§§ 172, 173. SUBLIMATION, ETC. 181 



§ 172. Other Tests. — For information eoncerning optical tests for 

 alkaloids, see Buignet.^ Upon jtolarizdtion (§ 185), in particular, 

 see Hesse. ^ For the absorption spectra observable in colour-re- 

 actions of alkaloids, see Meyer^ and Poehl.* 



The temperature at which alkaloids sublime has been deter- 

 mined by Armstrong, in an apparatus similar to that described in 

 § 17 for ascertaining the melting-point of fats. The alkaloid is 

 placed on a. coverslip, to which a glass ring^ to | inch high is 

 cemented, and on which a second coverslip is laid. As soon as a 

 cloud is observed on the latter, the temperature is noted. The 

 sublimate is subsequently examined microscopically as to its 

 crystalline or amorphous character. Mercury or easily fusible 

 alloys may be used to heat the alkaloid. For the appearances 

 observable during the tnierosuMiirtafion of alkaloids, see Helwig, 

 Guy, Waddington, and others.^ 



The crystalline form of alkaloids has been closely investigated by 

 Erhard.* 



§ 173. Platinum and Gold-salts. — The following list contains the 

 percentage of platinum and gold in the double chlorides of those 

 metals with some of the more important alkaloids (dried at 

 100°). 



' Joum. de Pharm. ei de Chim. [3], xl. 252, 1862 (Amer. Journ. Pharm. 

 xxiv. 140). 



^ Annal. d. Chem. und Pharm. clxxvi. 89, 1875 (Pharm. Joum. and Trans. 

 [3], tK. 191), and cxcii. 161, 1878. See also OtidemaTis, ibid, clxxxii. 33, 

 1877 (Year-book Pharm. 75, 1878) ; Afch. Neerland. des Sciences exactes et 

 naturelles, x. 193, 1875 ; and amongst older works that in particular of 

 Bouchardat, Annales de Chimie e% de Physique [3], ix, 213. See also Poehl's 

 paper subsequently quoted. 



» Archivd. Pharm. [3], xiii. 413, 1878. 



* Pharm. Zeitschr.f. Kussland, 353, 187-6. 



° Compare Helwig, ' Das Mikroskop in der Toxicologie,' Mainz ; Guy, 

 Pharm. Joum. and Trans, [2], ™i. 718 ; ix. 10, 58, etc. ; Waddington, ibid. 

 [2], ix, 266, 409 ; 3toddart, ibid. 173 ; Brady, ibid. 234 ; Ellwood, ibid. [2], 

 X. 152 ; Ledgewick, Brit. Rev. Ixxxi. 262. 



' N. Jahrb. f. Pharm. xxv. 129, etc. ; xxvi. 9, etc., ' 1866. Amongst the 

 older works are Hnhnefeld's 'Chemie der Eechtspflege,' Berlin, 1823; 

 Anderson, Chem. Can tralblatt, 591, 1848; Taylor, 'On Poisons;' Guy, 

 'Principles of Forensic Medicine;' Brand et Chaud^ 'M^decine .legale,' 

 Paris, 1853. 



