1819.] Mr. Porrett on Ferro-chyazate of Potash, fyc. 295 



Article X. 



On Ferro-chyazate of Potash, and on the Atomic. Weight for Iron. 



By R. Porrett, Jun. 



In a paper of mine published in vol. xii. of the Annals of Phi- 

 losophy for 1818, p. 214, on the Triple Prussiate of Potash, I 

 drew a comparison between my analysis of this salt made in 

 1814 and that made by Dr. Thomson, which had just appeared, 

 and after remarking, as that acute chemist had done, that the 

 results did not accord with the atomic theory, I related an expe- 

 riment I had made by decomposing the triple prussiate with 

 tartaric acid, which seemed to prove ttiat both had overrated the 

 quantity of potash in that salt, and that when this was corrected, 

 the number for its acid constituent would be represented on the 

 scale of equivalents by 85*9. 1 showed also that a nearly similar 

 number, namely 84*7, resulted from my analysis of ferro-chyazate 

 of barytes (after rectifying a mistake in the quantity of water 

 which I had attributed "to that salt) ; and that if we considered 

 the ferro-chyazic acid as composed of 



4 atoms carbon 30*16 



1 atom azote 17*54 



1 atom iron 34*50 



2 atoms hydrogen 2*64 



84*84 



the number representing its atomic constitution would then 

 agree very well with the equivalent number derived from the two 

 analyses above-mentioned. 1, therefore, proposed this view of 

 its nature as a probable explanation of the discrepancies between 

 the former experimental results, and those deducible from the 

 application of the atomic theory. But this explanation, hitherto 

 only probable, assumed all the appearance of a well-established 

 fact ; when upon carefully collecting and examining the gases 

 produced from the combustion of ferro-chyazic acid, I actually 

 obtained carbonic acid and azote gases in the proportions of four 

 volumes of the former to one volume of the latter gas ; and in 

 quantities which, as nearly as could be expected, were the same 

 as calculation indicated. 



After this I entertained no doubt but that I had given the exact 

 composition of ferro-chyazic acid, and also of its salts, with base 

 of potash and of barytes ; and was very much surprised when I 

 learned that Mr. R. Phillips had ascertained that it did not 

 contain so much iron as I had assigned to it. This circumstance 

 Mr. Phillips obligingly requested a mutual friend to communicate 

 to me. 



My attention being thus again called to the subject, I soon 



