Note: Descriptions are shown in the official language in which they were submitted.
S~3~
g This invention relates generally to the preparation
of pigment grade iron oxides and more particularly, to the pre~
paration of pigment grade Fe2O3 from waste ferrous sulfate by a
roasting process.
In the past, waste ferrous sulfate has presented a
problem to many lndustries. In particular, waste ferrous sulfate
is produced from pickling plants and from the production of
titanium dioxide by tne sulfuric process as a by-product and its
discharge and disposal creates many problems including ecological
and handling problems for these industries.
The neutralization of this waste product is costly
and generally results in unsaleable products, which also raises
storage problems. For many years, processes have been proposed
involvin~ roasting of the iron sulfate with the formation o~
sulfur oxides which can be recycled for the production o~ sulfuric
acid, but the ferric oxide also produced by the roasting is
coarse and possesses inadequate pigment grade properties (see for
example, German Patent No. 921,264). The production of sulfuric
acid by this method is only competitive if the iron oxide which
~O accompanies it is a high quality product which is utiliza'~le on
the market, such as with red Fe2O3 pigments with good colour
purity.
However, the iron sulfates with whicll this invention
is concerned generally contain metallic impurities which, when
roasted, com~ine with the iron oxide and lower its colour purity.
More recently, several processes have been proposed
which are designed to eliminate these impurities. For example,
re~erence is made to German Ausle~eschxift serial number
~ 2~8 (published on ~ovember 28,1963) whicll recites a process
which includes roasting to convert 80 to 95% of the iron sulfate
to the oxide, followed hy washin~, in the course of which certain
~5~a3~
1 cations such as ~n, which remain in the form of soluble salts,
are eliminated. Following this treatment, pure ~ Fe203 oxide is
effectively obtained, but it only has mediocre pigment properties,
owing to the fact that the roasting time/ternperature combination
required to elimina-te the harmful cations fails to i~part
optimum dimensions to the oxide particles. Moreover, pigment
preparatiOn is not the object of the German Ausleaeschrift
serial nu~ber 1 144 248, as the purified ~ Fe2O3 oxide serves as
a base for the subsequent preparation of ~ Fe203. Similar ob-
servations can be made in connection with US Patents 2,184,738
and 2,416,138.
A further process also has been proposed ~see French
Patent Number 2,296,671) in which the harmful metallic cations
are eliminated by partial roasting followed by washing. I-lowever,
this process applies to a raw material other than iron su7fate,
jarosite. Moreover, the achievement of well defined pigment
; yrade properties is subject to the precise adjustment of the
partial pressure of SO2 or oxygen in the ~urnace, and this is
di~ficult to achieve on an industrial scale.
Accordingly, it is an object of the p~esent invention to
at least partially overcome these disadvantages by providing a
process for converting a previously-k~own pollu-tant by-product
into a saleable product.
It is a ~urther object of this invention to provide a
process for converting iron sul~ate to a commercially usable
pigment grade iron oxide.
It is a still further o~ject of this invention to
provide a pigment grade iron oxide from waste ferrous sulfate.
To this end, in one of its aspects, the invention
provides a process for produci~g red Fe2O3 pig~ents from
3~
1 E'eSO~ 7 H2O which comprises roasting partly dehydrated ancl
granulated FeSO4 7 H2O, washing the resulting product, followed
by pigmentary calcination and cru.shing.
In another of its aspects, the invention furtller
provides a process for producing red Fe2O3 pigments from
FeSO4 7 lI2O which comprises (a) roasting partly dehydrated
and granulated FeSO4 7 H2O to convert 90 + 5% of said
FeSO~ 7H2O to the oxide in the presence of a reducing agent
in an externally heated furnace in which the roasted material and
the roasting gases are collected continuously at the same end of
.said furnace, said reducing agent being added in an amQUnt between
0.1 and 2 times the stoichiometric amount; (b~ subjecting the
resultant product to a washing treatment without mechanically
destroying said granules, said washing comprising the steps of
washing with wa~er, treating with a hot alkaline solution, then
washing with water; (c) sub~ecting the resulting pxoduct to
pigmentary calcination in a furnace flushed by a gas flowing in
a countercurrent dlrecti.on to said iron oxide at a temperature of
between abaut 750C. and about 1000C.; (d) crushlng the
resulting product.
In yet another of its aspects, the invention further
provides red Fe203 pigments with orange-red to purplish-red
tonality characterized by the fact that they exhibit an oil
absorption lower than 12.5.
Further objects and advantages o~ the invent.ion will
appear from the following description.
The objects o~ tl~e present invention may be achieved
by subjectincJ the waste ferrous sulfate to double roasting with
intermecliate washing, followed by crushing and if desired,
micronization,
LSit~3~
1 The term double roasting refers to a process which in-
cludes an initial roas~ing, which may be conducted in the
presence of a reducing agent, carried out on partially dehydrated
FeSO4 7H2O , washing of this roasted product, followed by a
second roasting - corresponding to pigmentary calcination of
the residue from the previous operations. The final result is a
red Fe2O3 pigment dis~inguished by excellent pigment grade
characteristics. The first roasting is per~ormed so that about
90% of the iron sulfate is converted to the oxide; the second
roasting or pigmentary calcination is performed at temperatures
ranging from about 750C. to about 1000C.
A preferred embodiment of the invention will now be
described.
Ferrous sulfate is generally available in the form of
the heptahydrate. The direct introduction o~ this salt into a
furnace raises problems because, by melting at less than 100C.,
it easily forms crusts which are detrimental to the satisfactory
operation of the furnace. Hence it is pre~erable to feed the
roasting furnace with a partially ~e}lydrated salt, particularly
the monoh~drate. The latter should be available preferab:Ly in
the form of granules which are 0.5 to 3 mm in diameter.
Roasting is carried out preferably in an externally
heated furnace in order to avoi~ dilution of the sulfur oxides
~SO2r SO3) by combustion gases tco2, N2, excess 2) so as to
enable their use for the production o~ sul~uric acid. It may be
assumed that t~le reaction occurs as follows:
2FeSO4 x E20 ~ Fe203 ~ S02 3 2 (l)
The temperature/~urnace residence time combination is
selected so that about 90 ~ 5% of the iron present is converted to
the o~ide, the rest remaining in soluble form. This is a com-
promise whereby almost all the harm~ul impurities such as Mn, Mg
-- 4
3~
1 and Co remain in soluble form, while achieving a satisfactory
conversion yield to Fe2O3. This result is obtainecl at -temperatures
ranging ~rom about 650 to about 800C., and residence times
ranging from about 10 minutes to about 10 hours.
Roasting is improved if a certain amount of reducing
agent (hereinafter referred to as R) is incorporated with the iron
sulfate, such as carbon, sulfur or a llydrocarbon. The role of
the reducing agent is to shit the equilibrium relation (1)
to the right by the elimination o-f SO3 by a reaction of the type:
SO3 + R- ~ So2 + RO (2)
It is recon~nendea that the quantity of reducing agent
used be between 1 and 1.5 times the stoichiometric amount. A
particularly advantageous reducing agent is sulfur. In this
case, the roasting reaction becomes:
4FeSO4 x H2O + S -~2 Fe2O3 + 5SO2 f 4 ~ H2O (3)
Within the limits of unavoidable air infiltration into
the furnace, it can be seen that the use of sulfur helps to obtain
gases which are especially rich in sulfur oxide because, due to
the use of an indirectly heated furnace, the only diluent is
2~ water vapourO The advantage offered by the use of a reducing
agent resides in tlle fact that the roasting temperature is
lowered by some 100C., thus lengthening the service life of the
refractory metal which is used to line the furnace interior to
acilitate heat transEers. Another advantage lies in the pro--
duction of a non-oxidizing atmosphere, which also enhances the
behaviour oE the metallic lining. The use of sulfur is also
especially advantageous because, apart rom its beneficial
efEect on the hea-t balance, the costs of additional raw materials
ar~ offset by the corresponding sulfuric acid obtained.
The solids and gases should preEerably be in concurrent
1 flow in the roasting furnace, so that the sulfur which is dis-
tilled at the furnace inlet is able to oxidlze in contact with
the solids, or in the ~as phase itself before being able to
escape.
The substance obtained at the furnace outlet occurs in
the form o~ granules with dimensions approaching those of the dry
iron sulfate charged initially into the furnace, and mainly
contains Fe2O3 accompanied by about 10% iron remaining in the
soluble state. The harmful impurities such as Mn, Mg and Co
remain in soluble form. After purification, the sulfur oxides
leaving the furnace are recovered for the production of sulfuric
acid.
The roasted product is washed with water, but in order
to obtain neutral pigments more easily, it is more advantageous
to supplement this washing by hot alkaline treatment, for example
with 0.1 N caustic soda, followed by a second washing with water.
Washing may pre~erably be carried out in a stationary bed with
upward water flow, or more preferably, on strip filters and, in
a more general manner, with any suitable system which does not
subject the granules to mechanical stresses which are liable to
destroy them.
After washing and drying, the iron oxide generally con-
tains over 97% Fe2O3. The only impurities remaining in signifi-
cant proportions are Ti (in tne case of iron sulfate from
ilmènite) and S. ~`he latter is eliminated by the final calcin-
ation of the oxide. The presence of Tio2 up to concentrations
o~ 2~ is not detrimental for the pigment grade properties oE
the finished product. The washed and dried prod-lct obtained at
this stage still only possesses very inadequate pigment grade
3~ properties, because the oxide particles are not yet of suitable
-- 6 --
si,ze. It i5 well knowil that particle size is an important factor
influencing pigment characteristics.
The second roasting which plays the role of pigmentary
calcination is advantageously performed in a directly heated
furnace, but any other furnace allowing gas flow above the
product is suitable. The gases and solids should preferably be
in countercurrent flow in this furnace, so as to evacuate the
waste sulfur oxides satisfactorily, and thus to ensure that tlle
finished product has satisfactory pH and resistivity. The tem-
perature and residence time are selected in order to obtain the
desired red pigment shade: lower temperatures (750 - 820C.
yield small orange-red crystals, and higher temperatures
(900 - 1000C.) yield larger purplish-red crystals. Neutral red
tints, lying between orange-red and purplish-red, are obtained
at intermediate temperatures ~820 900C.~. ~ particu]arly
interesting pigment range is obtained by calcination for 1 to 10
hours in the interval 750 - 1000C.
At the outlet of the calcination furnace, the product
is cooled and undergoes crushing in routine conditions prevailing
in the inorganic pigment industry. Micronization can be used to
supplement grinding, to ensure excellent dispersibility of the
pigment in binders, and greater brilliancy of the lacquers pig-
mented with this oxide.
This invention thus solves the ecological problem raises
by waste iron sulEate, because it permiks its utilization for the
production of sulEuric acid and high pigment grade iron oxide.
One advantage o~ the process is that it produces a ~ide range of
red pigment tints by means of variations in a parameter which is
easy to control; that is, the final calcination temperature.
The elimination of harmful impurities by the process also offers
3L5~3~
1 the advantage of giving these pigments a colour purity whicll
ma]ces them at least comparable to the best red pigments available
on the market. The pigments thus obtained have a colourant power
equal to or greater than currently marketed Fe2O3 pigments.
Other charact~ristics of the pigments produced by the invention
process are far superior to those of existing pigments. Thus oil
absorption represents less than half of that of available pig-
ments: this of~ers the user an economic and ecological benefit,
because he can consequen-tly use less solvent in paints containing
this oxide, while obtaining the same visc~sity. The cl~emlcal
composition of the pigments is another important advantage of
this invention. Using iron sulfate produced by the titanium
pigment industry, the only imp~rity which can remain in a signi-
ficant concentration is ~iO2. As it so happens, TiO2, within the
2~ limit encountered in practice, is not harmful to colour purity.
Tllis is particularly important if the pigments obtæined
are used to colour foodstuffs, packings and plastics~ These
pigments are subject to maximum concentrations of toxic imp~rities
established for foodstuffs, by various governmental authorities.
For example, in France, these are set by Article 8 of the Decree
of 15 October 1964 published in the Journal Officiel dated
4 November 1964. The purification treatment inherent in the
invention contributes to eliminate some of these impurities con-
tained in the waste iron sulfate which served as a raw material,
so that the pigments obtained largely satisfy the legal purity
requirements, whereas these limits are sometimes exceeded in com-
rnercially available pigments. The fact that the red pigments
produced by the invention porcess satisfy legal purity requirements
for their use in foodstuffs is a significant advantage over pig-
ments currently available on the market.
3~2
1 These different advantayes are illustrated by the
following examples. Most testing ~ethods employed are standard
practice forprofessionals.
However, some of them have been specially developedand are clarified below.
For iron oxides, the determination of certain colouri-
metric properties is more sensitive if, ins-tead of pigmen-ting
resin with pure Fe203, a mixture of pigments is added to the
resin, this mixture consi~ting in the same Fe203 with a Tio2
pigment in given proportions.
This gives rise to so-called "shaded off" paint in
which the TiO2 plays the role of enhancing the colourimetric
characteristics of the iron oxide. ~he rate of shading is defined
by the weight ratio Fe~03 / Tio2 ~ Fe203. ~11 the comparative
tests were performed with a shading rate of 25%. The use of a
second pigment such as TiO2 in addition to ~e203 is also necessary
to determine the tinting strength of this Fe203. The tinting
strength may be defined by the equation:
TS = 100 x 25
~ .
where-t is the shading rate which must be used with the test
sample for the corresponding paint, checked by means of a colouri-
meter, to have the same Y filter raflectance as the reference
piyment to whicll it is compared, the latter itself contained in
a 7.5~ shaded paint. For example, in order to obtain the same Y
tint inte~sity as the re~erence oxide in the 25% shaded paint,
the sample must be shaded off by Z2%, so that the tining strength
of this sample in comparison with the reference is:
100 ~ 25 = 113.6%
22
_ 9 _
32
In a qualitative manner, thls may be summarized by
saying that a sample of red has greater tinting strength if it is
mixed in smaller amounts with a given mass of TiO2 to obtain the
same reference pink.
Another important characteristic of a pig~ent is the
colour deviation (~C) which it exhibits in comparison with
existing good quality products. A new oxide is considered to be
satisfactory if, in;relation to one of the existing commercial
grades, it exhibits colour deviation not exceeding the limit
corresponding to measurement accuracy ~or ac about 1.5) and if,
moreover, its tinting strength is greater than or equal to that
of the known pigment. Colour deviations ~C taken into considera-
tion in the following examples have been established as follows:
alkyd resin base paint samples are prepared with a 25~ shading
rate with each of the known oxides, and the corresponding tri-
chromatic coordinates X,Y, Z are measured. Using the same
formulation, the pigment obtained by the invention process is
added to the binder, and -the reflectances are measured with tri-
stimuli filters X, Y, Z. The colour deviation ~C is then
determined ~ in MacAdam units, National ~ureau of Standards,
Draft Standard ASTM D 2244-64T) between the sample and the dif-
ferent known oxides. Among known pigments, the one against which
the oxide prepared by the invention process can be compared is
the one which most closely approaches i-t in chromaticity, i.e.
the one which exhibits the smallest colour deviation in relation
to it~ This determination of the known pigment which most closely
approaches a given sample re~uires time-consuming calculations
which we carried out successPully with the use of a microcomputer.
If ~C is lower than 1.5~ it is considered that the difference
3~ between the sample and the reference is insignificant, i.e. that
-- 10 -
1 the colour purity of the sample is as good as that of the
corresponding pigment existing on the market. All comparisons
presented in the examples deal with pigments prepared in accordance
with the state of the technique, or by the invention process,
with their commercial co~nterpart with the nearest chromaticity.
One of the particularly interesting elements of this comparison
is the value of the Z component given by the colourimeter,
because this is characteris~ic of the tonality of the red obtained.
With 25% shading, quality pigments currently available on the
market cover an interval ranging from about Z = 15 (for orange
tonalities) to Z = 38 (for the most purplish tonality~.
The dispersibility of the pigments, expressed in microns,
is measured by a North gauge after 5 and 30 minutes of crushing
of the oxide in alkyd medium, in the presence of 4 mm diameter
glass balls. The lower these values, the better the fineness
of the crushing and hence the dispersibility.
The pH of the pigments is measured in accoxdance with
AFNOR Standard T 30-035. It is generally considered that pi~nents
of which the aqueous extract has a pX from S to 9 are satisfactory.
The aqueous sùspensions obtained by working in accordance with
this Standard have also served to determine indirectly the
soluble salt content o~ the finished product. ~o do this, the
resistivityof the aqueous extract is measured: the higher the
resistivity, the lower the soluble salt content.
Oil absorption is determined in accordance with AFNOR
Standard T 30-022. The fi~ures expressin~ the oil absorption
represent the rate o oil required to obtain a firm, smooth paste
with 100 g of pigment.
Brilliancy is measured with a Zeiss GP 2 brilliancy
meter, at an angle of incidence of 20 , on OVen-baked alkyd paints,
-- 11 --
g with a volumetric pigment concentration of 16. The higher this
figure, the better the brilliancy.
Exampl_ l
The raw material employed was a ferrous sulfate ob-
tained from Tio2 production by the sulfuric me~hod, characterized
by a Mn/Fe2O3 ratio of 0~63%. Its more complete analysis is the
following:
FeSO~ 7H2O 94% Fe 19% SO4 34.75~
Mn 0~18~ Ti 0.13% Mg 0.20% Zn 0.02%
Co 0.003%
An iron oxide free of solubilizable impurities was
prepared in accordance with the German Patent ~ No.
11 44 248. The previously dehydrated salt aggregated in 3 mm
diameter granules was roasted until a conversion rate to Fe2O3
of 91.7% was obtained; roasting lasted 15 minutes at 800C. The
roasted product was subjected to intensive washing with water,
dried and crushed, then subjected to tlle series of pigment and
analytical tests. The results are given in Table l (example l,
Column e). It may be seen that the chemical purity is satis-
~actory. On the other hand, certain essential pig~ent yradeprop~rties are clearly deficient. The comparison with an existing
range of commercial high quality red p~gments shows that the
~ ,~bl/'cc2f.c~1
sample prepared by the German Patenti~}h~x~ ll 44 248 most
closely resembles the most orange pigment (Z = 14) (Column h), but
that, even in comparison with this pigmellt, it exhLbits a high
chromatic deviation ( ~C - 2.6). The procedure described in this
patent fails to produce p:igments characterized by Z values higher
than about 14~ The neutral or purplish reds are therefore un-
obtainable. It may also be observed that the pll falls outside
the standard limits, and the soluble salt content is fairly hi~h,
- 12 -
3~
1 so that the oxide thus obtained fails to meet the objective set
in this invention.
Example 2
FeS04 7H2O from the same source as that of Example 1
was partially dehydrated and granulated in a Niro Atomi~er
(Copenhagen) spray granulator. The 1 to 3 mm diameter FeS04 H20
spherules obtained were introduced by a worm screw continuously
at the rate of 4 kg per hour into a 2 meter long horizontal
rotary furnace. The solids travel in a 20 cm diameter NS 30
refractory steel 'tube, externally heated by gas by means of a
Meker burner rack subjected to automatic temperature control. The
partially roasted iron sulfate and roasting gases are withdrawn
at the same end of the furnace. The average residence time of
the solid in the furnace is 1. 5 hours The furnace temperature
was regulated to 790C. The oxide obtained was crushed and sub-
]ected to di'fferent tests. The resul~s in Table 1 show that the
commercial pi~ment most closely approaching this oxide is char-
acterized by a Z of 17.5 with 25% shading. In comparison with
this commercial oxide, the pigment prepared in Example 2 exhibits
a large chromatic deviation (AC = 3.9) which reflects the lack
of purity caused by foreign cations. Furthermore, this oxide has
a sharply acidic pH and a high soluble salt content. It may ~e
noted that owing to its high Zn content, this oxide does not meet
the maximum concentrati.on requirements imposed by the Decree of
15 October 1964. The product thus obtained is consequently'not
a quality pigment.
Exam~le 3
Ferrous sul~ate from the same source as that used in
Examples 1 and 2 was dried and granulated as indicated in Example
2. The granules were mixed with crushed sulfur in the ratio
- 13 ~
~s~
1 S/FeSO4 H2O = 5%. This mixture was introduced continuously
by means of a suitable worm screw into the roasting furnace
already used in Example 2. The furnace temperature was 670C.
and average residence time was 1.5 hours. The fraction
insolubili~ed Fe/total Fe was 91%. The roasted granules ~ere
placed on a Buchner, where they under~7ent washing by upward water
flow up to total elimination of the soluble iron. The product
was then placed in contact with boiling 0.lN caustic soda, and
then washed again with water~ The washed product was oven dried
and then calcined in a second horizontal furnace pro~ided with
vigorous countercurrent air flushing. The temperature was 820C,
average residence time was 1-1/2 hours, and the washed and dried
oxide feea rate was 2 kg/hour. After cooling, the oxide was
crushed in a ball mill and micron.ized.
Table 1 shows that the pigment obtained has a chroma-
tlcity closely approaching ~ C - 0.6) that of a commercial
quality pigment with a tonality leaning towards orange ( Z = lS).
However, the tinting strength of the sample prepared by the
invention process is greater (113). The oil absorption of 10.1
ZO is much more favorable than that of the similar pigment available
on the market ~28~. A clear advantage ~n bri.lliancy can also be
observed. Very large diferences also appear in harmful element
contents, for which maximum allowa~le limits in pigments intended
for colouring foodstuffs are established by the ~inisterial
Decree of 15 October 1964. Contrary to the corresponding com-
mercial p.igment, the impurity concentrations of the oxide in
Example 3 are lower than the maximum concentrations. (mhese
maximum concentrations are noted in the right-hand column o
Tables 1 and 2).
Thus, it may be seen that the pigment prepared by the
- 14 -
3~
1 inventlon process exhibits significant advantages over a
corresponding good quality pigment currelltly available on the
marketO
Example 4
Example 3 was repeated except that the only difference
was that the temperature of pigmentary calcination was 845C.
instead of 820C. The chemical and pigment grade characteristics
of this sample, shown in Table 2, show that, as in the previous
example, the slighly orange-red pigment obtained offers significant
1Q advantages over its equivalent known before the invention .
Example 5
Examples 3 and 4 were repeated except that the only
difference was that the pigmentary calcination temperature was
~80~. The pigment obtained was crushed in a ball mill but not
micronized. T~is yielded a red pigment offering the advantages
already mentioned in Example 3 over a standard pigment (see
Table 2).
Example S was repeated except that the calcination tem-
2~ perature was 960C. The pigment thus obtained i5 a clearly
purplish-red, corresponding to the other extreme of the Fe2O3 reds
on the market. ~ere again, Table 2 shows the many charac-teristics
for which the pigment produced by the invention process is
superior to its known equivalents.
-- 15 --
~:3hs~3~
Table 1
. characteristlcc Example 1 ~ Example 3 (~)
. _ . . ~_ . .. __. ___ ~
e h e h e h corcen~
.~ . _ _ _ ~ _ ~ tra~ion~
A : shaded off 21.9 25 26.1 25 22.2 25
B : coordinates .
Y 22.9 22.9 20.0 20.0 21.0 21.0
X 30.2 29.6 25.4 26.0 27.9 27.8
Z 13.0 ~.4.0 15.~ 17.5 ~.5.1 15.0
. . _ , _ _ - . -.-.- ------I
C . chromatic
deviation~C 2.6 3.9 0.6
__ .___ . , ...
D : tinting
strength 114100 96 100 113 100
E : oil
absorption 2S.429 10.5 26 10.128
F : brilliancy 29 21 28 30 58 20
G : fineness in
5 min 95 75 90 65 80 80
30 min 40 37 35 35 35 40
}I : pH 2.67.4 2.9 5.7 6.37.5
I : resistivity 0.77.2 1.0 5.1 4.67.0
kohm ~ cm
_ ._ ._, _ _ _ ._ ._ __ _
% Fe2O3 96.196 96.0 96 97. a 96 :~
~ Mn 0~01 ~.07 0.6 0.09 0.02 0.09
As mg/kg 0.1150 4 95 1- 140 5
Pb mg/kg ~2 7~ 2 72 ~ ~ 79 2~
Sb mg/kg <25<25 <25 <25 <2S <25 100
Cu mg/kg 5524 6 690 4 520 100
Cr mg/kg 855S 7 835 ~5 500 100
Zn mg/kg 6437 600 420 <5 405 loO
5O4Ba mg/k~ <5LG00 <51 O O < 5 9S0 100 .
The de-tailed key corresponding to this table is gi.ven in Table 3.
- 16 -
5~
Table 2
. _ ~ _ __ Exa~ple 4 Example 5 Exa~p~e 6 . .
characteristics max.
e h e h e h concen-
trations
___ _ ~ ._ _
A : shaded off 22.4 2523~0 25 23.3 25
B : coordinate
Y 20.1 20.122.2 22.2 30.3 30.3
X 25.7 26.026.6 26.7 32.7 32.7
Z 17.~ 17.824.3 2g.5 37.5 38.0
_ ._ __ ._ _ ..
C : chromatic
deviation ~C 1.1 0.6 O.S
... _ . ._ . .. _ _
D :tinting 111 100109 100 107 lOC
strength
absorption 9.4 2S 9.0 22 9.5 15
F :brilliancy 76 35 50 29 32 16
G : fineness . .
: in ~
5 min 60 60 80 55 62 37
. - 30 min 22 30 30 27 37 27
H : plI 6.5 5.7 6.2 5.4 7.67.0
I : resistivit~ .
kohm x cm 5.1 7.0 16 10 18 18
.~ . ~_ ~ ~ ............... ~
~ Fe23 97.2 96 97.2 96 97 96
% Mn 0.03 o,oC 0.01 0.1~ 0.04 0.07
As mg/kg l.S 100 2 80 1.8 75 5
Pb mg/kg <2 63 <2 70 ~2 64 20
Sb mg/kg ~25 <25 <25 <25 <25 <2S 100
Cu mg/kg 6 727 5 415 6 354 100
Cr mg/kg <5 869 <S 612 <5 426 100
Zn mg/kg <5 424 <5 395 <5 211 100
BaSO4 my/ky <5 50 <5 1500 <5 3200 100
. . ~ ~ .. _ _ _ . _
The detailed key corresponding to this tabl is given in Table 3
- 17 -
~f~
Table 3
De ~ to ~ables 1 and 2
A ShadincJ rate t ~in ~) to be used with tl~e sample (e) to
obtain the same Y as for the equivalent commercial
pigment with 2S% shading off ~h~
B trichromatic coordinates at t shading ~ for -the sample
(e~ and with 25~ shadiny for i.ts corNmercial e~uivalent
(h)
C chromatic deviation ~C betwean the sample in the example
(e) and its commercial equivalent ~h)
D tinting strength of the sample (e) in comparison ~ith
its commercial equivalent ~h) : TS = 2500/t
E oil absorption tg of oil per 100 y of pigment~
F brilliancy
G crushing fineness in microns.measured after 5 and
30 minutes of crushing in the presence of balls
H pE determined in accordance with AFNOR Standard
T 30-035
I resistivity of the aqueous extract expressed in
kilohms cm
.e characteristics of the pigment described in the exarnple
h characteristics of the commercial pigment with the
closest chromaticity
a maximum concentrations of toxic impurities imposed by
Ministerial Decree of lS October 1964 ~ournal Officiel
date 4 November 1964) relative to substances usable
for coloring foodstuffs
For all the pigments presented in Tables 1 and 2, the
impurities Cd, Hg, Se, Tl U, CrO~2~, Ba2+ and organic
constituents are either undetectable or in a concentration
lower than the miximum limits imposed by the Decree.
- 18 -
