INDiYSl'RIAL A N D ENGINEERING CHEiVISTRY
1272
Vanadium is usually used in ainount,s under 0.5 per cent, and it is then not necessary to apply corrections for the removal of the ordinary 1 cc. of solution for the tests. The number of cubic centimeters used times 3 gives vanadium in tenths of a per cent. The potassium Permanganate solution should be kept at a value of N/17.34 corresponding to 3.22 mg. of iron per cubic centimeter, as this corresponds to 0.1 per cent of chromium, using a 1-gram sample. For the preparation of an exactly N/17.34 solution it is suggested that 18.4 grams of the pure salt be dissolved in 10 liters of pure water. After about 2 months this solution may be standardized by weighing out
~701.16, SO. 12
portions of 0.1932 gram dried, pure sodium oxalate, and this amount should correspond to 50 cc. The value of the ferrous sulfate solution is calculated in terms of the potassium permanganate solution and standardized just before or after use. The arsenic solution is standardized for this special work by adding 0.50 cc. of the potassium permanganate solution when the titration is just ready and then at once titrating to the same bright green color as before described. Both the ferrous sulfate and the arsenic solution should be kept under a neutral atmosphere and a t least once a week the standardizations should be plotted as a function of the time.
Benzylpseudothiourea Salts of Naphthalenesulfonic Acids' By R. F. Chambers and P. C. Scherer BROWNUNIVERSITY, PROVIDENCE, R. I.
hence the solvent used for The benzylpseudothiourea salts of a- and p-monosulfonic acids; this work was 0.2 N hydrovestigation on the suland 1 , 5 , 1,6-, 2.6-, and 2,7-disulfonic acids of naphthalene haw been chloric acid, which effecfonic acids of naphthaprepared and their properties described. These salts may be used as tually prevented hydrolysis. lene it became necessary to a means of identification of the corresponding naphthalenesulfonic It will be evident that the establish a simple means for acids. extreme ease of preparation their identifica,tion. AtThe diflerence in solubility of the two naphthahnemonosulfonic and the characteristic proptention was drawn to two acids in cold alcohol or acetone suggests a convenient method of erties of these salts will papers by Johnson, Donseparation. make them exceedingly useleavey, and SimonsJ2 in Hydrolysis of these salts suggests a method for the preparation of ful as a means of identifying which were described a pure naphthalenesulfonic acids. t h e n a p h t h a1enesulfonic series of salts produced by acids. the interaction of benzylpseudothiourea and the fatty acids, all of which have wellPREPARATION OF BENZYLPSEUDOTHIOUREA defined physical properties. The authors have made the To 76 grams (1 mol) of thiourea dissolved in 200 cc. of 40 benzylpseudotliiourea salts of the more common naphthalenesulfonic acids in the hope of finding a simple means per cent alcohol were added 126.5 grams (1 mol) of benzylchloride with stirring. Reaction took place on slight warmof their determination. Up to the present, the best means of identification has been ing, with the evolution of hydrochloric acid. The mixture the preparation of the sulfone chlorides, with a subsequent was warmed till no more hydrochloric acid was given off and determination of their melting points. This method is rather on cooling the benzylpseudothiourea crystallized out in alcumbersome and is far from convenient or rapid. Ambler most quantitative yield. This was purified by recrystallizaand Wherry3 have described a series of a-naphthylamine tion from 40 per cent alcohol. and P-naphthylamine salts of the sulfonic acids and have deSALTOF CY-NAPHTHALENEMONOSULFONIC ACID vised a qualitative scheme for their identification. Their Ten grams of a-naphthalenesulfonic acid, free of isomers salts have no definite melting points, however, and require and purified by sixfold recrystallization, were dissolved in 400 preparation and separation in boiling, saturated solutions. I n the present work no attempt has been made to outline a cc. of 0.2 N hydrochloric acid. To this solution was added regular analytical procedure, but the physical properties and a warm solution of 8 grams of benzylpseudothiourea in 50 methods of preparation of the benzylpseudothiourea salts cc. of 0.2 N hydrochloric acid. On cooling, the salt of this acid of the more common naphthalenesulfonic acids are given. separated as long orthorhombic needles with positive elongaA simple means of separating the two monosulfonic acids of tion, and after two crystallizations from boiling 0.2 N hydronaphthalene is afforded by taking advantage of the difference chloric acid gave a melting point of 136'-137" C. (uncorrected). Easily soluble in cold 95 per cent alcohol, acetone, glacial in solubility of their benzylpseudothiourea salts in cold alcohol or acetone. The ease with which these salts hydrolyze acetic acid; slightly soluble in hot benzene and ether. For solubility in 0.2 N hydrochloric acid see the table. also affords a n excellent method of preparing the free acid. The amino group in benzylpseudothiourea still retains its SOLUBILITY IN 0.2 N HYDROCHLORIC ACID salt-forming properties and will add one molecule of an acid Temperature c----GRAMSPER I,IT@R-------c. (1) (2) (3) (4 1 (5) to form a salt according to the following equation: 0.2 0.03 0.7 0.7 0 4.4
I
N THE course of an in-
CloHiSOaH
+
HzN\
H
0
I
C-S-C---CoHa HNH I
H
H
\/
=
k Salts of this type were easily hydrolyzed by water and Received July 25, 1924. Presented before Division of Organic Chemistry a t t h e 65th Meeting of t h e American Chemical Society, New Haven, Conn., April 2 t o 7, 1923. 8 THISJOURNAL, 12, 1085 (1920). 1 2
10.1 13.5 17.8 23.5 30.9 40.4 64.0
11)
Sa!t
3)
Salt Salt Salt Salt
?,
'4;
,5;
0.3 0.07 1.2 0.5 0.16 2.2 0.35 3.9 0.8 6.6 1.2 0.77 2.2 1.7 11.5 20.0 3.5 3.6 5.5 34.7 7.8 59.4 8.6 16.8 103.5 13.7 35.7 177 P 21.6 77.6 70.0 of a-naphthnlcnen:ono.iu!fonic acid. o f ~-uap:ithalrnenionoilllionic acid. of tiaphthn!ene-1,3-di.;ulfonic acid. oi na~,htha!erie-2.7-d1,iili~nicarid. of n a p l i t h a l c i i e - 2 , ~ - r l ~ ~ u l i oacid. nic
1.1
5.8 7.7
10 20 30 40 50 60 70 80 90 100
1.6
-
2.4 3.7 5.7 8.8 13.3 20.4 31.0 47.3
December, 1924
INDUSTRIAL A N D ENGINEERING CHEMISTRY
On heating for 120 hours a t 110' C. there was no change in weight, indicating the absence of water of crystallization. SALT OF P-NAPHTHALENEMONOSULFONIC ACID Ten grams of P-naphthalenesulfonic acid were dissolved in 200 cc. of hot 0.2 N hydrochloric acid, and to this solution were adlied 8 grams of benzylpseudothiourea dissolved in 50cc. of 0.2 21' hydrochloric acid. On cooling, the salt separated as long, transparent, flattened prisms with negative elongation, which on recrystallization from 0.2 N hydrochloric acid gave a melting point of 188'-189' C. (uncorrected). Insoluble in cold organic solvents; slightly soluble in hot acetone, alcohol, ether, glacial acetic acid, and benzene. For solubility in 0.2 N hydrochloric acid see the table. On heating for 120 hours a t 110' C. there was no loss in weight, indicating the absence of water of crystalli~ ,at'ion. ,SALT O F ~APHTHALENE-1,5-DISULFOKICACID Ten grams of pure naphthalene-l,5-disulfonicacid were dissolved in 200 cc. of boiling 0.2 N hydrochloric acid and to this solution were added 11 grams of benzylpseudothiourea dissolved in 100 cc. of 0.2 N hydrochloric acid. On cooling, the salt separated as flat, tabular crystals, with multiple twinning and prism or pyramid terminals which on recrystallization from 0.2 N hydrochloric acid gave a melting point of 244 "-245' C. (uncorrected) with some decomposition. Practically insoluble in both hot and cold acetone, ether, benzene, and glacial acetic acid; sparingly soluble in boiling alcohol. For solubility in 0.2 N hydrochloric acid see the table. On heating for 120 hours a t 110" C. there was no loss in weight, indicating the absence of water of crystallization.
1273
SALT O F NAPHTHALENE-2,6-DISULFONICACID
Five grams of 2,6 acid, supplied by J. A. Ambler of the Bureau of Standards, were dissolved in 250 cc. of 0.2 N hydrochloric acid, and to the boiling solution were added 6 grams of benzylpseudothiourea dissolved in 50 cc. of 0.2 N hydrochloric acid. On cooling, the salt separated as fine needles with triangular cross sections, which after repeated crystallizations quite characteristically decomposed a t 200" C. (uncorrected) without melting. Soluble in hot alcohol and glacial acetic acid; practically insoluble in both hot and cold acetone, ether, and benzene. For solubility in 0.2 N hydrochloric acid see the table. On heating for 120 hours a t 110' C. there was no loss in weight, indicating the absence of water of crystallization. SALT OF NAPHTHALENE-l16-DISULFONICACID
The procedure required for the preparation of this salt varied considerably from that of those already described. Five grams of naphthalene-l,6-disulfonicacid were first freed of calcium salts by treatment with sulfuric acid and barium chloride. To the boiling solution of the purified acid, acidified with hydrochloric acid 6 grams of benzylpseudothiourea in 25 cc. of 0.2 N hydrochloric acid were added. On cooling, the salt separated as an oil, which solidified on standing in the ice chest for 2 days. By repeated crystallizations from 0.2 N hydrochloric acid the salt separated as rounded, irregular crystal forms having pointed and square terminations, which melted at 234 "-235 ' C. (uncorrected) with decomposition. Insoluble in cold organic solvents, hot acetone, and ether; sparingly soluble in hot alcohol, benzene, and glacial acetic acid. Solubility in 0.2 N hydrochloric acid could not be determined, owing to its property of separating from solution as an oil. It will be noted that the melting points of the various salts are far enough apart and distinctive enough to give a ready means of identification, and if in addition a determination of the solubilities is carried out, the identification is absolute,
PREPARATION OF PURE NAPHTHALENESULFONIC ACIDS The ease of hydrolysis of these salts suggested a possibility of their use in preparing pure naphthalenesulfonic acids. To this end, 10 grams of technical p-monosulfonic acid of naphthalene were dissolved in 250 cc. of 0.2 N hydrochloric acid, and 7 grams of benzylpseudothiourea dissolved in 50 cc. of 0.2 N hydrochloric acid were added and the resulting salt was recrystallized from 0.2 N hydrochloric acid until it showed a constant melting point of 188"-189" C. (uncorrected). T o this were added 10 cc. of concentrated sodium hydroxide solution. Hydrolysis of the salt took place immediately, with the formation of benzyl mercaptan, which was readily recognized by its odor. Steam was passed through the solu10 20 30 40 60 60 70 80 SO /OO TfZMPZIZATUEE tion until no more mercaptan came over. The solution remaining, after acidification with hydrochloric acid, was twice f3ALT O F NAPHTHALENE-2,7-DISULFONICACID extracted with ether. On concentration of the water layer Fifteen grams of a pure paste furnished by the du Pont and increasing of its acidity to 30 per cent with hydrochloric Company were dissolved in 200 cc. of 0.2 N hydrochloric acid, acid, crystals separated. These were filtered and dried. and to the hot solution were added 10 grams of benzylpseudo- The sulfonamide of these crystals was made and after one thioureai dissolved in 100 cc. of hot 0.2 N hydrochloric acid. recrystallization from alcohol gave a melting point of 210'On cooling, the salt separated as rounded grains with scarcely 212 'C. (uncorrected). Themelting point of the sulfonamide of perceptible remnants of crystal faces, which after repeated p-naphthalenesulfonic acid as given in the literature is 213 'C. On making the benzylpseudothiourea salt of the acid obtained crystallizations showed a constant melting point of 199' above, it was found to have all the characteristics of the beta 200' C. (uncorrected) with decomposition. SolubIe in hot alcohol and glacial acetic acid; practically salt described above. It is quite evident that hydrolysis of the insoluble in cold alcohol, hot and cold acetone, ether, and benzylpseudothiourea salts of the naphthalenesulfonic acids benzene. For solubility in 0.2 N hydrochloric acid see the offers a ready means of preparing these acids in a pure state. Appreciation is expressed to the E. I. du Pont de Nemours table. On heating for 120 hours a t 110' C. the salt showed a loss & Company for financial aid in the form of the du Pont Felin weight equivalent to one molecule of water of crystalliza- lowship, and to J. A. Ambler for pure samples of certain of the tion. acids used.
