264 POISONS : THEIR EFFECTS AND DETECTION. [§ 32I. 
duced rather by decomposition than by true sublimation, condense on 
the upper disc at 185° and above. 
Saponin neither melts nor sublimes ; it begins to brown about 145°, 
is almost black at 185°, and quite so at 190°. 
Delphinine begins to brown about 102° ; it becomes amber at 119°, 
and melts, and bubbles appear. There is no crystalline sublimate ; 
residue not characteristic. 
Pilocarpine gives a distinct crystalline sublimate at 153° ; but thin 
mists, consisting of fine dots, may be observed as low as 140°. Pilo¬ 
carpine melts at 159° ; the sublimates at 160° to 170° are in light yellow 
drops. If these drops are treated with water, and the water evaporated, 
feathery crystals are obtained ; the residue is resinous. 
Theine wholly sublimes ; the first sublimate is minute dots, at 79° ; 
at half a degree above that very small crystals may be obtained ; and 
at such a temperature as 120°, the crystals are often long and silky. 
Theobromine likewise wholly sublimes ; nebulse at 134°, crystals 
at 170° and above. 
Salicin melts at 170° ; it gives no crystalline sublimate. The melted 
mass remains up to 180° almost perfectly colourless ; above that tem¬ 
perature browning is evident. The residue is not characteristic. 
Picrotoxin gives no crystalline sublimate. The lowest temperature 
at which it sublimes is 128° ; the usual nebulae then make their appear¬ 
ance ; between 165° and 170° there is slight browning ; at 170° it melts. 
The residue, slowly cooled, is not characteristic. 
Cantharidin sublimes very scantily between 82° and 83° ; at 85° the 
sublimate is copious. 
The active principles of plants may, in regard to their behaviour to 
heat, be classed for practical purposes into— 
1. Those which give a decided crystalline sublimate : 
(a) Below 100°, e.g. cocaine, theine, thebaine, cantharidin. 
(b) Between 100° and 150°, e.g. quinetum. 
(c) Between 150° and 200°, e.g. strychnine, morphine, 
pilocarpine. 
2. Those which melt, but give no crystalline sublimate : 
(а) Below 100°, e.g. hyoscyamine, atropine. 
(б) Between 100° and 150°, e.g. papaverine. 
(c) Between 150° and 200°, e.g. salicin. 
( d ) Above 200°, e.g. solanine. 
3. Those which neither melt nor give a crystalline sublimate, e.g. 
saponin. 
§321. Melting-point. —The method of sublimation just given also 
determines the melting-point; such a determination will, however, 
seldom compare with the melting-points of the various alkaloids as 
