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(H<rC1 5 ) 8 ; while the cadaverine salt seems to have four mercuric 

 chloride molecules. Moreover the author has converted cada- 

 verine into piperidine and observed its identity with that from 

 the other base. Its ehlorhydrate fused at 237°, and it formed a 

 beautifully crystallized double platinum salt fusing at 194°-195°. 

 — Ber. Berl. Ghem. Ges., xix, 2584-2586, October, 1886. g. f. b. 



7. On a method of obtaining Hydrochloric acid absolutely 

 free from Arsenic. — The large quantity of hydrochloric acid 

 which is required to destroy the organic matter by the process 

 of Fresenius and Babo in cases of poisoning, renders it necessary 

 to purify this acid from arsenic with the greatest care. Otto, 

 after giving the various methods proposed for doing this, calls 

 attention to one which he has recently adopted. It was sug- 

 gested by observing that the crude acid of commerce, after treat- 

 ment with hydrogen sulphide and fractional distillation, con- 

 tained not a trace of arsenic. Hence it appeared that the impuri- 

 ties present in the crude acid enabled the hydrogen sulphide to 

 precipitate the arsenic completely. Experiment confirmed this 

 conjecture and proved that the last minute trace of arsenic pres- 

 ent in the purest hydrochloric acid of commerce is precipitated 

 as arsenous sulphide in the presence of other impurities; and 

 further that by adding to the acid before precipitation some sub- 

 stance precipitable by hydrogen sulphide, this last trace of 

 arsenic can be absolutely removed. To test this question thor- 

 oughly, seven portions of hydrochloric acid, of two liters each, 

 of sp. gr. 1-12 (one portion of which had been shown by Marsh's 

 test to give a mirror corresponding to about one-tenth of a milli- 

 gram of arsenous oxide, were treated as follows: (a) with 5 grams 

 of a ten-per cent solution of ferric chloride, (b) with 2 grams of 

 potassium dichromate, (r) with 2 grams mercuric chloride, (d) with 

 1 gram cadmium sulphate, (e) with 1 gram copper sulphate, (f) 

 with 30 grams of a saturated solution of sulphurous acid, and (g) 

 with 30 grams of a hall-per cent solution of chlorine. These por- 

 tions of acid were then saturated with hydrogen sulphide, and 

 allowed to stand for some time. They were then filtered and the 

 filtrate tested for arsenic without giving the slightest trace of a 

 mirror. The precipitates from portions #, #, /', and g showed the 

 presence of arsenic. Indeed even the presence of arsenous oxide 

 itself determines the absolute precipitation of traces of arsenic from 

 the acid. Two liters of the same acid as above were treated with 

 0*2 gram As 2 3 and then with hydrogen sulphide. The filtrate 

 was free from arsenic. To obtain pure hydrochloric acid the 

 author advises that the crude acid of commerce be diluted to the 

 sp. gr. of 1*12, treated with washed hydrogen sulphide to satura- 

 tion, allowed to stand for 24 hours at 30°-40°, again treated with 

 H 2 S, and allowed to stand, the clear liquid decanted and carefully 

 distilled, reserving the middle portions. In five liters of acid thus 

 purified the author could detect no trace of arsenic by Marsh's 

 test.— Ber. Berl. Ghem. Ges., xix, 1903-1919, July, 1886. g. f. b. 



