SO Materials for a History of the Vrussiales. 



If we saturate a portion of lixivium with sulphate of iron, 

 and examine the blue liquor formed by it, we discover phos- 

 phate of iron. This phosphate induced Westrumb to think- 

 that the prussic acid was phosphoric. 



Alcohol applied to concentrated lixiviums takes simple 

 prussiate from them ; but it appears difficult to purify them 

 by this means. The triple prussiate remains in the lixivium 

 with the carbonate. 



Of these two prussiates, one only can give Prussian blue 

 with solutions of red oxide ; namely, the triple prussiate, be- 

 cause it is provided with black oxide. The other cannot, 

 because it has not the black oxide: but it does so, and 

 becomes triple prussiate, as soon as we mix the lixiviums 

 with the sulphate of iron of commerce: and consequently, if 

 we use sulphate completely red, we shall have infinitely 

 less Prussian blue, because, the black oxide being wanting, it 

 could not become triple prussiate and give blue with this 

 sulphate. Two experiments will render this apparent. 



I divided a lixivium into two equal parts; one part was 

 precipitated with red sulphate, and the other with the green 

 sulphate of commerce. The excess of oxides being separated, 

 the blue of the second was in proportion to that of the first 

 as four to one. 



The first lixivium, when filtered, exhaled a strong smell 

 of almonds. I saturated it with potash, in order to fix once 

 more the free prussic acid : when tried afterwards with red 

 sulphate, it did not give one atom of blue; but with the 

 green sulphate it gave abundance. We may therefore con- 

 clude that, without the aid of black oxide, a carbonaceous 

 lixivium would not give with solution of red oxide the whole 

 of the blue which it might. From this would arise the Joss 

 that might be suffered of all the simple prussiate contained 

 in a lixivium if we only used a sulphate the oxide of which 

 was completely red •> and from this proceeded the mistake 

 into which 1 fell when I advised it. I did not reflect that, if 

 the green sulphate has the inconvenience of giving pale prus- 

 siate, the oxygen of the air soon remedies this defect ; but 

 it has the essential advantage of furnishing to the simple 

 prussiate the portion of black oxide which it requires in 



order 



