Licence: Public Domain Mark
Credit: Medical jurisprudence / by Alfred Swaine Taylor. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
941/968 (page 927)
![cyanide of potassium and carbonate of soda, for the sulplmret of arsenic, has been recommended. Dr. Edmund Davy of Dublin has advised as a reducing agent for either of the above com- i pounds, the ferrocyaiiide. of putatmium, thoroughly dried at 212^. I (Chemical iSiews, .May li, 1861, p. 288.) This salt, so far as I ' know, has not been before employed for such a purpose by any chemist. The results are satisfactory. The flux is clean, of a light colour; it does not adhere to the sides ot the reduction-tube, and when mi.xed in the proportion of two parts of ferrocyaninde to one of arsenious acid or of the sulphuret, and the mi.xture is heated to full redness, a well defined ring of metallic arsenic is easily ob- tained. The mi.x-ture becomes at first black, it then fuses, and the metallic arsenic is sublimed and deposited in a cool part of the tube. The heat of a spirit-lamp is suflicient, but a Bunsen's burner gives a better result. The ferricyanide of po- tassium well-dried, equally answers the purpose of a reducing agent, but it has no advantages over the dried ferrocyanide. 'i'he ferrocyanide of potassium should itself be first tested by heating it in a reduction-tube. It undergoes similar changes, by heat, it darkens in colour, fuses and leaves a residue, which ihies to a greenish black colour, but it yields no metallic sub- limate whatever. 1 have ti-sted the fused residue in the tube after the ferrocyanide with arsenic had been heated to full redness for some time. There was a mere trace of arsenic left, a result which is invariably observed when the reduction of arsenic takes place in contact with an alkali or an alkaline carbonate. Piifji^ 0.3. T/ie detection of arsenic in. copper.— The method described at the foot of the page for the detection in and sepa- ration of arsenic from metallic copper was, I believe, first de- vised by myself and employed in the analyses for arsenic required in Uiy. v. SmcAkiUKl, in June and July 18.59. It has an advantage over other methods in this respect, that it requires the use of only one chemical compound (hydro- chloric acid), the purity of which may be easily tested. It was in the summer of 18.')9 that by this new process 1 de- uu>nstrated to my friend Professor Urande the ju'esence of arsenic in samjjles of copper which liad been su]ii)lied to the Royal .Mint as I'ree from that metal. 1 also delecfed it at the same time by this jiroccss in samples of copper furnished to me by five distinguished chemists |)ractising in I'higland, Ire- land, and Scotland. I'iKje OC). DistJlldtinn-procexa for (irttcnic 'lhe great facility with which arsenic was entirely separated from metallic cojiper by distillation with liydiochloric acid, in the process referred t{) in the preceding paragraph, induced me at the same time](https://iiif.wellcomecollection.org/image/b21935221_0941.jp2/full/800%2C/0/default.jpg)
