434 COMPOUND SALTS 



to approach to a spherical form. The taste was 

 astringent, sweetish, and acid. The salt red- 

 dened vegetable blues, and underwent no sensi- 

 ble alteration from exposure to the air. It dis- 

 solved in water, with the exception of a very 

 small flocky sediment too insignificant to be 

 weighed, and doubtless consisting of some acci- 

 dental impurity. The solution had a yellow co- 

 lour, and was never transparent even though 

 passed through the filter. 



I found that 23*25 grains of this salt were just 

 decomposed by 26*5 grains of chloride of barium, 

 showing that it contained just 10 grains of sul- 

 phuric acid. From the same weight of the salt 

 I got very nearly 5 grains of peroxide of iron, 

 and 11 grains of sulphate of potash. Hence, 

 the constituents are 



1 atom persulphate of iron 1 



1 atom sulphate of potash 1 1 



2 atoms water 2-25 



23-25 



This is the only persalt of iron which I have ex- 

 amined, in which an atom of the peroxide is 

 combined with an atom of iron, 

 i- 7. Potash-sulphate of nickel. This salt crys- 

 nickci. tallizes in rhomboids having a fine emerald co- 

 lour. Its taste is sweet, with an impression of 

 bitterness, and it is not altered by exposure to 



