IA'D USTRIAL d S D ElI'GILVEERING CHEMISTRY
March, 1927
ml. Pipet 50 ml. of the solution (0.2-gram sample) into a 300-ml. beaker, add 10 ml. of concentrated nitric acid, and make up t o about 125 ml. with distilled water. Heat to -ompressed Air
boiling, add 5 ml. of a saturated solution of potassium permanganate, and boil for about 5 minutes to free the solution of the evolved chlorine. The potassium permanganate reacts with the hydrochloric acid, forming chlorine, thus removing chlorides from the solution. The solution must
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contain suspended oxides of manganese; if clear, add a little more potassium permanganate and boil the solution again. I n the case of phosphorus-tin, if the solution is boiled too long a flocculent white precipitate will form, which does not redissolve. and the analysis must be restarted. When the solution is free of chlorine, add sodium nitrite in small portions until the solution is decolorized, then 15 ml. of concentrated nitric acid, and boil off the nitrous fumes. Add 10 grams of ammonium nitrate, make up to 150 ml. by volume, heat to 70-80" C., remove from the heat, and immediately add 100 ml. of ammonium molybdate solution. The yellow precipitate of ammonium phosphomolybdate comes down immediately. Allow to stand about 4 hours (or overnight) and filter on a tared, dried Gooch crucible having an asbestos mat. Wash with 100 ml. of a mixture of equal quantities of a 3 per cent nitric acid and a 3 per cent ammonium nitrate solution. Then wash moderately with distilled mater to remove the ammonium nitrate. Dry the Gooch crucible a t 110" C., cool, and weigh. The m-eight of yellow precipitate multiplied by 0.0163 (theory = 0.01653) equals the weight of phosphorus in 0.2gram sample. More or less of any arsenic present in the alloy will be precipitated with, and be counted as, phosphorus.
Naphthalenesulf onic Acids' VII-Hydrolysis
of Naphthalene- 1,6-Disulfonic Acid
By J. A. Ambler a n d J o h n T. Scanlan COLOR
LABORATORY, BUREAU OF
Naphthalene-1,6-disulfonicacid was prepared, isolated from its isomers, a n d crystallized as t h e free acid. This acid was heated in sealed Pyrex tubes with concentrations of sulfuric acid ranging from 1 to 85 per cent a n d a t t e m peratures ranging from 100" t o 230" C. Quantitative determinations were made of t h e degree of hydrolysis over t h e entire range within which any change without charring was observed and t h e results tabulated. The reaction products were determined qualitatively wherever any change occurred. The temperature a t which hydrolysis begins in each concentration of sulfuric acid used was recorded. From t h e results obtained t h e following general rule may be deduced : Naphthalene-1,6-disulfonicacid, when heated until equilibrium is reached with a concentration of sulfuric acid not sufficiently high t o sulfonate naphthalene a t t h e temperature employed and a t a temperature sufficiently high t o hydrolyze the 1,6 acid, is converted directly into naphthalene. If, however, the temperature is high enough to hydrolyze the 1,6 acid and t h e sulfuric acid concentration is sufficient to sulfonate naphthalene a t t h e temperature used, isomeric disulfonic acids are produced. Their nature a n d relative proportions are determined by t h e ratio of sulfuric acid to sulfonic acid, t h e strength of the sulfuric acid, a n d the temperature. The resulting acids are t h e same as would be obtained by the direct sulfonation of naphthalene under identical conditions.
CHEMISTRY, WASHINGTON,
D. C.
The naphthalene-1,6-disulfonicacid cannot exist under the conditions of vapor phase sulfonation of naphthalene, as this reaction is carried out in a n open system a t 220245' C. a n d with sulfuric acid having a concentration of 80 t o 95 per cent. I n t h e steam t r e a t m e n t for t h e elimination of tar, which is carried out a t a temperature slightly above 100" C. in 10 per cent sulfuric acid, the 1,6acid is not affected.
I
K THE course of the work on the vapor phase sulfonation
of naphthalene conducted in the Color Laboratory by Ambler, Lynch, and Haller,2 a question arose as to whether or not naphthalene-1,6-disulfonicacid was formed in the reaction and, if present, whether or not it underwent any change in the subsequent treatment with steam3 to remove the tar. After these facts had been determined, the investigation was extended further because of the unexpected behavior of the l,6 acid on hydrolysis, and in the hope that some light might be thrown upon the mechanism of the reaction by which the sulfo groups are caused t o take new positions in the molecule. As the 1,6 acid contains one sulfo group in the alpha position and one in the beta position, it was assumed that the hydrolysis of this acid would proceed in two steps; that is, the alpha group would be split off first a t lower temperatures, leaving the p-monosulfonic acid, which would then be hydrolyzed to naphthalene a t higher temperatures, thus:
Presented before t h e Division of D y e Chemistry at the 69th Meeting of t h e American Chemical Society, Baltimore, M d . , April 6 t o 10, 1926.
2
THISJOURNAL, 16, 273, 1264 (1924).
Received September 1, 1926.
3
Ambler and Lynch. I b i d . , 17, 61 (1925).
INDUSTRIAL AVO ENGI,VEERIXG CHEMISTRY
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Vol. 19, KO.3
SOIH SOBH Naphthalene- 1,6disulfonic acid
Naphthalene-Psulfonic acid
Kaphthalene
This assumption was based upon the behavior of CY- and pmonosulfonic acids in the commercial process reported by S h r e ~ ein, ~which the alpha acid is hydrolyzed to naphthalene and the naphthalene is removed from the reaction mixture by means of steam a t 160" C., leaving the beta acid unchanged. It was found, however, that the decomposition of the naphthalene-lJ6-disulfonic acid did not proceed in steps. Wherever any hydrolysis occurred naphthalene was produced and no trace of the beta acid could be detected. I n the higher concentrations of sulfuric acid other isomeric disulfonic acids replace the 1,6 acid. These results, together with the quantitative measurements, are given in Tables I, 11, and 111, which also show the temperature at which hydrolysis begins in each concentration of sulfuric acid employed and the temperatures a t which charring, indicated by the presence of SOz,.takes place. The percentages of hydrolysis reported are those which obtain when the reaction takes place in a closed system. P r e p a r a t i o n of M a t e r i a l
The naphthalene-1,6-disulfonicacid was prepared by sulfonating naphthalene in two steps: (1) By Witt's method,5 250 grams of naphthalene were sulfonated with 400 grams of sulfuric acid (sp. gr. 1.84) a t 160165" C. The reaction mixture was held a t this temperature for one hour longer, which, according to Witt, converts most of the alpha acid to the 1,6 acid. (2) The reaction mixture, which consisted principally of the beta acid with a small percentage of the 1,6 acid, was further sulfonated by a slight modification of the method given by Cain and others.6 At the end of the hour's heating 800 grams of cold sulfuric acid (sp. gr. 1.84) was added to the reaction mixture. The material was cooled to 100-110' C , held within that range, and stirred for 5 or 6 hours. The entire reaction mixture was then poured into 500 cc. of cold water, stirred well, and allowed to stand in a cool place for 48 hours. Using nun's veiling instead of filter paper, the free sulfonic acid which had crystallized out was separated from the bulk of the sulfuric acid by filtration with suction. From this point either of the two following methods may be employed: (a) The crude, free sulfonic acid was dissolved in 200 cc. of cold water and filtered. The filtrate was added t o 1250 cc. of cold, saturated sodium chloride solution. The solution was stirred well and allowed to stand for 48 hours. The precipitated sodium salt was then removed by filtration, using suction. -4 solution, saturated a t the boiling point, was made of the crude' sodium salt, neutralized with sodium bicarbonate, more water being added if necessary to keep the salts in solution. Enough boiling water t o increase the volume by one-third was then added (The product was pasty and difficult to filter if precipitated from a solution that was too concentrated.) The solution was then boiled for a n hour with 50 to 100 grams of decolorizing charcoal (Darco), the volume being kept constant, filtered through a hot water funnel, and allowed to cool slowly. The filtrate was colorless and the crystalline product snow-white. Several more crops were obtained by evaporating the filtrate. The volume should not be decreased more than one-tenth for each crop, however, and any insoluble material which separates during evaporation should be filtered off before the solution is allowed t o cool. The crystals were dried in air on porous plate. A yield of 150 grams (14 per cent) was obtained, From the sodium salt, ( N ~ S O ~ ) Z C ~ ~ H thus ~ . ~ obtained H Z O , the barium salt was prepared by double decomposition with barium chloride. The solution was filtered hot t o remove barium sulfate and any barium-l,5disulfonate which might be present, and the barium-1,6-naphthalene disulfonate which separated from the filtrate on cooling was recrystallized from hot water and dried in the air on porous plate. Color Trade J., 1 4 , 42 (1924). Ber., 48, 743 (1915). 6 Cain, "Manufacture of Intermediate Products f o r Dyes," p. 169 (1918); Ewer a n d Pick, German Patent 46,229 (1887); Paul, Z. angcza. Cham., 9, 561 (1896). 4
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