528 Mr. PoRRETT on the nature of the Salts 
is not decomposed at the boiling temperature, nor in the least 
altered by carbonic acid. To the black oxide of iron, there- 
fore, existing in this salt, chemists have attributed its superior 
permanency to the simple prussiate, and also its conversion 
to the neutral state. The latter effect of the oxide of iron is 
without a parallel in chemistry, no other alkaline salt is known 
which can be rendered neutral by the mere addition of black 
oxide of iron, which in all other instances will neutralize acids 
instead of alkalies. This however is not the only anomaly 
which the triple prussiates present, the following being also 
very remarkable. 
The black oxide of iron contained in them cannot be thrown 
down by the addition of any of the hydrosulphurets, succinates, 
gallatcs, or any other tests for iron. 
This oxide always accompanies the Prussic acid, when the 
latter is transferred by stronger affinities from one base to 
another. 
For most of the facts just related, I am indebted to the ex- 
cellent paper of Proust, entitled “ Facts towards a History of 
the Prussiates.'' It appeared to me to be necessary to restate 
these facts in order to render clear the objects of this commu- 
nication, which are to reconcile with the general properties of 
other saline bodies the anomalies which the triple prussiates 
present ; to simplify the received opinion respecting their 
nature, and to make known some new acids which I have dis- 
covered. 
In endeavouring to accomplish these objects, I shall first 
state my opinion of the nature of the triple prussiates as they 
are called, and afterwards support it by experiments. 
I consider the salts termed triple prussiates as binary com- 
