Foreign Literature and Science. 179 



alone give very little cyanogen. Second, it produces more 

 with potash, but the prussiate is not ferruginous. Third, 

 ammonia is then produced in great quantity. Four, the sub- 

 stitution of nitre for potash and the addition of clippings or 

 scales, (vattitures) increase the production of cyanogen, and 

 give a ferro-prussiate. The author has practised this pro- 

 cess for two years in the neighborhood of Paris. His meth- 

 od as he describes it is as follows. 



Blood, supposed dry, . - - 3 parts. 



Nitrate of potash, ... 1 part. 



Scales of iron, - - - - sV of the blood. 



After having coagulated the blood in a large copper ket- 

 tle the serum is pressed out and the clot returned to the ket- 

 tle, with the nitre and the iron. The humidity of the blood 

 is sufficient to liquefy the salt, so that the mixture becomes 

 uniform. It is then removed to an airy loft, where the de- 

 siccation is completed. The putrefaction of the blood is 

 prevented by the nitrate of potash. When completely dry 

 it is put into cast iron cylinders, arranged in a reverberatory 

 furnace similar to those used for ivory black. The cyhnders 

 are heated to dull red, or until smoke ceases to be disenga- 

 ged. The materials after being thoroughly cooled, are with- 

 drawn, and put into a wooden vat, with twelve or fifteen times 

 their weight of water, and left one hour. The fluid is then 

 filtered through a cloth and evaporated to the thirty-second 

 degree of Baume^'s areometer. On cooHng, a considerable 

 quantity of the bicarbonate of potash is produced, in well 

 formed crystals. The author has not been able to satisfy 

 himself with respect to the manner in which this bicarbonate 

 is formed at so high a temperature, since a portion appears 

 to be decomposed during the evaporation of the ley, at first, 

 but little alkaline, but which becomes very sensibly so, by a 

 prolonged evaporation. 



The same product is not obtained when the potash of 

 commerce is used. It is probable that the elements of 

 the nitric acid act an important and necessary part in this 

 operation. 



The solution which has furnished these crystals, contains 

 a little sub carbonate of potash and much cyanuret of ferru- 

 retted potassium. The liquor is contracted to 34. placed in 

 wooden vessels cased with lead. In the course of a few 

 days a greenish crystalline mass is obtained : these crystals 

 are re-dissolved in a fresh quantity of pure water, which 

 evaporated to 32 or 33, yield crystals anew.— -Ibid, 



