Identification of Sulfonated Azo-2-naphthol Dyes ROBERT F. MILLIGAN, SAMUEL ZUCKERMAN, AND LOUIS KOCH H. Kohnstamm Research Laboratories, Brooklyn, N. Y. A rapid and simple method has been developed for the identification OF sulfonated azo-%naphthol dyer by catalytic reduction of the azo bond, and the separation OF the scission products with ethanol. Equivalent weight determination of the aminosulfonic acid and its conversion to the S-benzyl isothiourea derivative enable the analyst to differentiate between isomeric compounds. The method is not applicable to mixtures.
THE
identification of the reduction products from sulfonated azo dyes usually presents many difficulties to the dyestuff chemist that are not encountered in the analysis of the analogous unsulfonated compounds. As shown in a previous paper (8), the differential solubility of the amines, diamines, and amino-2naphthol in immiscible solvents can be used to effect their separation. The same procedure, however, is not applicable to the reduction products of the sulfonated azo-2-naphthol colors because it necessitates the introduction of a buffer salt which interferes with the isolation of the pure sulfonic acid. Many analytical methods have been proposed for the characterization of aromatic sulfonated amines, and the literature on this subject has been thoroughly and excellently reviewed by Chambers and Watt (d) and Chen and Cross (3). The latter authors pointed out the complications involved in this type of analysis, and suggested the formation of the stable arylamine salts of the sulfonic acids as a means of identifying these compounds. The method involves the protective acetylation of the amino group, as a necessary preliminary to the formation of the
Table
Diazotized Aryl Aminmulfonic Acid
1.
Identification of Sulfonated Azo-2-naphthol D y n M.P. of Bensyl Isothiourea Yield ,of Derivative Molecular Weight Calcd. Found
173.1 Sulfanilic acid 173.1 Metanilic acid 187.1 2-Aminotoluene-5-sulfonic acid 187.1 4-Aminotoluene-2-sulfonic acid 187.1 4-Aminotoluene-3-sulfonic acid 201.2 4-Amino-m-xylene-6-aulfonic acid 207.5 3-Cliloro-4-aminobenzene sulfonic acid 207.5 2-Amino-4-chlorobenaene sulfonic acid 207.5 2-Amino-5-chlorobenzene sulfonic acid 221.5 3-Amino-6-chlorotoluene-4-aulfonio acid (Red Lake C base) 221.5 11. 2-Chloro-4-aminotoluene-5-aulfonicacid (2 B acid) 12. 1-Aminonaphthalene-6-sulfonic acid 223.1 (Cleve's acid 1-6) 13. 1-Aminonaphthalene-7-eulfonic acid 223.1 (Cleve's acid 1-7) 223.1 14. 2-Aniinonaphthalene-1-sulfonic acid (Tobiaa acid) 223.1 15. 1-Aminonaphthalene-4-sulfonic acid (naphthionic acid) 223.1 16. 1-Aminonaphthalene-5-suIfonic acid (Laurent s acid) 223.1 17. 2-Aminonaohthalene-6-sulfonic acid (Broenneb acid) 223.1 18. 1-Aminonaohthalene-8-aulfonic acid' (Peri acid) 19. 4-Amino-2,5-dichloroaniline-4-sulfonicacid 242.0 20. 2-Aminobenzene-1,4-diaulfonic acid 253.1 21. l-Arninonaphthalene-4,8-disulfonicacid 303.2 (disulfonic acid S) 22. 2-.4minoiiaohthalene-3.6-disu~fonic acid 303.2 (Amino R acid) 23. 2-Amino~iaphthalene-48-disulfonic acid 303.2 24. 2-Aminonaphthalene-6:8-disulfonicacid 303.2 (amino G acid)% Halogen content. 0 Chambers and Watt (8) report presence of 20 moles of water. Hennion and Schrnidle (7). d Purified samole showed Dresence of 1 mole of water. on titrating 0.1 H sodium hyaroxide. . e Benzoyl derivative of amino-2-naphthol not isolated. I Isolated as acid bariuni salt, wiih 1 mole of water. 1.
2. 3. 4. 5. 6. 7. 8. 9. 10.
arylamine salt, and it does not include certain naphthylamine disulfonic acids which are of importance to the color chemist because of their use in the manufacture of certain commercial dyes. Of the proposed procedures, only one, the formation of the S-benzylthiouronium salts of the sulfonated amines, showed evidence of being rapid in execution and simple in application (I,$,5, 6,9). These derivatives are crystalline and have melting points which enable the analyst, in most cases, to differentiate between isomeric aminosulfonic acids. Where the melting points of the isomeric compounds are close to each other, the determination of the equivalent weight is a deciding factor, because of the presence of molecularly combined water (see footnotes to Table I). I n all analyses the equivalent weight was found to be identical with the molecular weight. The aminosulfonic acid, isolated from the reduction reaction, is purified by crystallization from water, and the establishment of the equivalent weight by titration with 0.1 N sodium hydroxide provides both an indication as to the identity of the acid and a convenient source for the formation of the desired derivative. As in previous work (8),the hydrogenation spparatus of Cheronis and Koeck (4) was utilized for the reduction. The scission products of the sulfonated azo-2-naphthol dyes were separated from each other by means of the differential solubility of the aromatic aminosulfonic acid and the amino-%naphthol in ethanol, the former being relatively insoluble. Technical grades of aromatic aminosulfonic acids were used to synthesize the dyes, and the purification of the colors was not found to be necessary.
170.5 173.3 190.5 188.0
188.2 201.0 209,3 211.0 211.5 217.3
Cr stalhzed SulLnic Acid Gram 0.242 0.134 0.064 0.260 0.261 0.174 0.081 0.100 0.100 0.245
Observed (Uncorr.)
Literature
c.
* c.
184-5 147-8 190-1 153-4 168-9 152-3 191-2 195-6 180-1 171-2
187-8
Sulfur Content of Bensyl Isothiourea Derivative Calod. Found
%
%
....
....
.... .... .... .
I
.
.
....
9 49' 16.51
9.98C 16.80
217.5
0.120
163-4
9.15'
223.4
0.132
190-1
16.44
16.55
9,100
224.2
0.194
163-4
16.44
16.49
223.3
0.178
138-9
....
16.44
16.68
224.0
0,356
96-7
195.1b, 103-4c
16 44
15.90
223.5
0.247
182-3
179.4
16.44
16.52
233,2d
0.278
182-3
....
16.44
16.53
237.5d
0.048
150-2
300 (dec.) b
16.44
16 45
246.5 337.5J 312.2h
0.090 0.272 0.130
181-2 176-7 213-4
17.37' 21.870 20.14@
17.64O 22.060
393 . O f
0.314
202-3
888.61
0.396 0.201
226-7 oil
368.5k
@
.... I
.
.
.
....
209-11 (dec.)r 276 (dec.)l
20.40@
20.14~
20. 06@
20.140 20.14s
20.420
...
Calculated as double benzyl isothiourea derivative.
h If barium aalt of dye is used, acid barium salt will be isolated.
Eroesaive decomposition of amino-2-naphthol occurred, and no benzoyb derivative isolated. 8 Chambers and Watt (8) report presence of 1 mole of water. L Isolated as acid barium aalt. I Chambers and Watt (8) report presence of 8 moles of water. i
with
I N 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
570
GENERAL PROCEDURE
Vol. 17, No. 9
0.1 N sodium hydroxide to determine its equivalent weight,
PREPARATION OF REDUCTION PRODUCTS. Freshly F u n d Adams-Voorheea platinum oxide (0.05 gram) is placed in the Cheronis hydrogenating unit, and the catalyst is suspended in 20 ml. of distilled water. Hydrogen as a t atmospheric pressure, preferably from a tank, is bubbled though the suspension for 2 to 5 minutes, in order to convert the platinum oxide to colloidalplatinum blmk. Then 1 gram of dye, 10 ml. of concentrated hydrochloric acid, and 30 ml. of isopropyl alcohol are added t o the platinum black suspension, the hydro enatin unit is heated by immersion in hot water to 80" to 90' and fydrogen gas is passed through the mixture at such a rate that contihuous agitation is maintained. The end of the reduction is indicated by decolorization of the dye solution. SEPARATION OF REDUCTION PRODUCTS. The isopropyl alcoholwater mixture of the scission products is transferred to an e v a p orating dish 0.25 ml. of a stannous chloride solution containin 100 grams oi stannous chloride in concentrated hydrochloric aci; per 100 ml. of solution is added to prevent excessive decomposition of the amino-%naphthol and the mixture,is evaporated to dryneas on the steam bath. "he dried residue is triturated with 25 ml. of 95% ethanol for about 1 mmute, filtered, and washed with 10 ml. more of the solvent. Then 0.25 ml. of the stannous chloride solution is added to the filtrate containing the amino-%naphthol, the ethanol is removed by eva oration, and 5 ml. of benzoyl chloride and 200 ml. o! a 5% so&um h droxide solution are added t o convert the amino derivative of &e couplin component to the dibenzoyl compound. Crystallization from 9 5 6 ethanol gives a product that has a melting oint of 232-3' C. The ai)cohol-insoluble aminosulfonic acid is crystallized from water that haa been acidified with 5 ml. of 6.N hydrochloric acid, and to which has been added a small quantity of Norite. After filtration, the solution is concentrated t o a very small volume and chilled in the refrigerator usually overnight. The precipitate is collected washed with a few milhlitors of 95% ethanol, and dried 8t llo'.~. A weighed quantity of the acid is dissolyed in 100 to 200 ml.. of water, heated if necessary to effect solution, and titrated with
d,
using phenolphthalein as the indicator. (Acids that do not dissolve in water titrate with no detectable decrease in accuracy.) The sodium salt of the sulfonic acid is concentrated to 4 to 10 ml., depending upon the original quantity of acid and is cooled and added to 1.5 times its weight of S-benzyl \sothiourea hydrochloride, dissolved in 2 to 5 ml. of water. The derivative usually precipitates out immediately or, if not, does so on stirring. If an oil results standin overnight causes solidification of all but one of the aci& studiej, One crystallization from a minimum quantity of water, usin decolorizing Norite, usually yields the correct melting point of d e aminosulfonic acid derivative. Occasionally, the presence of excessive inorganic adulterant in the ori 'nal dye will result in an exceptionally small crop of the purifiefaminosulfonic acid. When such is the case, the analyst can start with a lar er color sample or, when an additional sample is not available, t f e mother liquor containin residual aminosulfonic acid can be evaporated to dryness. %ulfonic acid can be converted to the S-benzyl isothiourea derivative by titratin to a phenolphthalein end point and adding the concentrate! solution of the sodium salt to 0.2 grain of the addition component. ACKNOWLEDGMENT
The authors wish to express their appreciation to their director, W. C. Bdnbridge, for his kind encouragment in this work. LITERATURE CITED
Chambers and Scherer, IND.ENQ.CHEM.,16, 1272 (1924). Chambers, E., and Watt, G. W., J . 070.Chem., 6, 376 (1941). Chen and Cross,J. Soc. Dyers Colourists, 59, 144 (1943). Cheronis and Koeck, J . Chem. Educution, 20, 488 (1943). Dewey and Sperry, J. Am. Chem. Soc., 61, 3251 (1939). Donleavy, Ibid., 58, 1004 (1936). Hennion and Schrnidle, Ibid., 65, 2468 (1943). Koch, Milligan, and Zuckerrnan, IND. ENQ. CHEM.,ANAL.ED., 16, 755 (1944). (9) Veibel and Lillelund, Bull. w c . chin. (5), 5, 1153 (1938).
(1) (2) (3) (4) (5) (6) (7) (8)
Uuantitative Determination of Bases by Means of Calomel A p p l i c a t i o n to Lime in Commercial Calcium Arsenate L. N. M A R K W O O D I , H. D. MANN, AND R. H. CARTER United Stater Department of Agriculture, Bureau of Entomology and Plant Quarantine, Washington, D. C.
A
NEW method for the determination of bases depends upon the reaction between the base and calomel (mercurous chloride). Of special interest is the determination of free (uncombined) lime in commercial calcium arsenate, which contains calcium hydroxide in variable amounts up to about 12%. The following exposition, therefore, relates chiefly to the reaction between lime and calomel. Although known for a long time (it is the basis of the preparation of Lotio nigra, N.F.), its application to the determination of basic compounds appears to be new. THEORY
When calcium oxide or hydroxide, calomel, and water are brought together, immediate blackening occurs. The liquid portion of the mixture gives a positive test for chloride ion, and for mercury (with either sodium sulfide or stannous chloride), but a negative test for mercurous ion (with hydrochloric acid). The dissolved mercury is therefore present as mercuric ion. The reaction is probably complicated but may be represented as follows: Ca(0H)t
+ Hg&lr
= HgzO
HgrO = HgO
+ CaClz + HzO
+ Hg
( 1) (2)
The significant feature of the reaction is the formation of soluble chloride, which, with excess of calomel, forms in quantity stoichiometrically equivalent to the hydroxide. Formation of mercuric oxide is visually confirmed by a glimpse of yellow precipitate. This precipitate quickly disappears, however, probably because of the incompatibility of mercuric oxide with soluble chloride, leading to solubility of the oxide as a loose, water-soluble complex. This view is in agreement with the known increased solubility of mercuric oxide in the presence of chloride (1). The formation of mercuric ion requires the breakdown of the mercurous oxide (Equation 2), with consequent formation of elemental mercury, to which the blackening is due. Since the quantity of soluble chloride formed is chemically equivalent to the hydroxide originally present, determination of the latter follows simply by determining the chloride. Excess of calomel does not interfere, since i t is insoluble. The chloride determination is conveniently made by direct titration. with silver nitrate or, where this procedure is inapplicable, by the Volhard method. In either case the dissolved mercury must first be removed. As a practical means of removing mercury ion the solution is treated with a more electropositive metal, zinc being suitable for the purpose. EXPERIMENTAL
1Preaent sddreae, Bureau of Foreign and Domestic Commerce, Department of Commerce. Washington, D. C.
U. 8.
T E ~ TWITH B LIME. Experiments were first made on pure Iceland spar to establish validity of the method. A known weight
