446 Count Le Maistre's Memoir or? [Dec. 



heat in order not to decompose the pmssiate of alumina, and 

 when the tint appeared to me equal through the whole mass, I 

 diluted it with boiling water. The prussiate, which was of a light 

 and dirty blue, immediately assumes a tine colour, and forms a 

 copious precipitate similar to prussiate of iron ; but which seems 

 somewhat soluble in water, to which it gives a greenish tint. 



As alumina has been long employed by the makers of prussian 

 blue along with prussiate of potash without any such combina- 

 tion being observed, I repeated the same experiment several 

 times to be certain of its accuracy, and I likewise made another 

 experiment which appeared to me conclusive. 



I precipitated the alumina from the sulphate by means of 

 carbonate of potash, I washed the earth on a filter, and dissolved 

 it, while yet in a gelatinous state, in muriatic acid. I heated the 

 solution which was very acid till it boiled, and then threw into 

 it boiling hot prussiate of potash. The effect was the same as 

 if it had been poured into a solution of protosulphate of iron. 

 Instantly a very fine green colour was developed, Avhich in two 

 days was changed into an intense and perfect blue. We have 

 seen that sulphate of alumina exhibits different phenomena, 

 which is doubtless the reason why this compound has never 

 been observed in the prussian blue manufactories. 



Alumina then has the property of forming a blue combination 

 with prussic acid, but only at a temperature not lower than 212°. 



XIV. Prussiate of Silica. 



To form this prussiate, I pounded in a glass mortar 50 gr. of 

 white glass from a barometer tube with 15()gr. of calcined potash. 

 I put the mixture into a covered crucible, and kept it red hot 

 for an hour. A frit was formed, which was almost completely 

 soluble in muriatic acid. I filtered the transparent and colour- 

 less solution, and raised it to a boiling temperature. I then 

 added 40 gr. of prussiate of potash, which gave a deep-green 

 colour to the liquid. After eight days exposure to the air, it 

 became a blue prussiate. 



The same process performed with pulverized quartz, prepared 

 for porcelain, gave the "same result. The prussiate of silica i* 

 blacker and less beautiful than prussiate of alumina. 



XV. Prussiate of Carbonate of Lime. 



Some salts, insoluble, or scarcely soluble in water, form like- 

 wise blue combinations with prussic acid without undergoing 

 decomposition. 



I boiled water containing carbonate of lime diffused through 

 it, and mixed with it a liquid containing prussiate of potash with 

 an excess of muriatic acid. The'prussic acid immediately united 

 with the carbonate, and the prussiate formed became" bluish- 

 black after some days exposure to the air. 



It was insoluble, in cold muriatic acid. Concentrated sul- 



