1818.] Triple Prussiate of Potash. 105 



only the first of a series of more complicated inflammable gases 

 that will be hereafter discovered. 



The evolution of hydrogureted carbonic oxide by the action 

 sulphuric acid on triple prussiate K>{ potash is boih a c 

 unexpected fact. It renders Mr. Porrett's opinion hat 

 is a constituent of ferrureted chyazic acid exceedii 

 for there is no other, source of the hydrogen exce] t 

 with which the sulphuric acid was united. A gas ev.jlvt-; : . 

 triple prussiate of potash containing oxygen was altu^,. ther 

 unexpected, as the ferrureted chyazic acid seems destitute of 

 that principle altogether. The oxygen was obviously derived 

 from the sulphuric acid. This is clearly shown by the evolution 

 of the sulphurous acid which accompanied the hydrogureted 

 carbonic oxide. But the conversion of carbon into carbonic 

 oxide, and the union of this carbonic oxide with hydrogen, ha.e 

 never been observed in any other action of bodies containing 

 carbon or sulphuric acid. If this gas were to indicate the pro- 

 portion of carbon and hydrogen, which exist m ferrur. ted 

 chyazic acid, it would follow that they are to each other as three 

 atoms to one atom ; but as the whole acid is not decomposed, 

 we can draw no conclusion. What becomes of the azote which 

 is undoubtedly a constituent of ferrureted chyazic acid ? It is 

 obvious that the whole action of the sulphuric acid is not confined 

 to the carbon. It acts also on the iron, converting it into per- 

 oxide, as is evident from the prussian blue formed, and from 

 the persulphate of iron found in the retort. 



3. The action of nitric acid upon the triple prussiate of potash 

 varies so much with the strength and the proportion of acid 

 employed, and the degree of heat applied, that I have hitherto 

 but imperfectly studied the phenomena. My chief object was 

 the analysis of the salt, and I found nitric acid a most useful 

 reagent for that purpose. But it may be worth while to tran- 

 scribe some of the most striking observations which I noted 

 down. 



When triple prussiate of potash is mixed with about twice its 

 weight of concentrated nitric acid, it becomes immediately of a 

 light blue colour, indicating the sudden formation of a portion 

 of prussian bl.ie. Heat is evolved, and gas extricated in great 

 abundance. In a few minutes the extrication of gas stops, and 

 the whole of the salt is dissolved in the acid, constituting an 

 opaque liquid of a veiy dark brown colour. I kept this liquid 

 for more than a week without perceiving any alteration in it. 

 Ammonia renders its colour much lighter, and occasions a dark 

 precipitate, which, when well washed and dried, is a black, 

 tasteless powder, composed entirely of a mixture of prussian 

 blue and peroxide of iron ; for muriatic acid by digestion on it 

 acquires a yellow colour, and holds peroxide of iron in solution, 

 wink a portion of prussian blue remains undissolved. 



If heat be applied to the dark-coloured liquid, consisting of the 



