408 
COLOUR-TESTS FOR STRYCHNIA, ETC. 
bichromate of potash, produces a yellow solution, which passes 
gradually to a yellow-brown and clear orange. 
4. That the acid, when mixed with a fragment of the 
ferricyanide of potassium, gives a lemon-yellow solution, be¬ 
coming tinged with blue after long exposure. 
5. That the permanganate of potash treated in the same 
way yields with the acid a light-green solution, deepening in 
tint by degrees, then assuming a pink tint at the margin, 
then, after long exposure, becoming brown at the centre and 
lilac at the circumference, and finally, after still longer ex¬ 
posure, presenting a rich scarlet at the centre and a brown at 
the circumference. 
Now, as the succession of colours produced when strychnia, 
sulphuric acid, and either of the five substances just specified, 
are brought into contact, are entirely different from those 
occasioned by the action of sulphuric acid on the five sub¬ 
stances in question, and as, moreover, the strychnia colours 
develop themselves very speedily, there is no valid objection 
to the use of these substances as tests. The yellow tint of 
the acid solution of the bichromate of potash, the lemon-yellow 
tint of the acid solution of the ferricyanide of potassium, and 
the light-green tint of the acid solution of the permanganate 
of potash, offer no impediment to the development of the 
characteristic strychnia colours, and cannot possibly be con¬ 
founded with them. The same observation applies equally to 
the mixture of sulphuric acid with the solutions of these salts. 
When solutions of the strength of ten grains to the ounce of 
distilled water are added to equal quantities of strong sulphuric 
acid, the bichromate of potash yields an orange-coloured 
mixture, the ferricyanide of potassium a lemon-yellow, and 
the permanganate of potash a red-brown. The tints vary with 
the quantity of the acid and of the solutions, and they 
undergo some change on long exposure ; but it may be safely 
alleged that the colours thus produced do not interfere with 
the production of the characteristic strychnia colours, and that 
they cannot possibly be confounded with them. But as for 
medico-legal purposes, it is well to avoid all objections, how¬ 
ever captious, the peroxide of manganese, or the peroxide of 
lead, may claim to be preferred if, on further examination, 
they should be found to possess other properties entitling 
them to a preference. 
{To he continued .) 
