termed triple Prus slates, 52 p 
pounds of an acid with a single base ; as salts which do not 
contain any Prussic acid, nor any oxide of iron as a base, al- 
though both these substances may be obtained from them by 
a decomposition of their acid. 
The first experiment which I shall adduce in support of the 
above opinion is one with the Voltaic battery; it appeared to 
me that this instrument would shew whether the oxide of iron 
in the triple prussiates existed in them as a base, or as an 
element of a peculiar acid by attracting it to the negative pole 
in the former, and to the positive pole in the latter case. I 
therefore exposed a solution of triple prussiate of soda to the 
agency of a small battery of fifty pair of double plates of one 
inch and a quarter square, kept in action for twenty hours, the 
solution was connected by platina wire with the negative pole, 
and by filaments of cotton with distilled water which com- 
municated by platina wire with the positive pole. Thus cir- 
cumstanced the triple prussiate of soda was decomposed, its 
acid (consisting of the elements of prussic acid and black 
oxide of iron ) was carried over to the positive pole ; here, 
meeting with oxygen from the decomposing water, it under- 
went a farther change by which it was converted into Prussic 
acid which was partly volatilized, and into blue triple prussiate 
of iron which formed there in abundance ; the liquid at the 
negative pole after this process contained only soda with a 
trace of undecomposed triple prussiate. In this experiment I 
consider the circumstance of the black oxide of iron being 
carried over to the positive pole as a proof that it went there 
as an element of an acid, for as a base it must have remained 
at the negative pole. 
I have repeated the above experiment with only the variation 
