140 ODOROGRAPHIA. 
septics. Thallin is a liquid base, first prepared in 1885 by Prof. 
Skraup, its chemical formula is CyH,)N(OCH3), and its systematic 
name Tetrahydroparachinanisol. It has a strong odour resembling 
coumarin, and forms well-defined salts with acids. These salts, 
which are yellowish-white crystalline powders, are all freely 
soluble in water, and have the property of forming intensely 
emerald-green solutions; hence, for brevity, the adopted name 
Thallin, from @adXos, a green twig. Ferric chloride produces the 
colour. Sodium thiosulphate changes the green tint into violet, 
and then into wine-red; oxalic acid, at ordinary temperatures, 
into pale yellow, deepening into saffron on heating. 
According to the Patent Specification, parachinanisol (from 
which Thallin is formed by hydrogenation) is obtained by heating 
together paramidoanisol, paranitroanisol, and acrolein*. 
By reducing agents Parachinanisol takes up four atoms of 
hydrogen, forming Thallint. At ordinary temperatures thallin 
is an oily liquid, solidifying when cooled to yellowish crystals. 
Thallin sulphate is a yellowish-white crystalline powder, with a 
bitter and intensely aromatic taste, and a peculiarly persistent 
odour similar to coumarin. Like the base itself, this salt in a 
one per cent. solution is coloured emerald-green. 
Thallin tartrate occurs as a yellowish-white crystalline powder 
with an odour reminding one of anise and coumarin. 
The cdour of coumarin is observed in anisic aldehyde, a heavy 
oil (sp. gr. 1:09) of an amber colour, produced by the action of 
weak nitric acid on oil of anise. The crude product contains 
anisic acid, which may be removed by washing the oil, carefully 
distilling it, and agitating the distillate with weak potash lye. 
* Acrolein is prepared by distilling in a capacious retort a mixture of glyce- 
rine with phosphoric anhydride. The vapours must be condensed in a properly 
cooled receiver, luted on to the retort, and provided with a tube opening into a 
chimney having a good draught. The distilled liquid separates into two layers, 
the upper one consisting of acrolein, and the lower one of an aqueous solution 
of the same mixed with a quantity of acrylic acid. The distillate, after diges- 
tion with finely powdered litharge to neutralize the acid, must be rectified by 
the heat of a water-bath, and submitted to a second rectification from calcic 
chloride. All these operations must be conducted in vessels filled with carbonic 
anhydride, because acrolein becomes rapidly oxidized when exposed to the air. 
It is a clear colourless liquid, lighter than water, and when pure is neutral to 
test-paper. It boils at about 125° Fahr. 
t Archives der Pharmacie, xxii. p. 840, and Pharm. Journ. [3] xv. p. 575. 
