ACTION OF CONCENTRATED SULPHURIC ACID ON IRON. 63 



error. Some crystals of FeS0 4 + 7 H 2 were then treated 

 with concentrated sulphuric acid and washed with alcohol 

 in a similar manner, to see if one molecule of water was 

 retained as found above. The analysis showed this to be 

 the case. 



This was previously noticed by Scott 1 who worked on 

 mixed sulphates of copper and iron. He found that FeS0 4 

 + H 2 is easily prepared in the following manner: — a 

 saturated solution of the salt (hydrated, 7 H 3 0) is prepared 

 in the cold, and an equal volume of concentrated sulphuric 

 acid added. A precipitate is obtained and washed two or 

 three times with H 2 S0 4 diluted with its *own volume of 

 water, then with absolute alcohol, then with a mixture of 

 absolute alcohol and dry ether, and finally with dry ether, 

 and dried over concentrated H2SO4 in an evacuated desic- 

 cator. Roscoe and Schorlemmer state that ferrous sulphate 

 is insoluble in concentrated sulphuric acid and absolute 

 alcohol, but dissolves slightly in dilute alcohol. Hence, 

 sulphuric acid and alcohol precipitate solutions of sulphate, 

 the precipitate containing varying quantities of water of 

 crystallisation according to the amount of precipitant and 

 concentration of the solution. 



This previous work is in accordance with the author's 

 analysis of the powder obtained from FeS0 4 + 7 H 2 by 

 treatment with sulphuric acid and alcohol, and a comparison 

 between this analysis and that of the sediment obtained 

 directly from the iron by action of H 2 S0 4 indicates the 

 close relation between the two. 



Sediment from Prepared from Calculated for 



Experiment. FeS0 4 + 7 H 2 0. FeS0 4 + H 2 0. 



Fe 32*8 32*6 32*88 



SO* 57*7 56*4 56*51 



The conclusion drawn was that anhydrous ferrous sul- 

 phate was formed by action of concentrated sulphuric acid 



1 Jour. Chem. Soc, 1897, p. 564. 



