19 



cent, and was detrimental when 4 per cent was reached. The 

 increase varied with different crops, from 5 per cent to 139 per 

 cent. 



Cazeneuve and Nicolle 1 studied the solvent action of ferrous 

 sulphate on some of the phosphatic fertilizers in common use, 

 namely, slag, mineral phosphate, bones, superphosphate, and di- 

 calcium phosphate. After eight days the first three had suffered 

 no change in the amount of phosphoric acid soluble in acetic acid 

 and ammonium citrate. With superphosphate half of the water 

 soluble had become reverted. With the di-calcium phosphate, 

 the phosphoric acid soluble in acetic acid and ammonium citrate 

 had increased, but the change was not to the water soluble form. 



The action of ferrous sulphate on crops was investigated by 

 Boiret and Paturel 2 . Seedlings of peas and oats were used in 

 water culture experiments. Even with very dilute solutions, the 

 plants were poisoned, owing to the formation of free sulphuric 

 acid. Iron citrate and citric acid had the same effect. Tests 

 were then made with soils containing known quantities of lime. 

 The sulphate was injurious except when there was present a suf- 

 ficient amount of lime to neutralize the free acid formed. Analysis 

 of the crops showed that ferrous sulphate had no effect on the 

 amount of phosphoric acid in the product. In these experiments 

 the sulphate was not used in conjunction with other fertilizers, as 

 in the work of Griffiths already quoted. 



1 Chem. Centr., IV, (2) 1892, 121. 



2 Ann. Agron., 18, 418. 



