118 
ACETATE OP IRON 
occasionally much perplexed by finding on the addition of 
the acid alone, that the urine assumed a reddish-purple co- 
lour, closely resembling the characteristic one, and the sub- 
sequent addition of the syrup produced no alteration, thus 
rendering the test apparently inapplicable. This alteration 
arises from the action of the acid on the colouring matter of 
the urine, and may always be distinguished from the true 
test-colour by allowing the mixture to repose ; the choleic 
purple is permanent, whilst the other is gradually changed 
to a brown colour. The experimenter will find that where 
the bile is in very small quantity, a considerable excess of 
acid will frequently detect it when a smaller quantity will 
not; the syrup, however, must be added in very small quan- 
tity.— Rid. 
ART. XXXL— ACETATE OF IRON AS A REMEDY FOR ARSENI- 
CAL PREPARATIONS. 
The hydrated peroxide of iron is of admitted efficacy in 
cases of poisoning with uncombined arsenious or arsenic 
acid ; but according to the experiments of Dufios, it is quite 
ineffectual when these acids are combined with bases, as, 
for example, Fowler's solution, or arsenite of potash, or 
arseniate of potash, which last is frequently employed in 
calico-printing, and is consequently easily procured. 
In the uncertainty in which the practitioner may be placed 
as to whether the arsenical poisons be free or combined, it 
is very important to administer the oxide of iron in such a 
form as to produce a favourable result ; to this end it is con- 
venient to employ the peracetate of iron. 
This compound may be prepared by adding to the hy- 
