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.
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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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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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T H E J O U R N A L OF I J D U S T R I A L AiVD E N G I N E E R I N G C H E M I S T R Y
order t o decompose completely t h e calcium picrate during t h e steam distillation. I t was obviously desirable t o know what happened t o this excess of bleaching powder during t h e steam distillation. T h e following experiments establish t h e approximate rate a t which active chlorine disappears during steam distillat*on, first, in t h e residue left after t h e preparation (of chloropicrin, and, second, in a more concentrated solution containing t h e same concentration of bleaching powder as t h a t originally present in t h e chloropicrin stills. Finally, analyses were made t o determine t h e concentration of active chlorine remaining in each of t h e t e n plant stills a t t h e end of t h e distillation which removed t h e chloropicrin from t h e sludge. TABLEI-PERCENTAGES After Distilling off Chloropicrin 0.0330 0,0505 0.0459
OF ACTIVII CHLORIKE After 0.5 H r . Steam After 1 5 Hrs. Steam Distillation Distillation 0.0262 0.0157 0.0218 0.0172 0.0242 0.0160
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proximate d a t a for the rate a t which bleaching powder is decomposed by steam. When higher initial concentrations of t h e hypochlorite were employed, t h e rate of decomposition with steam was noticeably higher. The initial concentrations shown in Table I1 correspond t o those employed in t h e plant. TABLE11-PERCENTAGES INITIAL 6.98 6.18
O F ACTIVE CHI.ORINB After 1 H r . Steam After 2 Hrs. Steam Distillation Distillation 2.52 ’ 0.714 3.21 0.747
Samples of t h e sludge left in t h e chloropicrin stills a t t h e end of t h e distillat.ion were analyzed. T h e conditions under which the various runs were made and t h e concentrations of t h e active chlorine based upon the weight of t h e sludge are shown in Table 111. The results show t h a t t h e concentration O E active chlorine is very low in all cases. TABLE I11 No. of Max. Temp. during Still Distillation 1 . . . . . . . . . . . . . . . . 102.0 2 . . . . . . . . . . . . . . . . 103.5 3 . . . . . . . . . . . . . . . . 104.0 4 . . . . . . . . . . . . . . . . 105.0 5 . . . . . . . . . . . . . . . . 100.0 6 . . . . . . . . . . . . . . . . 104.0 7 . . . . . . . . . . . . . . . 104.0 8 . . . . . . . . . . . . . . . . 105.0 9 . . . . . . . . . . . . . . . . 101.0 10 . . . . . . . . . . . . . . . . 104.0
The residue left in the flask when chloropicrin was prepared as described in t h e preceding paper was analyzed for available chlorine b y t h e iodometric method The sludge was then subjected t o steam distillation for periods of one-half and one and onehalf hours, respectively. T h e analyses furnish ap-
Percentage Active Cl in Sludee 0.28 0.24 0.28 0.28 0.285 0.32 0.29 0.29 0.26 0.22
ORIGINAL PAPERS A STUDY OF T H E REACTIONS OF COAL SULFUR IN T H E COKING PROCESS1~2
cluded t h a t a somewhat greater percentage of t h e organic sulfur was volatilized t h a n t h e inorganic, but no very sharply cut difference was noticeable. By Alfred R. Powell J. R. Campbell’ stated t h a t most of t h e coal sulfur EXPERIMENT STATIOX,BUREAUOF MINES, PITTSBURGH, PA. was present as pyrite, t h a t 42 per cent of this was PREVIOUS INVESTIGATIONS volatilized during t h e coking process, and t h a t t h e The sulfur of coal has now been definitely established remainder was left in t h e coke as pyrrhotite. He also t o exist as pyrite or marcasite, FeS2, organic sulfur, stated t h a t most of t h e organic sulfur was retained and a rather small amount of sulfates, a n d accurate in t h e coke. methods have been devised for t h e determination of Some tentative conclusions have been drawn by S. these different forms.3 T h e behavior of each form W. Parr2 concerning sulfur in t h e coking process during t h e destructive distillation of coal is of theoreti- from his work on t h e low temperature carbonization cal interest, as well as of t h e greatest technical impor- of coal. He states t h a t “the organic sulfur in t h e tance, since t h e reactions of t h e coal sulfur will deter- raw coal and half of t h e sulfur of FeS2 is for t h e most mine t h e percentage of sulfur left in t h e coke and t h e part discharged a t relatively low temperatures.” This nature and t h e amount of t h e sulfur compounds in occurs at about 500’ C. At about 7 o o o , t h e sulfur the by-products. of t h e FeS formed from t h e FeSz is taken up by carbon, The percentage of coal sulfur expelled during t h e leaving free iron in t h e coke. coking process varies over wide limits, and this variaI t therefore appears t h a t different investigators tion ha:; always been supposed t o be due t o different have obtained widely divergent results, and have relative percentages of sulfur forms in t h e ~ 0 a l . 4 advanced many different theories as t o t h e reactions LcI’Calliim states6 t h a t he separated coal into different undergone by t h e coal sulfur during carbonization. fractions b y specific gravity methods, thereby securing The present investigation was undertaken with t h e a partial separation of t h e organic and t h e inorganic idea of carbonizing a variety of coals under carefully sulfur. From coking tests on these fractions he con- controlled conditions, and studying t h e character and ’ Published b y permission of the Director of the U. s. Bureau of Mines. amount of t h e various sulfur compounds formed. 2 Presented by title a t the 59th Meeting of the American Chemical Since these analyses were t o be made over every Society, St. Louis, Ma., April 12 t o 16, 1920. period of t h e carbonization process, a complete and 3 A . R . Powell and S . W. Parr, “A Study of the Forms in Which Sulfur Occurs in Coal,” University of Illinois, Engineering Experiment Station, detailed picture could be obtained of t h e changes occurBuZZrlin 111 (1919). ring in t h e coal sulfur. Fulton, “Treatise on Coke,’’ International Textbook Co., Scranton, Pa., 1905,pp, 38-40. 5 Chent. Eng., 11 (1910), 27.
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Bull A m I m t Mznzng Ens., 1916, 177 I b i d . , 1919, 1807.
