HISTORY OF PRUSSIATES. ggj 



not redden litmus ; it does not dissolve in water, the proper 

 menstruum of acids, so well as in alcohol ; and it is even de- 

 composed in it spontaneously without access of air. With 

 alkalis it forms combinations so imperfect, that we find in 

 them the specific properties of their component parts scarcely 

 altered; and the weakest of all acids, the carbonic, is capa- 

 ble of decomposing them. In short, its combustibility, taste, 

 smell, generation amid volatile oils and kernels, and quality oreana °- 



'; . . ' j 1 J gous to o^s and 



of keeping in alcohol, form an assemblage of properties, by inflammables. 



which it approaches much nearer to oily and inflammable 



productions than to saline substances. 



ftv * " ' i i i m i- • i- -• Yet toward ox- 



JLhe prussic acid, however, notwithstanding its little sa- j t ie of mercury 



line energy, attacks the oxide of mercury at a maximum with itactsasapow* 

 great advantage; and with this oxide it furnishes a saline 

 combination so strongly characterized in its qualities, that 

 we are obliged to acknowledge it acts under certain circum- 

 stances as one of the most powerful of acids. In fact, the p U5s iate of 

 prussiate of mercury wants nothing to entitle it to rank with Kiercui y« 

 the most perfect metallic salts; and what may perhaps be 

 deemed astonishing is, to see it refuse to combine with the 

 oxide at a minimum; yet, from the effect of concurrent affi- 

 nities, of which there are other examples, it raises it to the 

 state of an oxide at a maximum, separating one portion of 

 the metal, to form a prussiate with the other. 



Prussic acid has no action on the red oxide of iron; but it Actionofprns- 

 very readily attacks the black oxide, and produces with it sic acid on iron. 

 white prussiate. It is true this prussiate is not strictly white, 

 on account of the difficulty of preparing a precipitate with 

 the green sulphate totally free from a surplus of oxide; 

 and accordingly it is always greenish : but as it becomes a 

 perfect prussian blue by drying, there can be no doubt, that 

 the prussic acid and the base of green sulphate, if not af- 

 fected by contingent circumstances, would furnish a prus- 

 siate as white as that which we obtain in a more easy manner. 



Prussian blue is not a single compound, as had been sup- p rus i san D j ue 

 posed. This the following observation is sufficient to show, not a single 

 It is known, that the base of this blue is the red oxide of com P oun ■ 

 iron : but, if this oxide alone were sufficient to make prussian 

 blue, why is not this blue afforded by prussic acid and red 

 oxide? and why do not the alkaline prussiates produce it 



with 



