From another canine corpse, three days laid in an oven, and left for twenty-seven days at the ordinary temperature, 5·1 mgrms. were recovered out of a fatal dose of 38 mgrms.
The estimation was in each case performed by titrating the distillate with argentic nitrate, the sulphur compounds having been previously got rid of by saturating the distillate with KHO, and precipitating by lead acetate.
Venturoli[258] has, on the contrary, got good quantitative results without distillation at all. A current of pure hydrogen gas is passed through the liquid to be tested and the gas finally made to bubble through silver nitrate. He states that the whole of the hydric cyanide present is carried over in an hour. Metallic cyanides must be decomposed by sulphuric acid or tartaric acid. Mercury cyanide must be decomposed with SH2, the solution acidified with tartaric acid, neutralised with freshly precipitated calcic carbonate to fix any ferro- or ferri-cyanides present, and hydrogen passed in and the issuing gases led first through a solution of bismuth nitrate to remove SH2 and then into the silver solution.
[258] L’Orosi. xv. 85-88.
§ 267. How long after Death can Hydric or Potassic Cyanides be Detected?—Sokoloff appears to have separated prussic acid from the body of hounds at very long periods after death—in one case sixty days. Dragendorff recognised potassic cyanide in the stomach of a hound after it had been four weeks in his laboratory,[259] and in man eight days after burial. Casper also, in his 211th case, states that more than 18 mgrms. of anhydrous prussic acid were obtained from a corpse eight days after death.[260] Dr. E. Tillner[261] has recognised potassic cyanide in a corpse four months after death. Lastly, Struve[262] put 300 grms. of flesh, 400 of common water, and 2·378 of KCy in a flask, and then opened the flask after 547 days. The detection was easy, and the estimation agreed with the amount placed there at first. So that, even in very advanced stages of putrefaction, and at periods after death extending beyond many months, the detection of prussic acid cannot be pronounced impossible.
[259] Dragendorff, G., Beitr. zur gericht. Chem., p. 59.
[260] Casper’s Pract. Handbuch der gerichtlichen Medicin, p. 561.