OF IRON. 329 



of the edges of the prism, or eight-sided from 

 the truncature of all the edges. The taste is as- 

 tringent and acid, and the crystals redden vege- 

 table blues very powerfully. They deliquesce 

 rapidly when exposed to the air ; when heated, 

 they melt in their water of crystallization, and 

 the liquid has a deep yellowish red colour. The 

 rapidity with which these crystals absorb water 

 makes it difficult to analyze them with perfect 

 accuracy. 



I found that 50 grains of them, when gradually 

 evaporated to dryness and finally exposed to a 

 red heat, leave very nearly 10 grains of peroxide 

 of iron. 



24'125 grains of the crystals were dissolved in 

 water, and the solution mixed with a solution of 

 10'125 grains of anhydrous carbonate of soda. 

 When the iron had subsided and the carbonic 

 acid had been allowed time to dissipate, the re- 

 sidual liquid was found to have the property of 

 giving a slightly purple colour to cudbear paper ; 

 but when one drop of muriatic acid was added 

 this property was destroyed, and the liquid red- 

 dened litmus paper. Hence, I conceive that the 

 acid in 24*125 grains of the salt is just neutraliz- 

 ed by the soda in 10' 125 grains of anhydrous 

 carbonate of soda. But 1O125 carbonate of 

 soda is equivalent to 1 \ atom of soda ; conse- 

 quently, 24-125 of the salt must contain li atom 

 of nitric acid. The water absorbed by the crys- 



