200 POISONS : THEIR EFFECTS AND DETECTION. [§ 2^1. 
which should have been 30 per cent, of this gas) only gave up 9 per 
cent. Filehne seeks to explain the peculiar colour of the skin by the 
condition of the blood, but the explanation is not altogether satisfactory. 
Some part of the nitro-benzene, without doubt, is reduced to aniline in 
the body—an assertion often made, and as often contradicted ; but it has 
been found in too many cases to admit of question. It would also seem, 
from the experiment on the dog (p. 198), that a conversion into picric 
acid is not impossible. A yellow colour of the skin and conjunctivas, as 
if picric-acid-stained, has been noticed in men suffering under slow 
poisoning by nitro-benzene. 
§ 251. Detection and Separation of Nitro-benzene from the Animal 
Tissues. —It is evident from the changes which nitro-benzene may 
undergo that the expert, in any case of suspected nitro-benzene poisoning, 
must specially look (1) for nitro-benzene, (2) for aniline, and (3) for 
picric acid. The best general method for the separation of nitro-benzene 
is to shake up the liquid (or finely divided solid) with light benzoline 
(petroleum ether), which readily dissolves nitro-benzene. On evaporation 
of the petroleum ether, the nitro-benzene is left, perhaps mixed with 
fatty matters. On treating with cold water, the fats rise to the 
surface, and the nitro-benzene sinks to the bottom ; so that, by means 
of a separating funnel, the nitro-benzene may be easily removed from 
animal fats. The oily drops or fine precipitate believed to be nitro¬ 
benzene may be dissolved in spirit and reduced to aniline by the use of 
nascent hydrogen, developed from iron filings by hydrochloric acid, and 
the fluid tested with bleaching-powder ; or the aniline itself may be 
recovered by alkalising the fluid, and shaking up with ether in the 
separation tube (p. 166); the ether dissolves the aniline, and leaves it, 
on spontaneous evaporation, as an oily, yellowish mass, which, on the 
addition of a few drops of sodic hypochlorite, strikes a blue or violet- 
blue—with acids, a rose-red—and with bromine, a flesh-red. It gives 
alkaloidal reactions with such general reagents as platinum chloride, 
picric acid, etc. Aniline itself may be extracted from the tissues and 
fluids of the body by petroleum ether, but in any special search it will 
be better to treat the organs as in Stas’ process—that is, with strong 
alcohol, acidified with sulphuric acid. After a suitable digestion in this 
menstruum, filter, and then, after evaporating the alcohol, dissolve the 
alcoholic extract in water ; alkalise the aqueous solution, and extract 
the aniline by shaking it up with light benzoline. On separating the 
benzoline, the aniline will be left, and may be dissolved in feebly acid 
water, and the tests before enumerated tried. 
Malpurgo 1 recommends the following test for nitro-benzene :—2 
drops of melted phenol, 3 drops of water, and a fragment of caustic 
potash are boiled in a small porcelain dish, and to the boiling liquid the 
1 Zeit. f. anal. Chem., xxxii. 235. 
