Finished Color Is Spread on Trays and Charged to Vacuum Dryers
GORDON C . INSKEEP
in collaboration with
Associate Editor
A
W. H. KRETLOW William J . Stange Co., Chicago, I l l .
the Bureau of Chemistry, United States Department of Agriculture, for an examination of coloring matter in foods to determine their relation to digestion and health and to establish a guide for their use. It was under this authorization that information was gathered which contributed to the Food and Drug Act of 1906. Calvery (1), in a discussion of the coal tar colors, calls attention to a sizable contribution made by Hesse. Hesse, a coal tar dye expert, was appointed to make the extended study of the dye applications in food products: His complete report was published by the Bureau of Chemistry (7) in 1912. Briefly, the problem was one of selecting the most desirable coal tar dyes for use in foods, There were 80 dyes being offered to the food industry in the United States at that time. By careful study, those which were not deiinitely known t o be harmless were eliminated and a list of seven colors was decided upon. Reds Amaranth Ponceau 3R Erythrosine Orange Orange I Yellow Naphthol Yellow S Blue Indigotine Green Light Green SF Yellowish
N IMPORTANT segment of the tremendous food products industry is that division which produces the “color added” ingredient. There are only a few plants in this country manufacturing food colors. One of the older and well-established firms in the business is the William J. Stange Co..which produces food colors in its Chicago, Ill., plant. It is not just a recent practice to enhance the attractiveness of food products through color addition, although the selection of colors was quite limited prior to the advent of the coal tar dyes. Soon after Perkin’s discovery of the first coal tar dye in 1856, many other syntheKc dyes of a wide range of tints made their appearance. The use nf the new dyes in foods began almost immediately, first in Euro& and then in America. It soon became obvious that some manner of inspection and control of these dye additions to food products was desirable. The complete analysis of many of the dyes was not always known nor were their physiological effects always established. Coal tar colors in foods attained their first legal status in the United States in 1886 when Congress allowed the addition of artificial color to butter. I n June of 1896 Congress took a similar step pertaining to color in cheese, I n 1900 funds were allocated to 12
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 1952
TABLE
r.
COLORS CERTIFIABLE FOR
F.D&C. Designation Blue No. 1 No. 2 Green No. 1 No. 2 No. 3 Orange No. I No. 2 Red No. 1
USE I N FOOD, DRUGS,A N D COSMETICS Color Shade Index No. Greenish-blue iiso Deep blue Bluish-green 666 670 Bluish-green Bluish-green iio Reddish-orange Orange Cherry red 80 Magenta red 184 Bluish-pink 773 Light cherry red .. Reddish-orange 73 Yellow 10 10 Yellowish-orange 61 Yellowish-orange 22 Lemon yellow 840 Yellowish-orange Reddish-violet 697
..
No. 2 No. 3 No. 4
No. 32 Yellow No. 1
No. 2 No. 3 No. 4 No. 5 No. 6 Violet No. 1
0
13
Application Code:
1 = Eggshades = Icings = Pie fillinga
f
4 5 = Candies Beverages (nonalcoholic)
6 = Ice cream
7 = Butter and oleoniarga@e 8 = Sausage casings 9 = Maraschino cherries
COLOR CERTIFICATIONS
colors; 52 of these were approved for internal use and 13 for external use. The certified colors were therefore divided into three The first colors were certified on April 1, 1908. Considerable classes: money had been spent by two manufacturers for equipment and personnel in order to produce colors of certifiable purity. Unfortunately, certification was a t this time on a voluntary basis, and competitors were able to undersell the companies who Pyduced External D&C, for use in externally applied drugs alld costhe certified colors. The government could not bring sujt unless metics only there was evidence of adulteration or misrepresentation. The original list of seven colors soon proved to be inadequate. The prefixes FD&C and D&C, the shade of color produced, and a number designating the various dyes prevents any confusion There was also a demand for oil-soluble colors, buf no such color with technical or uncertified colors containing harmful impurities had been approved. I n 1916 tartrazine was certified, and since then it has largely replaced Naphthol Yellow S. Oil-soluble Yellow and borrowing similar names. The present list of certifiable colors includes 19 FDkC, 68 D&C, and 80 External D&C, or a AB and Yellow OB were approved in 1918. From time to time total of 117. other additions were made, until in 1938 there were 15 The certifiable food colors of these colors. ),600-(FD&C) with their common Under the Food, Drug, and a p p l i c a t i o n s a r e listed in Cosmetic Act of 1938 the use Table I. This list has been 1,500-* of an uncertified color in any a d j u s t e d for several addif o o d , d r u g , or c o s m e t i c tions and d e l e t i o n s s i n c e shipped in interstate comf,400-* 1938. FD&C Violet No. 1, m'erce is absolutely forbidden. the latest addition, was apThe details of the act were proved in 1950 and reported 1,300-* in the Fk-lsral Register (3). worked out during conferences with members of the n The 19 FD&C colors are coal tar dye industry and 1,200.. offered to the market by manufacturers of drugs and lmany organizations. HowW ever, only eight companies cosmetics. By this t i m e about 1500 food color sub1,100.. manufacture the F D & C v) colors: stances (including many mix0 z t u r e s ) were being used. a g 1,000. Through a system of elimination based on duplication of 1. Bates Chemical Co., Lansdowne, Pa. shades, undesirable physio5 BOO2. Calco Chemical Diviv) logical action, essentiality bea sion, Amerioan Cyanamid 0 Corp., Bound Brook N. J. cause of special properties, r 3. Dykem Co., dt. Louis, s t a b i l i t y a n d purity, and Mo. similar properties, the list 4. Hilton-Davis Chemical was finally reduced to 82 coal Co., Division of Sterling tar dyes. Of these 16 had Drug, Inc., Cincinnati, Ohio 5. H. Kohnstamm & Co., previously been approved for Inc., New York, N. Y. me in food. Orange 88 and 6. National Aniline Divit h e p o t a s s i u m s a l t of sion, Allied Chemical & Dye N a p h t h o l Yellow S were Corp., Buffalo, N. Y. 500 7. W a r n e r - J e n k i n s o n added to this Kat. The re1940 il 42 43 . 44 4s 4s 47 40 49 50 51 M a n u f a c t u r i n g Co., St. rnaining dyes were m d e d F I S C A L YEAR Louis, Mo. into two classes and deskFigure 1. FDLC Colors Certified b the Food and Drug 8. William J. Stange Co.. Administration, 194851. (Data &rnlshed by FDA) Chicago, Ill. nated as drug and cosmetic
~ ~ ~ ~ ~ ~ , u , s s h n , ~ ~ ~
Vol. 44, No. 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
14
TABLE11. WATER SOLUBILITY --
OF
CERTIFIED FOODCOLORS5
Temperature,
-
O
F.
__
.
.
~
60 70 80 13.6 Ponceau 3 R 15.1 16.7 17.9 Orange No. 1 2.2 2.7 2.5 3.2 Tartrazine 8.1 10.3 14.9 21.4 17.7 Amaranth 20.9 22.9 26.0 24.0 Guinea Green 30.0 33.2 36.0 Fast Green 24.0 30.0 33.2 36.0 Er throsine 7.4 10.0 8.6 11.4 1.1 digotine 1.5 1.3 1.7 28.0 Siidbet Yellow 30.9 33.7 35 6 5.0 Ponceau SX 7.4 8.6 9.8 Nrrph. Yellow 13.2 14.3 16.0 17.7 will renia!n in solution e'veri a t freezing Light Green will remain in solution c‘ven a t freezing Brilliant Bhie a Chart indirates oiinres of color in 1 gallon of saturated nolutiotl. In dissolving these colors, t h e indicates. Freezing
40
50
Production of certified food colors in the United States since 1940 is shown graphically by Figure 1. Certification records prior to this time would not be indicative of the industry-wide production rate because of the voluntary nature of the certification procedure. CHARACTERISTICS O F CERTIFIED FOOD C O M R S
The certified food colors exist in several different forms. The term straight color or primary color is used to designate a color included in the official FD&C list. All the straight colors are in powder form, to be dissolved by the user as needed or used in the preparation of stock color solutions or pastes. The straight colors are as nearly pure coal tar dye as the production technique nil1 allow. The strength runs from 86 to 94% pure dye, for water-soluble colors, and not less than 99% pure dye for the oil-soluble colors. The balance is primarily moisture and sodium chloride. In preparing lakes from certified colors, the dye may be precipitated with the sodium, potassium, aluminum, calcium, strontium, or zirconium ions. Suitable substrata are aluminum, blanc fixe, gloss white, clay, titanium oxide, zinc oxide, talc, rosin, aluminum benzoate, or combinations of these. Lakes have a rather extensive use in the cosmetic industry, but in so far as food is concerned they are authorized only for coloring shell eggs (Easter eggs). The only lakes permitted for this purpose are those made by extending on a substratum of alumina a salt prepared froni m e of the water-soluble FD&C colors by conibining such color with aluminum or calcium. In this application the color is removed with the shell and does not become a coniponent of the food on which it is used. hIixtures, also known as blends or secondary shades, are coniposed of two or more certified colors without any diluent or R color made from one or more certified colors mixed with a har.11less ingredient such as salt or sugar. Mixtures containing no diluents are often referred to as “basic strength.” I n any case, to comply with regulations, the pure dye strength must be stated on the product label. Paste colors are mechanical mixtures of the dry color in suc~li diluents as glycerol or glycerol and water with powdered sugar added as a thickening agent. The paste colors are specifically designed for use in hard candies or in products where a further addition of water i s undesirable. Solutions of certified colors may be purchased directly froni ii manufacturer, but from an economic standpoint it is better to buy the powder and prepare the solution as needed. Solubility. Of the 19 certified food colors, 15 are soluble in water. Evenson and Forrest (9)published one of the early studies on dye solubility. They made special efforts to eliminate the effect of impurities. Most of the dyes which they used were purified by several recrystallizations from aqueous alcoholic solution. In a discuseion of the application of certified food colors, Kretlow (9)published the water solubility a t various tempcratures of
90 19 1 4.0 35.3 28 2 38.4 38.4 12.8 1.9 37.4 10.4 20 3
100 20.3 5.0 41.5 30.4 42.2 42.2 14.4 2.1 39.2 11.0 23.0
solution must be heated
I10 21.6 8.6 45.9 31.9 46.0 46.0 16.0 2.3 40.9 11.5 26 0 at. least
120 22.5 13.2 48.8 33.6 48.6 48.6 17.6 2.5 42.6 11.8 29.5
~
_
130 22.8 17.5 49.9 35.3 51.2 51.2 19.3 2.8 43.8 12.1 32.8
50” higher than the chart
a number of the food colors. The data are summarized in Table 11. The solubility properties were also outlined in extensive tabulations published by Peacock (11). All but one of the water-soluble colors exist as sodium salts. The exception is FD&C Yellow No. 2, the potassium salt of Naphthol Yellow S, which is relatively insoluble as compared with the sodium salt. From an application standpoint, all the water-soluble colors are “acid dyes,” and with the exception of erythrosine, all are sulfonates. Erythrosine obtains its acidic character from a carboxyl group The four colors, FD&C Red No. 32, FD&C Yellow No. 3, FD&C Yellow No. 4, and FD&C Orange No. 2 are soluble in oils and insoluble in water, largely because they lack salt-forming radicals. The amount of sodium chloride in the dry colors affects the solubility decidedly. When blends containing salt as a diluent are put in solution, there is a marked decrease in the solubility in the combined colors. The addition of salt in sufficient quantity to most solutions of water-soluble colors will cause precipitation of the dye. Alcohol, a conimon preservative in solutions containing erythrosine, has a decided effect on the solubility of some colors. A comparison of the solubility of a few of the straight colors in 10% alcohol with solubility indistilled water is shown in TableIII. ~~
~~
~
AQUEOIJS A N D ALCOHOLIC 111. COMPARATIVE SOLUBILITIES OF COMMON CERTIFIED FOODCOLORS
*ABLE
Ounces of Color/Gallon a t 70” F. Distilled water, oz. 10% Alcohol, 16.7 10.0 22.9 12.8 10.0 10.0 8.6 6.0 33.2 25.6 33.2 25.6 1.5 1.6 14.9 12.8 33.7 20.0 2.7 2.7
.
I’oticeau 31t .4niaran t h ICrythrosinr Ponceau SI; Guinea Green Fast Green Indigotine Tartraaine Sunset Yellon Orange No. 1
07.
The four “oil-soluble” dyes dissolve in aromatic hydrocarbons and to some extent in the aliphatic hydrocarbons. They are soluble in chloroform and most other halogenated solvents (10). Chemical Properties. The specific properties of a dye, such as fastness and chemical behavior, depend largely on the substituent groups. These groups are of two kinds:’ the chromophoric groups such as azo and nitro and the auxochromic or saltforming groups, such as the acidic or hydroxyl groups. The chromophoric groups determine the chemical class to which the dye belongs and its reaction to oxidation or reduction. The auxochromic groups are largely responsible for the dying properties and the action toward acids, alkalies, and light. Froma chemical standpoint, the certified FD&C colors fall into Rix classes:
_
INDUSTRIAL AND ENGINEERING CHEMISTRY
16
Nitro Indigoid Xanthene
Azo
Triphenylmethane Pyrazolone
In most artificially colored foods an actual chemical dyeing does not take place, but the material merely becomes stained by a mechanical combination with or absorption of a colored substance as in beverages and candy. In some applications, however, dyeing does take place. This is true in the coloring of sausage casings, where there is an actual affinity between the dye and the animal tissue which is probably due to a combination between the amino group of a protein molecule with the sulfonic or acid group of the dye. Changes in dyes consisting either in complete or partial loss, or an alteration of color, may occur for several reasons. Some of the more common causes for the color change are exposure to light, action of oxidizing or reducing agents, and the action of acids or alkalies. The relative stabilities of the FD&C colors are summarized in Table IV. STABILITIES* O F FD&C COLORS TABLE1V. RELATIVE FD&C Color Blue No. 1 No. 2 Green No. 1 No. 2 No. 3 Orange No. 1 No. 2
Sanlight F P
Oxidation P P
F
F P
F
Attack Reduction P F
P P
Acid G P
F
I
Alkaline I? P
P I
No. 3
Violet No. 1 a Code of stability: ble.
F C; =
P
good; F
= fair;
P P E‘ P = poor; and 1 = insolu-
The degree of fastness of various coal tar colors may vary with the dye itself, the cltture and intensity of light, the amount of moisture present, and the medium in which the color is used. From a light fastness standpoint, the best FD&C colors are Red No. 1 and Red No. 4. Orange No. 1 has only limited fastness, and Blue No. 2 is extremely sensitive to light. A common property of dyestuffs is their ability to take up hydrogen with the formation of colorless compounds. I n nitro and azo dyes, amino compounds are produced, whereas other classes are converted into so-called leucc-compounds which contain two more atoms of hydrogen than the original dye from which they are derived. They are reconverted into the original dye on oxidation. Indigoid dyes, on reduction, give rise to leucc-compounds which are readily reoxidized by air. Most of the certified food colors are very unstable in the presence of reducing agents. The same is true in the presence of oxidizing agents, although the red colors are slightly more stable than the others. The most common type of reduction encountered in the use of food colors involves the action of a metal such as tin or iron in an acid medium. The acid acts on the metal liberating the hydrogen which in turn reacts with the color to bring about a reduction. The result is a loss of color. This reaction is utilized in the quantitative estimation of many dyes and all the certified food colors with the exception of erythrosine. The dyes are titrated with standard titanium trichloride solution according to official A.O.A.C. methods. The procedure is outlined in detail in a government publication (6). The certified food colorR vary considerably in their action
Vol. 44, No. 1
toward acids and alkalies. Indigotine, for example, fades rapidly in an acid medium; erythrosine is completely precipitated and should not be used in any product where acid is present. The azo dyes are comparatively stable in weak acids, but some of them, especially Orange No. 1,should not be used in an alkaline medium. Spectral Properties. Coloring agents operate within the “visible range” of 400-to 700-fiwave length. By plotting light transmittance or absorbancy measurements against wave length, identifying curves can be obtained for each of the water-soluble colors. The technique is described in some detail by Steams (18). At the present time the technology is not sufficiently advanced to make i t practical for all companies to market coloring agents to meet exact spectral requirements. However, for reference purposes, Peacock (11) has presented transmittance curves of the more important water-soluble certified dyes. Under standardized conditions, these curves maintain their shapes regardless of concentration; the only change is a vertical (transmittance) displacement. Specifications. The food color industry is now under stringent government control and supervision matched only in the manufacture of antibiotics. Standards and specifications are set forth under which the approved colors must be manufactured and sold (4). Herrick (6) has discussed the regulations pertaining to the coal tar colors in some detail. For example, the maximum tolerable amount of the following may b,e specified: volatile matter; insoluble matter; ether extractives; chlorides. and sulfates of sodium; mixed oxides; subsidiary dyes; uncombined intermediates, and lead and arsenic. A minimum tolerance is also placed on the pure dye content. This limit is not the same for all certified colors; in each case the purity required is such that manufacturing technique must be carefully controlled. The methods of analysis applicable to the certifiable coal tar colors have also been published by the Food and Drug Administration (6). A few of the specifications applicable to Orange No. 1, as an example, are summarized in Table V. Each manufacturer must submit a uniform representative sample of each batch of color offere! for sale. If the sample submitted is found to meet specifications a lot number is assigned under which that particular batch of color must be sold. These certification numbers are then keyed to the plant batch numbers, and the completed record with a record of the final customers is retained for one year.
TABLE V.
SPECIFICATIONS ( 5 ) FOR FD&C ORANGE No. 1 Maximum Allowed, %
Volatile matter (at 135O C.) Water insoluble Ether extracts a-Naphthol Chlorides and Hulfates of sodinm Mixed oxides Orange I1 Lead Arsenic (as AsaOa) Heavy metals (except Pb and As) Pure dye
10 0 0.3 0 2 0 1 4 0 1 0
5 0
0 001 0 00014
Trace Not less than 85 0%
The certification of colors prior to the passage of the Food, Drug, and Cosmetic Act of 1938 was a public service and without charge. Under the new act, however, the color certification section of the administration became self-sustaining through fees charged for all services connected with the certification. I n 1940,the Food and Drug Administration was transferred from the Department of Agriculture to the Federal Security Agency and is under the supervision of a commissioner of food and drugs. The United States is the only country that has approved a complete list of dyes and specifications far drugs and cosmetics as well as foods. There are still a few foreign countries that do not regii-
January 1952
Figure 2.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Flow Sbwt for the Production of FD&C Orange No. 1 at Chieago, Ill., Ptant of W. J. Stange Cn.
17
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
18
late the use of dyes even in foods. Products containing coal tar dyes which are imported for sale as food, drugs, or cosmebics must contain only colors certified in this country. CHEMISTRY OF ORANGE NO. 1 PRODUCTJON
The preparation of FD&C Orange No. 1 illustrates well the reactions involved in preparing a Certified food color of the azo type. psulfanilic acid and soda ash react to form the soluble sodium salt with the evolution of carbon dioxide gas. NHz
fi v
+ Na2C03-+
2
2
Diazotization
p-Sulfanilic acid In order to obtain sulfanilic acid in a finely divided and highly reactive form, the sodium salt then reacts with an excess of hydrochloric acid.
8' 6 SOaNa
+ NaCl
+
but it is of interest to mention briefly their methods of manufacture. Each is basically a coal tar derivative. To prepare sulfanilic acid, benzene from the first fraction of the coal tar distillation is nitrated to form nitrobenzene. The nitrobenzene is then reduced to form aniline and subsequently sulfonated to yield the sulfanilic acid. The a-naphthol is obtained from coal tar naphthalene. Nitration of the naphthalene gives a-nitronaphthalene and subsequent reduction yields a-naphthylamine. By heating the a-naphthylamine with concentrated sulfuric acid in the presence of water the amino group is replaced by the hydroxyl to form the desired anaphthol.
+HzO+COz
S08Na
+HCl
Vol. 44, No, 1
803H
The sulfanilic acid is diazotized by adding sodium nitrite to the acid solution. The temperature of this reaction is held below 5' C . because of the instability of the diazonium compounds.
NEN-
A1
v S03H Diazosulfanilic acid The sodium nitrite in acid solution gives the active diazotizaIn the meantime the sodium salt of a-naphtion agent, "02. tho1 is formed in another vessel by mixing a-naphthol with sodium hydroxide.
a-Naphthol A coupling of this sodium salt with the diazosulfanilic acid brings about the formation of the dye.
NaOsSDN=NC-)OH
n
Orange No. 1
W
PRODUCTION OF ORANGE NO. 1 IN CHICAGO PLANT OF WILLIAM 3. STANGE CO.
Illustrative of the general procedure for making certified food colors in the William J. Stange plant is the production of FD&C Orange No. 1. This is a batch operation as indicated by the flow sheet, Figure2 Raw Materials
The raw materials for producing Orange No. 1 are psulfanilic acid and a-naphthol. Neither of these :Ismade by the Stange Co.,
The diazotization of the sulfanilic acid is carried out in a 1OOOgallon tank constructed of resin-impregnated asbestos ( 4 8 ) and equipped with a top-entering agitator. Two hundred gallons of water are charged to the tank and heating is begun by sparging live steam a t the bottom of the tank near the periphery. Steam enters the tank through a 1.5-inch resin-impregnated graphite ( 7 E ) line with ejector head. The water is heated to boiling. While the tank contents are being agitated and heated, 275 pounds of sulfanilic acid and 100 pounds of soda ash are charged manually to the tank. The heating and agitating is continued for approximately 1 hour during which period any free aniline is driven off and exhausted to the atmosphere through the fume system. After the dissolution process the tank contents are allowed to stand overnight. In a 60-gallon stainless steel tank located directly over the diazo tank, 100 pounds of sodium nitrite are mixed with approximately 30 gallons of water. Mixing is done by hand, using a wooden paddle. The contents of this tank are also held overnight. I n a 5Wgallon stainless steel tank provided with agitation, 204 pounds of a-naphthol and 57 pounds of sodium hydroxide are dissolved in 340 gallons of water. The a-naphthol solution is also heated by introducing live steam through an open-end pipe for a period of approximately 1 hour and then held overnight. The first procedure each morning in the Stange plant is the icing operation. Ice in 200-pound blocks is delivered to the plant by truck. The blocks are taken to the third floor by elevator and wheeled by twc-wheel cart to a portable ice-crusher (6E). The crusher is powered by a 5-hp. electric motor. The ice is chipped manually and fed into the crusher hopper. A rotating drum with attached pointed prongs breaks the ice down to nearly snowlike form. This falls into the intake of the ice pump (or slinger) which is driven by the same motor and is an integral part of the crusher. The snow is propelled through an 8inch flexible hose into the desired tank. Fourteen hundred pounds of ice are used in the diazotization, and 2000 pounds of ice are charged into the coupling tank. The coupling tank is a 2000-gallon stainless steel tank equipped with topentering agitator. Just prior to icing the diazo tank, the anaphthol solution is dropped by gravity flow into the coupling tank. Neither the diazo nor the coupling tanks are insulated or provided with cooling coils. From carboys, 400 pounds of 18" I36. hydrochloric acid is charged to the diazo tank. This is a manual operation. Rubber buckets are used for the transfer. The sodium nitrite solution is now dropped into the diazo tank. The diazo tank is now ready for checking by the chief chemist. The amount of sodium nitrite is purposely calculated short of the theoretical requirement, and it is the bsk of the supervisor to make the final addition. I t is much easier to add the additional nitrite than to correct for too great an excess. Potassium iodide starch indicator paper is used to tell when an excess of nitrite is present. The chemist adds sodium nitrite from a metal scoop until the test paper shows a slight excess. He also tests for proper acidity using Congo red test paper. The pH of
January 1952 '
IN D U S T R I A L A N D E N G IN E E R-I-N G C H E M I S T R Y
the diazotized sulfanilic acid runs from 3.5 to 4.0. When approved by the chemist, the coupling reaction is begun. Temperature of the diazo tank by this time is approximately 5" C. Coupling
The diazotized sulfanilic acid is added by gravity fibw to the coupling tank containing the a-naphthol and ice. The addition is controlled manually and generally takes about 15 minutes. The temperature in the coupling tank seldom rises above 10" C. The addition is stopped when there are 30 or 4 0 gallons of the diazotized acid left in the tank. A spot test on filter paper is then made, using R-salt solution. R-salt is a derivative of &naphthol having the chemical structure
The color agglomerates near the center of the filter paper spot and the liquid spreads in a colorless circle around it. If there is an excess of the diazo compound, the R s a l t solution will form an orange dye when i t contacts this outer circle. Small additions of the diazo solution are made until this color reaction on the filter paper is obtained. The color is completely "salted out" (common ion effect) by addition of sodium chloride; 400 pounds are added manually from 100-pound paper bags. At this time water wash from the previous day's final filtration is added to the coupling tank. The wash water is held in a 500gallon stainless steel tank situated in such a manner that the addition can be made by gravity flow. The color slurry is again checked with the R-salt solution. Usually another slight addition of the diazo solution is required. The chemist makes these checks because of the critical importance of having an excess of the diazo solution. The final product must contain no unreacted a-naphthol. The coupled slurry is then dropped to a 36-inch filter prem ( I 1 E ) located on the second floor. The press is provided with 54 wooden plates and frames. Filtration is by gravity flow for the first 30 minutes but is completed using a centrifugal pump (1E) having a phosphor-bronze impeller. A normal batch can be filtered in 1.5 to 2 hours. The filtrate contains very little recoverable color and is discharged to the sewer. The press is blown dry, using air from a twin c~lindercompressor (SE). The press is usually blown for 1 hour. Purification
A 2000-gallon stiainless steel dissolving tank equipped with agitator is charged with 800 gallons of water. The water is heated to 55" C. by sparging live steam into the bottom of the tank. The filter cake from the crude press is then shoveled into the dissolving tank. To facilitate filtration, 15 pounds of filter aid ( 6 E ) are added. Sufficient cold water is then run in to cool the tank to 42' C. The volume of water required varies with the room temperature. At 42' C. the desired Orange KO.1 is still soluble and filtration results in no loss of color. The dissolved crude is pumped through a stainless steel leaf filter ( 8 E )which has been previouely precoated with 25 pounds of filter aid (6E). The filtered crude solution is then collected in a 2000-gallon stainless steel salting-out tank. Three hundred and fifty pounds of sodium chloride are slo~vlyadded to the solution with a g i t a tion. The tank contents are then held overnight. The leaf filter, which retains any insoluble impurities, is cleaned merely by backwashirig to the sewer. The salted-out orange is filtered through a finished filter press of design identical with the rrude press. The salting-out tank is
19
located on the third floor and the finished press on the first floor; therefore, gravity feed is possible. The press is blown dry with air. Both the filtrate and the press blowings are discharged to the sewer. The prew cake is then washed with two 175-gallon batches of water. The wash water volume is measured in a 5Wgallon wooden tank located on the second floor. Since Orange No. 1 is water soluble to a certain extent, it has been found advisable to recycle the wash water to the coupling tank. It is collected and held in a make-up tank prior to addition to the coupling tank. Drying and Blending
The filter cake from the finished press is placed on trays and charged to a.steam heated dryer ( I I E ) . Moisture content of the press cake runs about 65%. The dryer is supplied with a vacuum pump and is normally operated a t a vacuum of 26 inches of mercury. The steam pressure to the dryer heating coils is approximately 50 pounds per square inch gage, giving an operating temperature of around 300" F. The crude is dried overnight and is ground in a rotating-hammer pulverizer (9E). The pulverized product is held in 55gallon coated drums until laboratory analysis has been made. In spite of many points of possible mechanical loss in the process, the over-all yield is surprisingly good. Normal batches frequently are produced with over 807, yield based on a-naphthol. After several batches have been accumulated and have satisfactorily passed laboratory snecifications they are blended in a barrel-type blender and the blended color is held in 55-gallon coated drums. Both the pulverizer and the blender are charged using electrically powered barrel dumpers @E). Samples of the blended color are sent to the Food and Drug Administration in Washington, D. C., for analysis. If the blend is certified a lot number is assigned and the product is ready for shipment. Equipment Cleanup
Although the Stange plant ordinarily produces four or more different colors simultaneously, several of the colors are made in the same equipment. Fortunately, the demand for Orange No. 1 warrants continuous production ,of this color. The equipment used for making Orange No. 1, with the evception of the grinding and blending equipment, is therefore used only for Orange No. 1 production. The various reaction vessels are rinsed with cold water after the completion of each batch. The leaf filter is backwashed to the sewer after each run; the filter is dismantled and the filter bags removed and cleaned every 2 or 3 days, depending on the performance of the filter. The pulverizer is constructed in such a manner that it may be dismantled easily for cleaning. Obviously, when changing from one color to another, a thorough cleanup of the pulverizer and the blender is required. Since the color^ are water soluble, the cleanup is easily accomplished by using a water hose. The trays used in the vacuum dryer are thoroughly cleaned with a water hose after each batch. Personnel and Working Schedule
There are 18 production employees in the color division of the Stange plant. They are supervised by an operations foreman. The chief chemist has two assistants working in the color laboratory. The division is under the supervision of a divisional director of production and research. There are four maintenance employees assigned to the color division and the spice extraction unit which is located in an adjacent building. These employees, under the direction of the plant engineer, take care of all routine maintenance and repair.
20
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
This is primarily pipe fitting, pump packing, and routine lubricating. At the present time, the color division is operating with one shift per day, 5’/0 days per week. The average daily working shift is 9 hours; employees draw pay at time-and-one-half rate for time over 40 hours per week. The actual shutdown time each day varies, depending on filtration nates and the mechanical performance of other equipment. All operations are 80 designed that they may be interrupted a t several points by extended holding periods without loss. In many cases, these holding periods would be required even if the plant were operating on a 24hour basis. Without additional tank capacity it would be impossible for Stange to operate on a continuous schedule. Fume and Dust Control
The Stange Co. has just completed an extensive renovation program, involving the expenditure of $lOO,OOO. Much of the renovation effort was directed toward improving the working conditions in the color division. Each of the reaction vessels is now covered and provision has been made for exhausting steam or other vapors formed in the reaction. In the equipment for Orange No. 1, the diazo tank, the coupling tank, and the dissolving tank are fitted with &inch vents which discharge into a ceiling header leading to the roof. All fume exhaust duct work leads to the roof where a 7500 cubic feet per minute centrifugal blower driven by a 3-hp. electric motor discharges to the atmosphere. The duct work is galvanized iron. The exhaust system has beeh quite successful. Steam in the operating rooms has been eliminated as well as objectionable or irritating odors. Condensation on water pipes and ceiling members has also been eliminated. The pulverizing and blending operations have been isolated in an enclosed room. Dust from the pulverizer is collected in a multiwash dust collector (IOE)(located on the roof). The grinding room is designed so that it can easily be washed down with a water hose. Materials of Construction
Materials of construction in a plant producing certified food colors must be chosen with extreme care. More important than the corrosion of the equipment itself is the possibility of contamination of the final product. Colors which come io contact with metals such as iron, tin, zinc, and aluminum may be reduced. Copper has no reducing effect, but does alter the shade of some colors. Glaas or glass-lined equipment, although *expensive, would be considered ideal. The large vessels used in the production of Orange No. 1 are constructed of Type 304 stainless steel. Seams and walls were carefully made of the same materials to avoid a possible cathodic reaction. A diazo tank of wooden construction was used for a number of years but has recently been replaced by a tank constructed of impervious resin-impregnated asbestos ( 4 E ) . The tank has not been in operation long enough to completely evaluate this material of construction, but preliminary indications point to good results. The wooden plates and frames used in the filter press have been completely satisfactory. However, as is true of any wooden equipment, the presses must not be allowed to dry out. They are
Vol. 44, No. 1
always filled with water when they are not to be used for any period of time. FUTURE PROSPECTS
It is reasonable t o predict that there will not be many new colors added to the list of certified food colors. Prior to the enactment of the present Food, Drug, and Cosmetic Act, a color could not be certified unless it was freely available for manufacture by anyone who wished to do so. Although under the new act this policy has been modified to permit certification of patented colors, so far no patented color has been added to the FD&C list. Although some research is being carried out on process improvement, no radical changes can be expected. It takes a substantial cost reduction or quality improvement to justify any major change in the established method of producing the food colors. It is safe to assume that the food color industry will continue to grow. The production of food and interrelated products is directly related to the growth or decline in population. There seems to be no decline in population in sight. LITERATURE CITED
(1) Calvery, Herbert O.,Am. J. Pharm. 114, 324-49 (September 1942). (2) Evenson, 0. L., and Forrest, S. S., Am. DyestuffReptr., 26, No.6, 117 (1937). (3) Federal Register, Washington, D. C., 15 F.R., 3517 (June 7, 1950). (4) Federal Security Agency, Washington 25, D. C., “Coal-Tar Regulations,” September 1940. (0) Zbid., “Methods of Analysis Applicable to Certifiable Coal-Tar Colors,” May 1949. (6)Herrick, A. D.,“Food Regulation and Compliance,” pp. 9851040,New York, Revere Publishing Co., 1947. (7) Hesse, Bernard C., U. S. Dept. Agriculture, Bureau of Chemistry, BUZZ. 147 (February 1912). (8) Joyce, A. W., “Synthetic Dyestuffs,” Allen’s Commer. Anal., 6th ed., Vol. 6,Philadelphia, P. Blakiston’s Son & Co., 1928. FoodZnd., 12, No. 5,38-40 (May 1940). (9) Kretlow, W. H., (10) Kretlow, W. H., Nutl. Bottlers’ Gaz., 62 (March 1944). f11) Peacock, William €I., American Cyanamid Co., Calco Chemical Division, Tech. Bull. 715 (1944). (12) Rowe, F. M., “Colour Index,” SOC.of Dyers and Colourists, Yorbhire, England, Bradford, 1924. (13) Stoarns, E. I., Am. Dyestufl Reptr., 33, 1 (1944). Processing Equipment
(1E)Aurora Pump Co., Aurora, Ill., centrifugal pump, Type GGU. (2E) Colson Equipment & Supply Co.. Los Angelea, Calif., barrel dumper, Model 4001. (3E) Gardner Denver Co., Quincy, Ill., twin cylinder air compressor.
(4E)Haveg Corp., West Newark, Del., corrosion-resistant equipment. (5E)Johns-Manville Co., New York 16, N. Y., Hyflo Super-Cel. (6E)Link-Belt Co.,Chicago 1, Ill., portable ice cruaher. (7E) National Carbon Co., Inc., Cleveland, Ohio, Karbate equipment. (8E)Niagara Filter Corp., Buffalo, N. Y., filter, Model 36-20, (9E)Pulveriaing Machinery Co., Summit, N. J., Mikro-Pulveriier. (10E) Schneible, Claude B.,Co.. Detroit, Mich., Multi-Wash eollector, Type HC. (11E) Sperry, D.R.,& Co., Batavia, Ill., filter press, Type 37. (12E) Stokes, E. J., Machinery Co., Philadelphia 20, Pa., vaauurn dryer.
R E C ~ X VNovember BD 15, 1951
