$$ tflSTOEY OF PRUSSIATE*. 



Prussiate ef Potash and Acids. 

 The crystal- Let weak sulphuric acid or muriatic be heated in a maf- 



treated^Tth * rass ,v ' t * 1 cr y sta ' s °f prussiate of potash. When ebullition 

 acids. commences, gas escapes, and may be received under a jar 



over mercury, or burned by applying to it a lighted candle. 

 The flame will be variegated with red, violet, and yellow *, 

 and during the extrication of the gas the liquor will be thick- 

 ened by the production of a white precipitate, which changes 

 to a blueish. When all the gas is evolved, throw the mix- 

 ture into boiling water, brighten it with oxigenized muriatic 

 It affords -34 or acid, wash, and dry the product in a capsule. Four ex - 

 bl ssian periments, made at different times, afforded me thirty-four 



or thirty-five parts of complete blue from a hundred of the 

 triple prussiate. 



' I proceed to the consequences : 

 Prussian blue A hundred parts of Prussian blue, without alum, yield 

 contains -54 or n f ty _ flve of ml oxido bv com bustion. The same blue, de- 



55 of red oxide J 4 7 



of iron. stroyed by nitric acid, gives fifty-four. It cannot be ques- 



tioned therefore, that Prussian blue contains fifty-four or 

 The ptussiate fifty-five hundredths of red oxide. From these data thirty- 

 asatesT'adds ^ ve P arts °^ blue ou g nt to produce about seventeen of black 

 19 per cent to oxide, or nineteen of red. Hence it follows, that, when 

 thrown d w * ron was f° rmer ty separated from a solution by prussiate of 

 potash, this salt added to the product the nineteen hun- 

 dredths of red oxide arising from its own decomposition ; 

 but the addition was still greater, when a simple alkaline 

 lixivium of Prussian blue was used instead of the crystal- 

 lized prussiate. The reason of this we shall see presently. 

 Prussian bine When Prussian blue is treated with a common lixivium of 

 common not- P°tash, part of the alkaline carbonate loads itself with 

 a *h. i red oxide ; and the result is a solution answering to Stahl's 

 martial tincture, of which pure potash is insusceptible. — 

 This solution, which may be prepared likewise by adding a 

 few drops of nitrate of iron to a solution of carbonate of 

 I. potash, will not occasion the least change in prussiate of 



potash, even by standing together. It is the same ferrugi- 

 nous carbonate, which, as I have said, is found in the 

 mother-water. In effect, if an acid be added to the mixture 

 of these salts, a perfect blue is precipitated, because the 



