T H E J O U R N A L O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y Vol.
1068
CONTROL EXPERIMENTS IN CHLOROPICRIN MANUFACTURE. I-THE EFFECT OF VARYING QUANTITIES OF LIME UPON THE YIELD OF CHLOROPICRIN1 By H. L. Trumbull, G. T. Sohl, W. I. Burt and S. G. Seaton CHEMICALLABORATORY, EDGEWOOD ARSENAL,EDGEWOOD,MARYLAND Received July 14, 1920
I n t h e manufacture of chloropicrin a t t h e Edgewood Arsenal during t h e summer of 1918, t h e method involved t h e following steps: The preparation of t h e soluble lime salt of picric acid b y mixing picric acid a n d an excess of lime with water, t h e preparation of a sludge of water and bleaching powder, t h e mixing of these two solutio n t h e large reactors, and t h e digestion a n d ste distillation which gave chloropicrin i n t h e distillate. The production of large quantities of chloropicrin b y this method was realized, although t h e employment of t h e violently explosive picric acid necessitated t h e exercise of care and vigilance a t all times. To avoid danger and t o decrease expense, it was necessary t o conduct t h e reaction in such a way as t o produce t h e highest yield of t h e final product. The employment of calcium picrate instead of picric acid in t h e reaction was in harmony with t h e dictates of safety, since t h e lime salt is much more soluble t h a n t h e free acid (or even t h e sodium salt), and t h e difficulties-involved in working in dilute solutions or in nonhomogeneous suspensions were thereby completely avoided. I t seemed t h e part of wisdom t o prepare solutions in t h e presence of an excess of lime which served as a margin of safety in t h e operation of the process. The laboratory was requested t o investigate t h e effect of adding varying quantities of lime upon t h e yields of chloropicrin. EXPERIMENTAL METHOD
The materials employed for t h e preparation of chloropicrin were carefully analyzed, with t h e following results: L i m e . . . . . . . . . . . . . . . . 9 5 . 5 4 per cent CaO Picric a c i d . , . , . . , . , , , . . . 9 9 . 8 0 per cent free acid, no sulfates Bleaching powder 3 3 . 3 0 per cent available chlorine Sample 1 . .. . . . Sample 2 . . . . . , . . . . . . . 3 2 . 2 1 per cent available chlorine Sample 3 , . , . . . . , . , . , . 3 3 . 3 per cent available chlorine The best yields-were obtained when t h e bleaching powder was madefup t o a thick paste with water, and t h e solution of picric acid or calcium picrate, as t h e case might be, was added in small portions with shaking and cooling, t h e temperature being kept below 30' C. The loss of chloropicrin, was prevented b y keeping t h e flask tightly stoppered during t h e addition. For a neutral solution 3 0 0 g. of bleaching powder, 30 g. of picric acid, and 3.8; g. of lime were employed. Before, conducting t h e steam distillation, t h e flask was connected t o t h e condenser and gently heated until t h e yellow color had disappeared. Too rapid heating a t this point not only led t o lower yields of chloropicrin but also left a yellow residue, which was not decolorized upon subsequent treatment with bleaching powder, followed by steam distillation. From t h e distillate t h e chloropicrin lower layer was drawn off and weighed, the amount dissolved in t h e aqueous layer being estimated from t h e solubility curve. Ordinarily, t h e latter quantity increased t h e t
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Published by permission of the Chief of the Chemical Warfare Service.
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t h e yield by about I per cent. Yields are reported on t h e basis of the ratio b y weight of chloropicrin t o picric acid. To illustrate t h e importance of keeping t h e mixture cool during t h e picric acid or picrate addition, four experiments were conducted in which the picric acid was added in one step without cooling, t h e ratios obtained being 1.68, 1.68, 1.67,and 1.6j. Upon repetition of t h e experiment with cooling and stepwise addit.ion of t h e picric acid, t h e ratio was 1.75 in two experiments. I n all t h e experiments, 30 g. picric acid, 300 g. bleaching powder, and 1 2 0 0 g. water were employed. The yields obtained b y varying t h e amount of lime are shown in t h e following table: AMOUNT OF LIME
0 3 . 8 5 g . (no excess).
... , ., . . ... ,
, ,
U't. ~ of Chloropicrin _ _ Wt. of Picric Acid 1.76 1.75 1.75 . , . , . . , . , . . .. 1 . 7 6 1.80 1 71
4 . 2 4 g. (10 per cent excess). , , . . . . . , . . . . . , . . ,
5.00 g. (30 per cent excess)
..
..
1.72 1.76
1.78 1.78 1.79 1.69 1.71 1.76 1.77 1.76 1.72 1.69 1.67 1.78 1.79 1.82 1.79 1.78 1.78
c0 NCLUSI 0 N Under conditions which approximated a s closely as possible those employed in t h e chloropicrin plant a t Edgewood Arsenal, an excess of lime had no influence upon t h e yield of chloropicrin. Indirect support of this conclusion was furnished b y some experiments conducted by Rowland J. Clark, a t Edgewood, which showed t h a t upon refluxing chloropicrin with water or calcium hydroxide very little hydrolysis occurs. After refluxing for one hour with water, i t was found by estimating t h e chloride ion liberated, t h a t 0.2 I per cent of t h e chloropicrin was hydrolyzed. With calcium hydroxide solutions t h e hydrolysis which occurred in one hour was practically t h e same as with water, v i z . , 0.24 per cent. The absence of nitrites in the residue from t h e refluxing with calcium hydroxide was established b y a qualitative test. This f a c t is somewhat surprising, since a t t h e boiling point of chloropicrin brown fumes are evolved, frequently with explosive violence. CONTROL EXPERIMENTS IN CHLOROPICRIN MANUFACTURE. 11-ACTIVE CHLORINE IN THE SLUDGE FROM THE MANUFACTURE OF CHLOROPICRIN1 By H. L. Trumbull, S. G. Seaton and Howard Durham CHGMICAL LABORATORY, EDGEWOOD ARSENAL, EDGEWOOD, MARYLAND Received July 14, 1920
I n t h e manufacture of chloropicrin it was necessary t o use a fairly large excess of bleaching powder in 1
Published by permission of the Chief of the Chemical Warfare Service.
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