FERROUS SULPHATE. 379 



Percentage of Specific gravity of 



crystallized salt. solution at 15. 



25 ... ... 1-1430 



30 .. ... 1-1738 



35 ... ... 1-2063 



40 1-2391 



The salt is insoluble in absolute alcohol. 



Iron sulphate is used in agriculture mainly as a fungicide, 

 occasionally as a disinfectant, as a manure,* and as a veteri- 

 nary medicine. 



In recent years it has been largely employed as a means of 

 destroying charlock and runch, being used as a spray in the 

 same manner as copper sulphate. The strength of the solu- 

 tion to be employed varies slightly with the age of the charlock 

 at the time of spraying. 



If the plants be treated when young, a 10% solution is 

 probably best, while for older plants a 15% solution will 

 generally be advisable ; in both cases the liquid should . be 

 sprayed at the rate of about 40 gallons per acre. Mixtures of 

 the finely-divided dry salt with marl, applied as a powder, 

 have been tried, but with little success. | As is the case with 

 copper sulphate, iron sulphate appears to have a stimulating 

 effect upon cereals, and many results, among others those 

 obtained in the experiments conducted under the supervision 

 of the Yorkshire College and the East and West Eidings Joint 

 Agricultural Council in 1899, seem to show that, even where 

 no charlock or runch may be present, the cereal crop is bene- 

 fited by spraying.]; 



For severe cases of fungoid diseases, in vines, &c., a strong 

 solution of ferrous sulphate to which about 1 % of free sul- 

 phuric acid has been added is said to be very effective. 



Ferrous sulphate, like copper sulphate, is a plant poison, 

 and its success as a fungicide (indeed, probably that of all 

 substances used in that capacity) is probably due to the fact 

 that the fungi are more susceptible to its action, because of 

 their thinner walls, than the higher plants. 



* v. p. 170. f Jahresbericht iiber Agricultur-Chemie 1901, 352 



\ This effect may be either a direct manurial one, an indirect one by promoting the 

 disintegration of the minerals in the soil, or by increasing the chlorophyll production, 

 or, lastly, be due to the destructive action of the salt upon fungoid pests. 



