HISTORY OF PRUS5IATES. 95? 



surely not more surprising than in the other; and, if we slate gives black 

 obtain red oxide by applying alkalis to a blue prussiate, on precipitated 

 the contrary we obtain black oxide from a white prussiate. 

 But these differences, which might be inferred from theory, 

 agree perfectly with those exhibited by the red and green 

 sulphates under similar circumstances. 



In my first paper I directed to pour the prussiate of pot- Caution. 

 ash on the sulphate in a phial, to avoid as much as possible 

 the admixture of air; but this succeeded imperfectly; first 

 because cold liquors always have air in them, and secondly 

 because I had not thought of sulphuretted hidrogen to free 

 them from it. I did not then know how it acted with re- 

 spect to these salts. 



If for instance a solution of green sulphate be diluted Excess of acids 



with three or four times its bulk of sulphuric or muriatic d ° not change 



r the white prus- 



acid, the excess of these acids makes no alteration in the siate to the blue 



result. As the white prussiate wants colour only from de- as th f ? d . Q not 



1 supply the 



feet of oxigen, it may be supposed such an addition is not necessary exi? 



calculated to impart it. These concentrated acids may alter S en> 



the whiteness of the prussiate indeed, but they can neve* 



bring it to a complete blue. 



Muriatic acid boiled on white prussiate is equally inef- 

 fectual. 



Not that this boiling acid is without action on the white Action of mu« 

 prussiate ; for I have observed, that there is some white [J atic aQld oa 

 prussiate destroyed, prussic gas evolved, and black oxide 

 found in solution. The little Prussian blue, that is formed 

 by the introduction of air, during the interval of these 

 mixtures, predominates over the white, and changes its co* - 

 lour to a greenish. 



The blue prussiate boiled with the same acid likewise gives and on the Hue 

 out prussic gas, and parts with red oxide, but less of it is P russiate 

 destroyed than of the white prussiate. From these facts we 

 may infer, that the muriatic acid, assisted by heat, is capa- 

 ble, in strictness, of decomposing prussiates, and assuming 

 jts rights of a stronger acid over the prussic ; which would • . 

 not be at all surprising, but at least I believe it would re« 

 quire considerable time, 



Prussktf* 



