432 COMPOUND SALTS 



After the sulphate of barytes had subsided, the 

 residual liquid was neither affected by sulphate 

 of soda nor muriate of barytes. Consequently, 

 26'125 grains of the salt contain 10 grains of 

 sulphuric acid. Hence, the constituents of the 

 salt are 



1 atom protosulphate of iron 9*5 



1 atom sulphate of potash . 1 1 



5 atoms water . . 5*625 



26-125 



Potash-per- 5. Potasli-Dersesquisulphate of iron. This salt 



sesquisul- 



phate of may be obtained by mixing together solutions of 



iron. 11 / 111 r i- 



persulphate or iron and sulphate of potash in 

 the requisite proportions, and crystallizing under 

 the vacuum of the air pump along with sulphu- 

 ric acid to absorb the vapour. The crystals are 

 transparent and colourless, and have the regular 

 octahedral form like alum. The taste is astrin- 

 gent, sour, and sweetish, similar to that of alum, 

 but harsher. The salt dissolves in water, and 

 the liquid containing it has a brownish red co- 

 lour. I have never succeeded in getting crys- 

 tals after once dissolving this salt in water, The 

 crystals redden vegetable blues, and are not al- 

 tered by exposure to the air. 



I found by a process quite similar to what has 

 been so often stated, that 64-125 grains of these 

 crystals were just decomposed by 53 grains 

 (13-25 x 4) of chloride of barium, and conse- 



