§§ 172, 173. SUBLIMATION, ETC. 181 



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

 alkaloids, see Bnignet.^ Upon j^olarimtlon (§ 185), in particular, 

 see Hesse. 2 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 vm^ |- 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 

 sul)limate 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 

 observalile during the microsiiblimation of alkaloids, see Helwig, 

 Guy, Waddington, and others.'^ 



The crijstaUinc forvi of alkaloids has been closely investigated by 

 Erhard.*^ 



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

 liercentage of platinum and gold in the double chlorides of those 

 metals with some of the more important alkaloids (dried at 

 100°). 



1 Journ. de Pharm, et de Chim. [3], xl. 252, 1862 (Amer. Journ. Pharm, 

 xxiv. 140). 



- Amial. d. Cham, imd Pharm, clxxvi. 89, 1875 (Pharm. Jonrn. and Trans. 

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

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

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

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

 paper subsequently (juoted. 



» Archiv d. Pharm. [3], xiii. 413, 1878. 



•* Pharm. Zeitschr. f. ßussland, 353, 1876. 



•^ Compare Helwig, . ' Das Mikroskop in der Toxicologie,' Mainz ; Guy, 

 Pharm. Journ. and Trans. [2], viii. 718 ; ix. 10, 58, etc. ; Waddington, ibid. 

 [2], ix. 266, 409 ; Stoddart, 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 Hühnef eld's 'Chemie der Bechtspflege, ' Berlin, 1823; 

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

 ' Principles of Forensic Medicine ;' Brand et Chaude, ' Medecine legale,* 

 Paris, 1853. 



