278 POISONS : THEIR EFFECTS AND DETECTION. [§ 336 . 
such solution on the addition of a caustic alkali. The aqueous solution 
acts in many respects like ammonia, saturating acids fully, and may 
therefore be in certain cases estimated by titration, 49 parts of H 2 S0 4 
corresponding to 162 of nicotine. 
Alcohol and ether dissolve nicotine in every proportion ; if such 
solutions are distilled, nicotine goes over first. The salts which it forms 
with hydrochloric, nitric, and phosphoric acids crystallise with difficulty ; 
tartaric and oxalic acids form white crystalline salts, and the latter, 
oxalate of nicotine, is soluble in alcohol, a property which distinguishes it 
from the oxalate of ammonia. The best salts from which to regenerate 
nicotine in a pure state are the oxalate and the acid tartrate of 
nicotine. 
Hydrochloride of nicotine is more easily volatilised than the pure 
base. Nicotine is precipitated by alkalies, also by many oxyhydrates, 
lead, copper, etc. It is also precipitated by tannin and gallic acid ; an 
alcoholic solution of tannin completely precipitates an alcoholic solution 
of nicotine. By the action of light, it is soon coloured yellow and brown 
and becomes thick, in which state it leaves, on evaporation, a brown 
resinous substance, only partly soluble in petroleum ether. 
A very excellent test for nicotine, as confirmatory of others, is the 
beautiful, long, needle-like crystals obtained by adding to an ethereal 
solution of nicotine a solution of iodine in ether. The crystals require a 
few hours to form. The various iodides, partly intramolecular and partly 
additive, and the conditions under which they form, have been studied 
by Kippenberger. 1 
Chlorine gas colours nicotine blood-red or brown ; the product is 
soluble in alcohol, and separates on evaporation in crystals. 
Cyanogen also colours nicotine brown ; the product out of alcohol is 
not crystalline. Platinic chloride throws down a reddish crystalline pre¬ 
cipitate, soluble on warming. A drop of nicotine poured on dry chromic 
acid blazes up, and gives out an odour of tobacco camphor ; if the ignition 
does not occur in the cold, it is produced by a gentle heat. A solution 
of nicotine in chloroform on the addition of iodine forms fine red crystals 
(Roussin’s crystals), C 10 H 14 N 2 HI,I 2 +z CHC1 3 : the best proportions 
seem to be the reaction of 2 atoms iodine on 1 molecule of nicotine. 
It is scarcely possible to confound nicotine with ammonia, by reason 
of its odour ; and, moreover, ammonia may always be excluded by 
converting the base into the oxalate, and dissolving in absolute alcohol. 
On the other hand, a confusion between coniine and nicotine is apt 
to occur when small quantities only are dealt with. It may, however, 
be guarded against by the following tests : — 
1. If coniine be converted into oxalate, the oxalate dissolved in 
alcohol, and coniine regenerated by distillation (best in vacuo) with 
1 Zeit. anal. Chemie, 1903, p. 232. 
