100 HISTORY OF PllUSSIATES. 



by the impression of the air; but it certainly Mill not be 

 the same with the black oxide, which passes into the Prus- 

 sian blue jointly with the acid. This oxide will not lose 

 the quality of being at a minimum, which it had in the 

 prussiate of potash ; that is to say, if, during the exposure 

 to air, the basis of the green sulphate, and consequently 

 that of the white prussiate, raise its proportion of oxigen 

 from 28 to 48 per cent, the black oxide, the inseparable 

 companion of the prussic acid, will not participate in this 

 super-oxidation, but will invariably keep to its 28 per 

 cent. 

 .Wither the air, Not only the atmosphere, which so easily raises the 



jior boiling bases of the sulphat, muriate, and white prussiate to their 

 nitric acid, nor . „ . . . , ,. , ,, , 



oxigenized maximum, loses all its activity when applied to the black 

 muriatic, oxide ox j < } e j n q ues tion ; but neither boiling nitric acid, nor the 



it more, ... . . . . • , . mi 



except as these oxigenized muriatic, can increase its oxidation. Ihcse 

 acids destroy acids are capable indeed of destroying prussian blue, and 

 the blue itself. ,..„.* , ., , 1 , ui 



even reducing it to red oxide; but as long as any blue re- 

 mains to be destroyed, this will to the last retain its black 

 oxide in all its primitive integrity. 

 Red oxide of If red oxide be treated with prussic acid, no kind of 



iron will not combination will take place between them. This is agree- 



combine with ■ 



prussic acid, able to the observation of Scheele. But if we employ 



but blaek will. b] ac k oxide, we shall obtain a greenish prussiate, which 

 will be rendered perfectly blue by the action of the air. 

 Black oxide therefore enters into the composition of prus- 

 sian blue. If this oxide were unnecessary, or if the red 

 oxide might serve exclusively as the base of prussian blue, 

 it does not appear why this oxide, brought into contact 

 with the prussic acid, and even its solution mixed with 

 simple prussiate of potash, should not afford prussian 

 blue. 



\.\ ity of the I have remarked above, that the affinity of the prussic 



prussic acid for ac ; d for guch a dosc of b j ack os jj ag adapts j fc to the 

 a '.riven propor- _ . ' 



tion ofWack production of the triple prussiate. may be sufficiently 



oxide, very powerful, to protect it from the common fate of oxides 

 strong. * . 



combined with acids in general : and in fact it appears to 



me, tlmt this inference may be drawn from the following 



experiments. 



, • n-r>: l Pour hidrosulphuret of potash into a phial on prussian 



blue 



