. The standard value may usually be conveniently
obtained by measuring the conductivity of a similar solution
containing no weak acid or base also treated with the same
known amount of strong acid or base reagent. Alternatively,
the standard may be calculated according to theoretical
principles from the characteristics of the conductivity cell
and the concentration, charge and mobility factor o the ions
in solution. A useful standard value for comparlson may
-- 7 ~
.;

~4298~
also be derived by extrapolation from the initial conductivity
of the water sample prior to the addition of any reagent and
the initial rate of change of conductivity upon the addition
of reagent.
; The difference in the conductivity, i.e.
conductivity differential, is a direct fun~tion of th~ amount
of weak acid or base present in the sample and provides a
method of increased sensitivity for this determination.
Since some of the hydrogen ions or hydroxide ions added with
the aforementioned reagents to the solution containing weak
acid or base will be oonsumed by neutralization reaction with the weak
( acid or base, the remaining concentration and consequently,
the conductivity of the solution after addition of the strong
acid or base reagent will be less than the conductivity of the
solution also treated with reagent but with no weak acid or ;
base present. While direct conductivity measurements are
incapable o accurately detecting un-ionized components in
a solution, this apparatus accuxately indicates the quantita-
tive presence of all such components which react with a
( 20 strong acid or strong base.
The electrical conductivity of a liquid is
dependent not only on the concentration of the ions in
solution but also on the mobility of the ions and increases
with increasing ion mobility. Since hydrogen ions and
hydroxide ions have the highest mobilities of any ionic
substances in an aqueous solution, they also have the highest
conductivities of any ion at a given concentration. For
example, .01 molar solution of hydrochloric acid will have
a greater conductivity than a .01 molar solution of sodium
chloride because hydrogen ions have a higher con`ductivity
than sodium ions. Accordingly, when all other factors are
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~1~)4Z987
equal, such as applied voltage and distance between
electrodes, a lower concentration of hydrogen ions will
conduct ~he same current as a significantly higher concen-
tration of sodium ions. Thus, for a given apparatus having
; a fixed maximum sensitivity to current, much smaller
differences ln the concentration of hydrogen ions may be
detected than of any other cation, and much smaller differences
in the concentration of hydroxide ions may be detected than
of any other anion. Application of this principle in the
apparatus of the invention results in the ability to measure
the presence of a weak acid or base with extreme sensitivity.
The mobility of ions in solution, and consequently
their conductivity, varies with changes in temperatureO
Generally, an increase in temperature will increase the
mobility of the ions, and thus the conductivity of a given
liquid will increase as its temperature is raised. ~ccording- !
ly, it may be desirable to control the temperature of a
liquid sample when making conductivity measurements to
determine the concentration of various components in the
liquid. In some of the embodiments of the apparatus of the
invention di~closed in this specification, the temperature
of a liquid sample being tested is maintained at its boiling
temperature. If, however, the rate of flow of sample through
the apparatus of the invention is sufficiently high that
only minimal changes in sample temperature are encountered,
then no special measures need be undertaken to control the
sample temperature.
The conductivity may he recorded on any suitahle
recording means, such as a conventional strip chart recorder,
and subsequently analyzed by comparison with a table of
conductivity differences versus known wea}; acid or base
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~04Z98~
concentrations. Alternately, in a buffered liquid the
conductivity difference may be utilized directly to control
the addition of additional buffer to the liquid.
Under some circumstances, sensitivity or accuracy
of the measurements is enhanced by degassing the solution,
for example to remove dissolved C02. This may be effected
by boiling or by sparging the solution or by other methods.
If C02 is not removed, interference with the measurement of
the presence of a weak base in the solution may be prevented
by adding sufficient acid reagent to suppress the ionization
of the carbonic acid formed by the C02 in solution.
The apparatus of the invention is not limited to
use in a~ueous systems; it is effective in an analogous
manner in other solvents in which electrical conductivity is
a measurable property such as liquid ammonia.
~lso, the apparatus is suitable for continuously
monitoring 10wing liquids. In continuous operations, a
liquid sample is continuously or periodically injected into a
test stream either before or after addition of the reagent
and the conductivity is continuously monitored downstream
from the points where the sample and/or reagent are added.
Furthermore, the inventive apparatus is capable
of measuring the presence of a weak acid or base even though
other ions from neutral salts are present in the sample so
long as the background conductivity due to the presence of
other ions is taken into account in determining the standard
value. One way to achieve this is to base the standard value
on a measurement of the initial conductivity of the sample
prior to the addition of any reagent.
The invention will be more completely explained
hereinafter by reference to an illustrative experiment and by
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9~7
the description of arrangements of apparatus for measuring
the buffer capacity of boiler water used to generate ste~m
for a steam turbine power plant, for monitoring the
borate content in a nuclear reactor in which boron is
employed as a chemi~al shim or neutron absorber, and for
monitoring the alkalinity of a minicipal water supply. It
is understood, however, that the invention is applicable
to any situation whera the presence of a weak acid or base
in a liquid is to be measured.
BRIEF DE5~RIPTION OF THE DRAWINGS
The invention will be described with reference to
the following drawings wherein:
Figure 1 is a schematic representation of a test
apparatus used in an illustrative test to demonstrate the
reliabili.ty and sensitivity of the invention;
Figure 2 is a graph showing the results of the
illustrative test conducted with the apparatus of Figure l;
Figure 3 is a schematic representation of an
apparatus suitable for monitoring the buffer capacity o
boiler water condensate;
Figure 4 is a schematic representation of an
apparatus suitable for measuring the boric acid concentration
in a solution used as a neutron absorber in a nuclear reactor;
Figure 5 is a schematic representation of an
apparatus for measuring the alkalinity of a water supply;
Figure 6 is a schematic circuit diagram of an
electronic calculator adapted for use with the apparatus of
Figure 5;
Figures 7 and 8 are graphs showing the results of
tests conducted with the apparatus of Figure 5.
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3.~425~87
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Test 1
Figure l is a schematic representation of an
experimental arrangement used to illustrate the effectiveness
of the present invention. In the experiment sodium bicar-
bonate served as a weak base and sulfuric acid was used as
the reagent. Initially, a flow of de-ionized water was
established through conduit l. The total flow rate was
maintainted at approximately 310 - 315 ml. per min. and the
temperature of the water was maintained at 20C. The
residual background conductivity of the water was measured
by conductivity cells S and 10 for comparative purposes and
was found to be 0.06 micromhos. Throughout the experiment,
the conductivity measurements from both cells were recorded on
a conventional dual recorder 11 and are shown graphically in
Figure 2 wherein the dotted line represents the conductivity
measurement from cell 5 and the solid line represents the
measurement from cell 10.
`~ The results are also summarized in ~able 1 below:
Table 1
Cell 5 Measurement Cell 10 Measurement
Start 0.06 u mhos 0.06 u mhos
Add H2SO4 G.06 u mhos 1.89 u mhos
Add NaHCO3 0.22 u mhos 1.24 u mhos
Sparger On 0.22 u mhos 1.11 u mhos
Sparger Off 0.22 u mhos 1.24 u mhos
Stop NaHCO3 0.06 u mhos 1.89 u ~hos
Stop H2SO4 0.06 u mhos 0.06 u mhos
After the residual conductivity was measured,
valve 13 was opened to admit a 0.0002N solution of sulfuric
acid from tank 7 through T-connector 6 into the water flowing
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~ 04ZgB7
through line 1 at a controlled dilu~ion rate of approximately
1:50. The resulting solution then passed through chamber 8
to ensure uniform mixing. When the addition of acid was
begun, the conductivity measurement from cell 10 changed
abruptly to 1.89 micromhos while the conductivity measurement
from cell 5 remained at 0.06 micromhos. This provided a
measure of the conductivity resulting from the addition of
the reagent to an unbuffered solution to serve as the standard
value. A controlled amount of sodium bicarbonate soltuion
was then introduced into the water from tank 3 through T-
connector 2 by opening valve 12 so that the resulting
concentration of sodium bicarbonate was about 0.13 parts per
million. The sodium bicarbonate solution then passed through
mixing chamber 4. The change in conductivity measured by
cells 5 and 10 each provide a measure of the amount of sodium
bicarbonate added. Af~er the addition of sodium bicarbonate
I
was commenced, the conductivity measurement from cell 5
increased from 0.06 micromhos to 0~22 micromhos, a change
of 0.16 micromhos. The conductivity measurement from cell
10 dropped from 1.89 micromhos to 1.24 micromhos. A
further slight decrease in the conductivity measurement from
cell 10 from 1.24 micromhos to 1.11 micromhos was effected
by bubbling CO2-free gas through the solution in sparging
chamber 9 to remove dissolved carbon dioxide produced by
the neutralization of the bicarbonate ions. This gave a
total conductivity change of 0.78 micromhos when the
invention was used to measure the sodium bicarbonate content
of the solution as compared to a change of only 0.16
micromhos when the conductivity of the sodium bicarbonate
was measured directly. Significantly, the change in
conductivity caused by the sodium bicarbonate when the acid
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~4;Z915 7
reagent was present was almost five times as great as when
no acid was added. This clearly demonstrates the increased
sensitivity achieved by the invention.
Figure 3 is a schematic xepresentation of an
apparatus or ~uantitatively measuring the presence of the
basic buffer ingredient in a slightly buffered alkaline
water source such as a boiler condensate return line. A
sample of the condensate is withdrawn from return line 21
through valve 22 and passed to a constant head device
designated by the numeral 23. The constant head device
comprises an inner chamber 24 connected to outlet line 25
and an annular outer chamber 26 connected to waste line 27.
The sample feed rate to chamber 24 is slightly greater than
the outflow rate through line 25 so that a small portion of
the sample ovarflows chamber 24 to waste thereby maintaining
a constant head on the main portion of the sample which
flows out through line 25 to heat exchanger 28 where it is
preheated by effluent from the conductivity cell 40'. The
sample then goes to mixing tee 29 where it is mixed with a
controlled proportion of a strong acid reagent brought in
through line 30 from constant reagent head device 31. The
proportion of reagent supplied must be in excess of the
amount required to react with all of the buffer ingredient
in the sample. After mixing with the acid, the sample
solution passes through flowmeter 32 and valve 33 to a stain-
less steel chamber 34. The flowmeter and its associated
valve are used to maintain a constant flow-rate of treated
sample into the chamber. An electrical immersion stain~ess
steel heater 35 in chambex 34 is used to heat the reagent-
treated sample to boiling. Boiling is a convenient manner
of degassing the solution and of maintaining a constant
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temperature. A conventional reboil regulator 36 associated
with heater 35 adjusts the heating of the sample to maintain
a plume of steam from vent 37 in chamber 34. The heatea
sample leaves chamber 34 through line 38, which i5 preferably
vented as at 39 to prevent syphoning of the sample from
chamber 34 thereby maintaining the level in the chamber, and
passes to conductivity cell 40 where the conductivity of
~he treated sample is measuredO The conductivty measurement
is sensed by comparator device 41 which compares the
- measured value to a standard calibrated in a manner described
hereinafter. The difference between the measured and standard
values is recorded on a strip chart recorder 42. After the
conductivity is measured, the sample flows through line 43
to heat exhanger 28 where some of its heat is transferred to
the incoming sample stream before being discharged to
waste at 44.
The standard used in the comparator device 41 may
be calibrated by closing valve 22 to shut off the flow of
sample to the system and opening valve 45 which communicates
with a supply of de-ionized water 46. The de-ionized water
then flows through the system under the same conditions of
flow, tempexature, pressure and reagent application as did
the condenser water. The conductivity of the de-ionized water
plus added reagent is measured as before by conductivity cell
40 and the result of the measurement is again passed to the
comparator. Since the conductivity of the de-ionized water
plus the reagent should approach theoretical values, the
standard in the comparator is adjusted by means of a variable
resistor until the measured value and the standard are
balanced, and zero buffer is indicated on the recorder. After
the calibration is completed, valve 45 is closed and vaIve 22
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~ Z9~7
is reopened to resume monitoring of the buffer cap~city of
the boiler condensate sample stream. The diference between
the conductivity of the reagent-treated boiler condensate
sample and the standard, i.e. the conductivity of the
reagent-treated de~ionized water, indicates the quantity of
buffer in the boiler condensate.
Alternatively, a standard buffer solution may be
used in place of the de-ionized water in the calibration
operation. The difference in conductivities then indicates
the deviation of the boiler condensate buffer content from
the standard instead of the absolute amount of the buffer
in the condensate. If desired in situations where buffer is
continuously added to the boiler feed water supply, the
signal from comparator device 41 may be used to control the
addition or buffer from a buffer supply 47 to the stream
flowing through line 21 by means of a solenoid valve 48
; interposed in connecting line 49.
It is also possible to derive the standard value
from a measurement of the conductivity of the sample prior
to the addition of the reagent. For this purpose a conductiv-
ity cell 40" may be included on line 25 upstream from the
acid reagent source analogous to conductivity cell 5 in
Figure 1.
Figure 3 also shows an optional arrangement which
is useful for confirmatory purposes and provides for
increased accuracy. A second controlled amount of reagent
is added to the stream flowing through line 43 from acid
reagent constant head device 31' through line 30' and
- mixing tee 29'. The conductivity of the sample stream is
again measured by conductivity cell 40' and the result passed
to comparator 41 for comparison with a second standard value.

~()4Z987
It is expressly contemplated that the second standard value
could be equal to the first standard value. The addition of
a second increment of reagent and the second conductivity
measurement are useful to confirm that the reagent supply
system is operating properly and that all of the weakly
acidic or basic chemical in the sample was completely reacted
by the first increment of reagent. The second reagent addition
and measurement also enable determination of the rate of
change of conductivity u~on the addition of excess reagent
which varies depending on the different species present in
the solution thereby making it possible for the apparatus
to compensate for the background conductivity and interference
resulting from the presence of other species such as sulfate
salts in the sample in order to achieve increased accuracy.
Possibl~, there could be a series of three, four or even
more sequential additions of reagent each followed by a
subsequent measurement of the conductivit~. Different
reagents could be added at any of the successive points.
A further apparatus is illustrated schematically
in Figure 4. This arrangement is adapted for situations
where for economic or other reasons only very small amounts
of sample are used. This arrangement also conserves the
amount of reagent required in the measurement operation if
the concentration of weak acid or base in the sample being
measured is quite high. For example, this arrangement is
useful in measuring boric acid used in nuclear power plants
in concentrations on the order of 2500 ppm. Numeral 50
designates a conduit in which a flow of highly pure strong
base reagent is established. The basic reagent may be
provided by diluting a standard reagent solution with de-
ionized or distilled water in mixing tee 51. The reagent
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: 104Z9~7
supply 52 and the high purity water supply 53 may be
provided with constant head devices 54 and 55 respectivély
to ensure uniform dilution of the reagent. Alternatively
a small volume pump may be used to feed the reagent into the
high purity water line at a controlled rate. A mixing
chamber 56 may also be inserted into the line to ensure
uniform mixing. The reagent flow is split into two streams
at 57 which flow through lines 58 and 59. An injection device
60 withdraws a small sample of borate solution from the
~; 10 reactor through line 61 and injects it into line 99. The
; volume of the injected sample must be negligible comparëd to
the volume of reagent flowing through line 59 to avoid
distortion of the results due to dilution. Alternately, an
amount of d~-ibnized water equal to the volume of the sample
could be added to the stream flowing through line 58 to
equalize the dilution. It is of course essential that the
strong base flowing through line 59 be in excess of the
amount required to completely react with all of the boric
acid in the sample injected into the line. The two streams
then flow to conductively cells 62 and 63 where the
conductivity of each is measured. The results of the two
measurements are sensed by comparator device 64 which
compares them and provides a signal to recorder 65 to
indicate the difference in conductivity. The two streams
are then discharged as at 73.
A mixing chamber 66 may be provided on line 59 to
facilitate complete mixing of the sample and reagent. To
ensure the two conductivity measurements are strictly compar- -
able, it is desirable to equalize the flows through lines
58 and 59. For this purpose flowmeters 67 and 68 and control
valves 69 and 70 are inserted in lines 58 and 59 respectively
and a chamber 71 identical to mixing chamber 66 is inserted
- 18 -

in line 58. ~4~9~7
To further conserve on the amount of sample and
reagent utilized, the operation of injection device 60 may
be controlled by a timer 72 to provide for intermittent
injection of a controlled volume of sample into line 59.
The concentration of reagent may be reduced so long as
chamber 66 contains a controlled excess of the reagent each
time a sample is in~ected. The boric acid quickly reacts
with the basic reagent in chamber 66 producing a temporary
decrease in conductivity sensed by conductivity cell 63
i; which shows up as a peak on recorder 65. In either the
direct or intermittent methods of operation, the recorder
may be calibrated to provide a direct readout in concentration-
of boric acid in the sample being measured by inje~ting
standard samples of known concentration through the system.
With a little modification, the apparatus shown
ln Figure 4 can also be utilized to advantage to inject a
controlled excess of reagent into a flowing sample stream
instead of injecting a sample into the reagent stream as
shown in Figure 4. This technique eliminates distortion due
i to background conductivity of the sample.
Figure S illustrates an apparatus for monitoring
the alkalinity of a municipal water supply down to less than
10 ppm expressed as CaCO3. A sample of the water is passed
through a feed line 81 and a spray nozzle 82 into a carbonating
device generally designated by reference numeral 83 comprising
an upper chamber 84 and a lower chamber 85 separated by a
foraminous member 86. A bed of dispersing media, such as
small glass beads 87, is disposed on top of foraminous
member 86, and carbon dioxide from a CO2 source 88 is fed
through a connecting line 89 into the separating media bed.
-- 19 --

:
~L~4Z9~7
The water is carbonated as it gravitates through the media
; bed and the foraminous member into lower chamber 85. An
overflow partition 90 separates the main body of chamber 85
from an overflow line 91 so that when the carbonated water
sample reaches a depth equal to the height of the partition,
the excess will flow over the partition and out the overflow
line so that a constant head of water sample is maintained
in chamber 85. A gas vent 92 prevents the buildup of super-
atmospheric pressures within the carbonator.
Sample water from carbonator 83 passes from lower
chamber 85 through a flow line 93 to a discharge point 94.
It is convenient to cause the sample to flow through line
93 under the influence of gravity by disposing outlet 94
and all parts of line 93 lower than chamber 85. The heights
of chamber 85 and outlet 94 are adjustable relative to each
other so that the sample head may be varied in order to
achieve the desired sample rate of flow through the apparatus.
In the illustrated apparatus, the sample head can be varied
~rom about 3 to about 12 inches of water in order to achieve
a constant flow rate in the range from 250 to 300 ml per
minute. Line 93 includes a vertically oriented segment on
which are mounted successively along the path of flow, a valve ~5,
a flowmeter 96, a first conductivity cell 97, a first fluid
inlet 98, a first mixing chamber 99, a second conductivity
cell 100, a second fluid inlet 101, a third fluid inlet 102,
a second mixing chamber 103, a third conductivity cell 104
and a gas vent 105. Conductivity cells 97, 100 and 104 are
connected respectively to conductivity meters 106, 107 and
108. Suitable conductivity meters are Model R~5 Solumeters
with 100 mv. outputs manufactured by Beckman Instruments,
Inc. The three conductivity meters are in turn connected to
- 20 -

4~:9B7
an electronic analog computer 109 programmed to calculate
the total alkalinity of the water from the three measured
conductivity values. In the preferred embodiment illustrated~
the computing apparatus and the three conductivity meters are
all connected to a multiple chart recorder 110 such as a
~Model VKP potentiometric chaxt recorder manufactured by
Beckman Instruments, Inc. in order to provide a permanent
graphic record of the sample alkalinity. The output of
calculator 109 may also be utilized to control an output
device 111 which may be any of a number of types of apparatus
such as an alarm system, a shut-off mechanism or an apparatus
for automatically adding treatment chemicals.
Fluid inlet 98 is connected to an acid reagent
delivery system via reagent delivery line 112 which leads
from a reagent constant head device 113. Reagent constant
head device 113 comprises an annular supply chamber 114
and a return or overflow chamber 115 separated by a partition
116 which controls the depth of the reagent. As with the
sample constant head device 83, the height of the reagent
constant head device is adjustable with respect to the
height of outlet 94 in order to facilitate adjustment of the
head of reagent in order to oontrol the rate of flcw of reagent
through the apparatus. In the apparatus of Figure 5, the
reagent head may be adjusted up to about 10 inches of water.
Reagent from a reservoir 117 is continuously pumped to
supply chamber 114 through a fill line 118 by means of a pump
119. A filter 120 is interposed in line 118 to assure that
the reagent is free of solid contaminants. Reagent is pumped
to supply chamber 114 at a higher rate than it is withdrawn
through line 112, and the excess flows over the top of
partition 116 into return chamber 115 and is returned to the
- 21 -

~04zgi37
reagent reservoir 117 through a return line 121. It is
; desirable to have the reagent reservoir vented as shown at
122 in order to maintain the reagent supply at atmospheric
pressure and ensure a continuous ready flow of reagent.
Reagent supply line 112 is also connected to
fluid inlet 101 on line 93 by means of a line 123, and a
valve 124 is provided on line 123 in order to enable
regulation of the flow reagent therethrough.
A bypass line 125 running from a fork 126 located
in line 93 upstream of valve 95 to fluid inlet 102 is
provided in the apparatus. Disposed on bypass line 125 are
a control valve 127 and a flowmeter 128 to facilitate
regulation of the flow of water sample therethrough. Bypass
line 125 makes it possible to dilute a sample flowing through
line 93 with an additional amount of sample water after the
original sample has been treated with reagent through fluid
inlet 98 and the conductivity of the thusly treated sample
has been measured by conductivity cell 100. The purpose
of such an arrangement will be explained more fully hereinafter
i 20 in conjunction with an alternate mode of operation of the
apparatus.
The basic mode of operation of the device is as
follows. A water sample is passed through line 81 and
sprayed by means of spray head 82 into the upper chamber
84 of carbonating apparatus 83. At the same time, carbon
dioxide from source 88, which may be a tank of compressed
C2 passes through line 89 and enters chamber 84 beneath the
surface of the bed of separating media 87 disposed therein.
Carbon dioxide dissolves in the water sample as it trickles dcwn
through the separating media, whereby all more strongly
basic ions in the water react with the carbonic acid formed
by the dissolving CO2 to form bicarbonate ions, so that the
- 22 -

~04Z~87
pH of the samp]e is adjusted to a range of about 5 to 8,
most preferably from 7 to 8, and the total alkalinity of the
feed water sample is converted to a single ionic species.
The reaction with hydroxide ion may be visualized as follows:
2 2 ~ 2 3
H2C03 + OH ~ HC03 ~ H20
The reaction with carbonate ion is depicted by the following
equations:
C2 + H20 ~ H2C3
1~ H2C3 + C03 --~2HC03
A pH sensor 130 may be included in chamber 85 to monitor the
C2 addition. After the conversion of the total alkalinity
of the water sample into a single ionic species, namely
hicarbonate ion, the water sample will exhibit a substantially
uniform rate of change of conductivity upon the addition of
a given strong acid reagent thereto until the total alkalinity
of the water is exhausted. For nearly all waters containing
bicarbonate ion this rate of change is nearly constant and
amounts to approxima~ely .65 micromho per cm. per ppm. A
variable resistance may be included in the elec~ronic circuitry
of the analog calculator in order to adjust for other rates
of conductivit~ change should they be encountered.
~1here only a single species is likely to be
encountered in the water supply so that the rate of change
of conductivity upon the addition of reagent will be uniform
until the alkalinity of the water is exhausted, the carbonator
83 may be dispensed with and replaced by a simple constant
head device such as 23 in Figure 3.
The carbonated water sample gravitates into lower
chamber 85 where it accumulates until the depth of sample in
the chamber is equal to the height of partition 90 at which
- 23 -
: - ..

~04Z987
, time the e~cess amount flows over the top of the partition
and out discharge line 91. Sample water is continuously
withdrawn from chamber 84 through line 93. The rate of
flow through the line may be precisely controlled by adjusting
the head of the sample and also by means of valve 95. Flow-
meter 96 enables a precise determination of.the flow rate of
the sample. In the normal mode of operation, valve 127 is
maintained in the closed position so that none of the feed
water sample can bypass conductivity cells 97 and 100 and
fluid inlets 98 and 101.
The background conductivity of the sample is
measured by conductivity cell 97 and the resulting measured
value is passed via conductivity meter 1~6 to analog
calculator 109, and also is recorded by multiple chart
recorder 110.
Reagent reservoir 117 is filled with a strong
acid reagent, i.e. a solution of known concentration of an
acid which is essentially 100% in dissociated or ionic form
in solution. Hydrochloric acid is the preferred reagent
although other strong acids such as sulfuric or nitric may
also be utilized. The reagent concentration must be
maintained strictly uniform and must be precisely known.
Reagent pump 119 is,started so that a continuous supply of
the reagent is pumped to supply chamber 114. The reagent
then passes from supply chamber 114 through supply line 112
and fluid inlet 98 into the water sample flowing through
line 93. Valve 124 is opened so that reagent is also
transmitted through line 123 and fluid inlet 101 into the
water sample.
The rate of reagent addition may be precisely
controlled by appropriate selection of the size of the
- 24 -

1(~4Z9~7
capillary inlet orifices in fluid inlets 9~3 and 101 and by
appropriate regulation of the head of reagent in the reagent
supply system. Accordingly, a carefully controlled, known
proportion of acid reagent is added to the flowing sample
at each fluid inlet. An optional valve 131 may be in~luded in
line 112 to facilitate further control of the rate of flow
of the reagent. Valve 131 also allows the reagent supply to
be conveniently shut off so that the apparatus can be
cleaned.
The amount of acid added at fluid inlet 98 must
be sufficient to completely react with all of-the bicarbonate
present in the solution, thus the amount of reagent added
must be greater than the equivalent alkalinity of water
sample. A 20% excess over the maximum alkalinity is
preferred. ~n optional pH sensor 129 may be included on
line 93 to monitor the reagent addition. Most preferably,
sufficient acid reagent will he added to reduce the pH of
the sample to at least 3.5 so that ionization of the car~onic
acid produced by the neutralization of the bicarbonate ions
by the acid reagent will be suppressed. This prevents
distortion of the alkalinity measurement by ionization o~ the
carbonic acid. ~lkalinity determinations by conventional
colorimetric or potentiometric techniques must be corrected
for such distortion. For measuring the alkalinity of a
municipal water supply in the 10 to 200 ppm range expressed
as CaCO3 where the water sample flow rate was approximately
300 ml. per min., a .3 ml. per min. reagent flow rate oE 3
Normal hydrochloric acid at each injection point is satis-
factory.
Mixing chamber 99 is provided in order to ensure
complete ~ixing of the water sample and the added reagent
- 25 -

987
A suitable mixing cha~ber may comprise the body of a lO0
or 200 ml. pipette with a glass bead inserted therein. After
complete mixing of the sample and reagent and complete
neutralization of the alkalinity of the sample, the
conductivity of the reagent treated sample (E2) is measured
by conductivity cell 100. As with the first conductivity
measurement, the result is passed to the electronic analog
calculator 109 and is also recorded by recorder llOu
A~ter the second conductivity measurement by cell
lO0, a second increment of acid reagent is added to the
sample through line 123 and fluid inlet lOl. As with the
first increment o reagent, the second reagent must be a
carefully controlled known amount. It is preferred that the
second increment of reagent e~ual the first increment inas-
much as this simplifies the subsequent computations and
consequently allows the use of a simplified calculating
device. Thus in the preferred apparatus, .3 ml. per min. of
3 Normal IICl is added at each acid reagent fluid inlet. If
equal increments are not utilized, the second increment~of
reagent should be between one and two times the first.
Mixing of the second reagent increment with the
sample is accomplished by means of a second mixing chamber
103 which is essentially identical to mixing chamber 99.
After complete mixing of the second increment of reagent,
the conducti~ity is measured a third time (E3) by
conductivity cell 104 and the result is transmitted to
calculator lO9 and also recorded by recorder 110. The
water sample then passes to discharge 94.
Small amounts of CO2 gas are liberated in the
system as a result of the reaction of the acid reagent with
the bicarbonate ion. In general, the amount of gas is
- - 26 -

~09~Z987
insufficient to interfere with the measurement of the con-
ductivity of the sample by conductivity cells 100 and 10~,
but the accumulation of the gas bubbles inside the system
must nevertheless be prevented because an accumulation of
gas could cause irregula~ities in the sample flow.
Accordingly, the segment of the feed water sample flow line
93 which includes fluid inlets 98 and 101 and conductivity
cells 100 and 104 is oriented in a vertical direction and a
vent 105 is provided at the upper end of the vertically
oriented segment.
The diameter of line 93 should be sufficiently
large to allow air bubbles to be carried therethrough in
order to prevent air blockages. An inside diameter of 3/16
inch is satisfactory. The diameter of the line should not
be so large, however, that at ordinary rates of ~low on the
order of 300 ml. per min., the linear velocity of the sample
becomes inordinately low. Under most circumstances a line
having an inside diameter greater than 3/8 inch should not
be used.
The rate of change of conductivity of the water
sample after complete neutralization of the original
alkalinity can be determined by ~he calculator from the
second and third conductivity measurements. The hydrogen
ion activity, and therefore the rate ~f change of
conductivity of the sample after neutralization of the
alkalinity thereof, is significantly affected by the back-
ground conductivity due to the presence of ions of neutral
salts in the sample~ By directly measuring the conductivity
of the sample before and after the addition of the second
increment of reagent, it is possible to compensate for such
effects. Thus the background conductivity due to the
- 27 -

104Z987
presence of neutral salts such as sodium chloride or
: sulfate up t~ concentrations of about 800 parts per millionhas little or no effect on the alkalinity measurements made
with the instant apparatus.
The total alkalinity of the original water sample
may be computed from the amounts of acid reagent added in
each increment, theinitial background conductivity measured
by cell 97, the rate of change of conductivity prior to
neutralization of all of the alkalinity of the original
sample, and the rate of change of conductivity after complete
neutralization of all the alkalinity of the original water
' samples and the rate of flow of the water sample through the
system. In applicantS' preferred embodiment this may be
achieved by utilizing an analog computer designed to solve
the equation
( 3 X2) (Eo E3) - (X3) (Eo - E2)
X=
Mi (X3 - X2) - (E3 E2)
where X is the alkalinity of the water sample, Eo is the
initial background conductivity of the water sample measured
b~ conductivity cell 97, E2 is the conductivity of the sample
after the addition of the first increment of acid reagent
through fluid inlet 98, E3 is the conductivity of the sample
: after the addition of the second increment of acid reagent
through fluid inlet 101, X2 is the concentration of acid in
the sample after the addition of the first incre~ent of acid
reagent through fluid inlet 98, ~3 is the concentration of
acid in the sample after the addition of the second incremen~
of acid reagent through fluid inlet 101 and Mi is the initial
rate of change of conductivity of the water sample upon the
addition of acid reagent prior to neutralization of the total
. . .
~ 28 -

~L~4Z9~37
alkalinity. Conventional commercially available analog
computer components may be readily assembled or arranged
into a system adapted to perform such calculations. Indeed,
any of several approaches may be followed to achieve the
desired result, and a wide variety of arrangements of
electrical circuitry could be developed to perform the
necessary calculations.
Figure 6 illustrates one such arrangement. The
three measured conductivity values are first passed through
a filter network to reduce the noise level of the signals.
The equation numerator and denominator are than seplarately
developed by operating amplifier stages and then are passed
to a divider module for calculation of tha final value. An
attenuation stage may be provided to match the divider output
; to thè output device or recorder. The acid concentrations
are represented in the amplifier circuitry by appropriate
resistances. Fixed resistances may be utilized if the acid
concentrations remain relatively stable, but the use of variable
resistances allows for precise calibration of the apparatus.
A variable resistance (slope adjustment) 131 is also provided
to adjust the rate of change of the conductivity of the
original water sample upon the addition of reagent. The
proper setting may be determined by titrating the alkalinity
of a sample by conventional procedures and then adjusting the
; variable slope resistance until the output value (X) from
the calculator equals the titrated value. Dummy inputs are
provided for checking the calculator. Commercially available
~ amplifiers and divider module components may be utilized.
;~ In the arrangement illustrated in Figure 6, the follower
ampli~iers are one-half Signe-tics No. 5558, the operational
eedback amplifiers are type ~ A741 and the divider module is
~ .
- 29 -

~042987
an ~ntersil No. 8013. An optional range switch may be
included to set the calculator for whatever range of
conductivities may be encountered in the system~
The calculator generates a continuous output
signal directly proportional to the alkalinity of the original
sample. The resulting alkalinity value is ~then passed to
output device lll and is also transmitted to recorder llO
where it is recorded on a strip chart. The output may be
utilized to control the addition of treatment chemicals to
the water supply, to set off an alarm or to shut down
apparatus when prescribed limits of alkalinity are exceeded.
Increased sensitivity is possible because the
apparatus takes advantage of the high mobility and conductivity
of hydronium and hydroxide ions in aqueous systems.
The calculator may also be designed to shut down
the monitor and/or set off an alarm in the event of a failure of the
reagent supply system. This is most readily effected by
carrying out a direct comparison of the second and third
conductivity measurements. The addition of more reagent or
the dilution of the reagent treated sample will result in
or change in the measured conductivity. Therefore if E3
equals E2, it is an indication that the reagent supply
system is not functioning, so that the monitor should be
shut down. A sudden change of (E3 - E2) may also indicate
failure of the reagent supply system.
In an alternative mode of operation, valve 124 is
closed and the flow of acid reagent through fluid inlet 98
is increased until it is approxi~ately eq~ to the ~ined reagent
flow through inlets 98 and lOl in the normal mode of
3a operation~ i.e. about ~6 ml~ per min. Valve 127 is opened so
that a poxtion of the ~oiler feed water sample bypasses fluid
- 30 -

~0429~7
inlet 98 and conductivity cell 100 and enters the main sample
flow line 93 through fluid inlet 102. By means of valves 95
and 127 and flowmeters 96 and 128 the relative proportion of
the sample passing through each of the respective lines, and
consequently the dilution of the sample flowing through the
maln sample line 93 by the portion of the sample flowing
through bypass line 125, may be controlledO Preferably they
should be equalized. By substituting the conductivity value
measured by conductivity cell 104 for the conductivity reading
taken after the addition of the first increment of acid
reagent in the normal mode of operation and the conductivity
reading taken by conductivity cell 100 for the conductivity
value measured after the addition of the second increment
of acid reagent in the normal mode of operation, the deter-
mination of the total alkalinity of the water sample may
be effected in substantially the same manner as previously
described for the normal mode of operation. The substitution
of conductivity values may be effected by switching ~he wires
connecting conductivity meters 107 and 108 to the electronic
calculator 109 or by means of a changeover switch. The
concentration of acid after the addition of reagent should be
substituted for the concentration of acid after the addition
; of the second increment of acid reagent in the normal mode
of operation and the concentration-of acid after dilution of
the sample flowing through line 93 with sample from bypass
line 125 should be substituted for the concentration of acid
after the addition of the second reagent increment in the
normal mode of operation. The acid concentrations are
readily derived from the initial concentration of the reagent,
the rate-of flow of reagent through supply line 112 and the
rates of flow of the water sample through lines 93 and 125.
- 31 -

~1)4Z9~7
The foregoing apparatus is also useful for
determining the acidity of weakly acidic solutions, such as
boric acid, by using an alkaline reagent such as sodium
hydroxide (NaO~) and making similax conductivity measurements.
The foregoing apparatus having a sample flow rate
of approximately 300 ml. per min. and utilizing 3 Normal
hydrochloric acid reagent at a flow rate of .6 ml. per min.
and conduc~ivity cells having cell constants of 10 is
specifically adapted to monitor the alkalinity of a municipal
water supply in the range of 10 to 200 ppm expressed as CaCO3.
By decreasing the reagent concentration and by utilizing
conductivity cells with smaller cell constants ranging down
to about 0.10, the apparatus may be readily modified to
measure alkalinities in the 0 to 10 ppm range expressed
CaCO3. Thus the apparatus may also be used for monitoring
the alkalinity of cooling tower water, boiler feed water, or
turbine condensate.
In the apparatus of Figure 5, no special means are
required for temperature control because at the flow rates
utilized, i.e. approximately 300 ml. per min. aample and .6
ml. per min. reagent, only minimal temperature changes occur
in the sample in passing through the apparatus.
The efficacy of the invention is further demon-
strated by the following tests:
Test II
Water samples from the Vermilion Generating
Station of the Illinois Power Company in Danville, Illinois,
were analyzed for alkalinity by adding a controlled excess
amount of strong acid and measuring the ~lectrical conductivity
(~1~ An identical amount of acid was added to a sample of
de-ionized condensate and the electrical conductivity (QO) was
- 32 -

16)4Z9~37
m~asured to provide a standard value for comparison. The
differential conductivity (a Ll) was determined by
subtracting the measured conductivity of each sample from
the standard value. Thus ~ Ll = ~O ~ Ql The alkalinity
; expressed in terms of milligrams of CaCO3 per lltre was
calculated from the a Ll value for each sample. For
~'~ comparison purposes the alkalinity of each sample was also
determined by conventional colorometric titration procedures.
The results of the tests are listed in Table II.
Table II
Sample Source Differential Calculated Titrated
Con~uctivity A~;alinity Alkalinity
~ L mhos mg. CaCo3/~ Mg. CaCO3/~
Main stèam 5.00 .56 .56
Main steam 5.75 .64 .58
Turbine Cond.
Steam 4.00 45 45
Feedwater 8.40 .93 .9
Test III
The alkalinity of turbine condensate from the No.
~ Turbine of Ridgeland Station o Commonwealth Edison at
Stickney, Illinois was continuous monitorea using apparatus
of the type disclosed in Figure 5 by withdrawing a continuous
sample, measuring the electrical conductivity of the sample
(Eo)~ adding a controlled excess amount of acid to the sample
and mixing, measuring the conductivity of the sample with
the acid (E2), adding a second controlled amount of acid
and mixing, and again measuring the conductivity of the sample
(E3). The measured conductivity values were fed to an analog
computer programmed to solve the equation
3 2) (Eo E3) - (X3) (E3 - E2)
X= -- .
) (X3 ~ X2) (E3 2)
- 33 -

1~14ZS~7
where X is the differential conductivity equivalent of the
alkalinity, X2 and X3 are the acid concentrations after the
first and second acid additions, Mi is the initial rate of
change of conductivity of the sample upon ~he addition of
acid, and Eo~ E2 and E3 are the measured conductivity
values. The measured conductivity values and the calculated
alkalinity were continuously recorded on a multiple chart
recorder. A representation of a two hour segment of a
chart covering an interYal from 10 a.m. to noon is shown in
Figure 7. The figure shows a gradual increase in alkalinity
from about 1.33 ppm (expressed as CaCO3) at 10:00 a.m. to
about 1.40 ppm at noon. The sharp discontinuity in the
recorded values at about 11:30 a.m. was caused by the taking
of a sample for laboratory confirmation by conventional
colorametric titration techniques. The laboratory test yielded
an alkalinity of 1.37 ppm CaCO3 as compared to a value of 1.36
ppm CaCO3 determined according to the invention.
Test IV
The alkalinity of tap water from the Champaign-
Urbana, Illinois Municipal Water Supply was continuously
monitored at a remote monitoring point in the distribution
system with the apparatus of Figure 5 according ~o the
procedure described above under Test III, Champaign-Urbana
Municipal water is lime softened and post-treated with
sulfuric acid to prevent clogging of the sand filters and
deposition of excess calcium carnonate in the distribution
system. A disruption of the acid feed system at the
treatment plant was later detected at the remote monitoring
point by an increase in pH and a corresponding decrease in
alkalinity. Figure 8 shows measured conductivity values and
calculated alkalinity for a five hour time interval from
6 a.m. to 11 a.m. The figure shows that the alkalinity
- 34 -

~L04Z9~517
maintained a relati~ely stable level of about 107 ppm
(expressed as CaCO3) from 6:00 to 8:00 a.m. The alkalinity
then started to drop and reached a minimum value of about
90 ppm between 9:15 and 9:30 a.m. Thereafter the alkalinity
started to rise gradually toward normal levels, reaching a
value of about 103 ppm at 11:00 a.m. To confirm the
results, samples of the water were taken at about 8:~7 a.m.
and 8:~8 a.m. and titrated by conventional colorimetric
techniques to a methyl orange endpoint. The titration of
the first sample yielded an alkalinity of 95 ppm which
correspond exactly to the alkalinity measured according to
the invention. The titration of the second sample yielded
an alkalinity value of 93 ppm which likewise corresponded to
the alkalinity measured accordin~ to the invention.
The foregoing arrangements have been described
merely as illustrations of the apparatus of the invention.
The invention is not limited to use in steam generator systems
or nuclear reactors or even aqueous systems in general, but
is applicable for measuring the presence of weak acids or
bases in liquid systems of all types. Modifications of the
invention undou~tedly will occur to those skilled in the
art, therefore, the scope of the ~nvention is to be limited
solely by the scope of the appended claims.
- 35 -