STRYCHNINE. 
345 
§ 4°6.] 
mate of potash (if allowed to stand over-night) a marked precipitate, 
dissimilar to all others, except those of lead and baryta chromates, neither 
of which can possibly occur if any of the processes described are followed. 
3. If the chromate just described is treated on a porcelain plate 
with a drop of pure strong sulphuric acid, a deep rich blue colour, 
passing through purple into red, rapidly makes its appearance. This 
colour possesses an absorption spectrum (figured at p. 64). Dr Guy, 
neglecting intermediate colours, aptly compares the succession—(1) to 
the rich blue of the Orleans plum ; (2) to the darker purple of the 
mulberry ; and (3) to the bright clear red of the sweet orange. These 
characters—viz. alkalinity, bitterness, and the property of precipitation 
by potassic chromate in a definite crystalline form, the crystals giving 
the colours detailed—belong to no other substance known save strych¬ 
nine, and for all purposes sufficiently identify the alkaloid. The same 
colour is obtained by mixing a drop of sulphuric acid with strychnine 
and a crystal, or speck, of any one of the following substances :—Ferri- 
cyanide of potash, permanganate of potash, peroxide of lead, peroxide of 
manganese, and cerous hydroxide. 
Potassic permanganate and sulphuric acid is the most delicate, 
and will detect 0001 mgrm. of strychnine ; cerous hydroxide is, on 
the other hand, most convenient, for cerous hydroxide is white ; all 
the others have colours of their own. Cerous hydroxide is prepared 
by dissolving cerium oxalate in dilute sulphuric acid and precipitating 
with ammonia, filtering and well washing the precipitate ; and the 
latter may be used while moist, and responds well to t Jq- mgrm. of 
strychnine. 
The influence of mixtures on the colour reactions of strychnine has 
been studied by Fliickiger, who states :— 
“No strychnine reaction appears with sulphuric acid containing 
chromic acid (made by dissolving 0*02 grm. of pot. bichromate in 10 c.c. 
of water, and then adding 30 grms. strong sulphuric acid) when brucine 
and strychnine mixed in equal parts are submitted to the test; it 
succeeds, however, in this proportion with sulphuric acid containing 
potassium permanganate (04)2 grm. pot. permanganate in 10 c.c. of 
water, and 30 grms. of strong sulphuric acid). 
“ If the brucine is only one-tenth of the mixture, the blue-violet 
colour is obtained. A large excess of atropine does not prevent or 
obscure the strychnine reaction. A solution of 1 mgrm. atropine 
sulphate evaporated to dryness, together with 5 c.c. of a solution of 
strychnine (1 : 100,000), has no influence on the reaction, neither in the 
proportion of 1 mgrm. to 1 c.c. of the same solution ; neither has 
cinchonine nor quinine any effect. 
“ Morphine obscures the reaction in the following proportions :— 
“ A solution of O'Ol mgrm. strychnine evaporated with a solution of 
