114 Mr. R. Phillips on the Triple Pnissiate of Potash. 



water separated by heating them, on this view, arising from 

 the decomposition of hydrocyanic acid and the metallic ox- 

 ides, and the union of their hydrogen and oxygen ; or sup- 

 posing the crystallized salt to be a double cyanide containing 

 not merely the elements of water, but water of crystallization, 

 still water may be decomposed when the crystals are dissolved 

 in it, the hydrogen of the decomposed water uniting with the 

 cyanogen to form hydrocyanic acid, and the oxygen with the 

 metals giving rise to potash and protoxide of iron. 



Lastly, When cyanide of iron and potassium is dissolved in 

 water, and tartaric acid is added to the solution, water must 

 be decomposed either previously to, or on adding the acid, 

 for bitartrate of potash is precipitated ; and if the iron as well 

 as the potassium be also oxidized, we shall have oxygen as 

 well as hydrogen entering into the composition of ferrocyanic 

 acid ; and supposing that the three atoms of water expelled 

 from the triple prussiate by heat, do not previously exist as 

 such, but are formed during its action, the salt may be re- 

 garded as anhydrous ferrocyanate of potash, consisting of 



6 atoms carbon .... 36 



3 azote 42 



3 hydrogen ... 3 



1 atom oxygen 8 



1 iron 28 



117 = 1 atom ferrocyanic acid. 



2 atoms potash 96 



213 



Viewino- this as the constitution of the substance in ques- 

 tion, it is a diferrocyanate of potash, or composed of one atom 

 of acid and two atoms of base. 



I am perfecdy aware of the difficulty which attends the sup- 

 position that water is formed during the exposure of the cry- 

 stals of ferrocyanate of potash to heat ; but the question is one 

 of probabilities, and Berzelius* has well remarked, " qu'il est 

 impossible de decider si cette eau s'y trouve dans I'etat qui 

 lui est propre, ou si ses principes constituans y etaient em- 

 ployes a la formation du prussiate d'oxidule de fer." I am 

 at present engaged in the pi-osecution of experiments, by 

 which I hope to throw additional light on this part of the sub- 

 ject, and which, as far as I have proceeded, are confirmatory 

 of the opinions now expressed. 



• Chimiedu Fer, p. 180, 



XXVI. On 



