Materials for a History of the Prussiates. 49 



the following experiment : I distilled the following mix- 

 ture i charcoal of blood, six drachms; argil and sea salt, 

 each two drachms; but the produce in sal ammoniac was 

 much below my expectations. 



All the vegetable charcoals azotized are proper for making 

 Prussian blue. Thus those of gluten, of chick peas, indigo, 

 and of pit-coal, have yielded dyeing lixiviums, sometimes 

 mixed with hydro-sulphuret : those of sugar-cane and of 

 milk do not give any indication of blue. 



Charcoal of chesnuts and of ^rush-wood, which are 

 preferred at the foundcries to any other kind, because they 

 have the advantage of being extinguished the moment the 

 bellows cease, do not owe this to a2ote, for their Irxiviums 

 do not contain any thing prussic in them. 



Cream of tartar made red-hot gives a lixivium, which 

 does not give the least blue : nor did two parts of cream of 

 tartar and one of sal ammoniac ; but one part of sal am- 

 moniac with four of cream of tartar yield a lixivium which 

 contains simple prussiate. It gives blue with the green sul- 

 phate of commerce. Cream of tartar and nitre of soda, 

 nothing. 



This result proves clearly that it is by the azote alone that 

 animal are preferable to vegetable charcoals. It also results 

 from this, that if we can at any time discover some azotized 

 combination, more capable of supporting a strong heat than 

 the ammoniacal salts, we might succeed in forming the 

 prussic acid in a manner perhaps less laborious than by ihe 

 animal charcoals. 



Examination of the Lixiviums. — By distillation they give 

 continually prussic acid and ammonia: we have seen the 

 origin of this a little higher. 



They contain carbonate of potash in a great quantity. 



Simple prussiate of potash. 



Triple ditto. 



Sulphate of potash. 



Phosphate of lime. 



Sulphur. 



They deposit phosphate of lime in proportion as we eva- 

 porate them : I know not how it is formed, 



Vol. 33. No. 129. Jan. 1809* D If 



