170 INSECTICIDES, FUNGICIPES, AND WEED KILLERS. 



— By precipitating green vitriol by an alkaline sulphide. It forms a 

 black gelatinous powder. 



Properties. — Insoluble in water. Readily oxidizes in air. 



Use. — Galloway tried against the rust of oats and wheat a bouillie 

 of sulphide of iron obtained by precipitating 28 lb. of green vitriol by 

 24 lb. of liver of sulphur and thinning down the whole to 100 gallons. 

 In spite of four sprayings, 6, 16, 20 June and 5 July, the result 

 was negative, as might have been foreseen, looking to the insolubility of 

 iron sulphide in atmospheric agents. Fairchild used this bouillie 

 against Entomosporiicm maculatum (spots of the leaf of the pear-tree, 

 leaf scald) and Phyllosticta s2)hcBr ops idea, E. and E. (spots of the leaf 

 of the chestnut). The experiments showed that it was not capable 

 of circumscribing or preventing these diseases, but that it caused 

 serious damage to the leaves of the plants treated. 



67. Iron Chloride, Fe._,CI^5H^0. — Preparation. — By dissolving 

 iron in aqua regia or by passing a current of chlorine into a solution 

 of protochloride of iron (ferrous chloride). The solution concentrated 

 by boiling yields on cooling orange red crystals of ferric chloride. 



Properties. — Very soluble in water. Its solutions coagulate 

 blood and act as hemostats in medicine. 



Use. — Galloway found a 1 per cent solution sprayed every ten days 

 on wheat fields preserved them against rust. The treated plot showed 

 no rust. The check plot showed twelve plants attacked. This action, 

 which greatly resembles the action of soluble salts of copper, is ap- 

 parently only due to the exceptional vigour of the cereals due to this 

 treatment. Moreover, Hitchcock and Carleton have shown that a 

 1 per cent solution of perchloride of iron can only interfere slightly 

 with the vitality of the spores of Puccinia coronata, Corda (crown rust 

 of oats), and Wuthrich has proved that it requires a 10 per cent solu- 

 tion of perchloride of iron to kill the uredospores of Puccinia grcmiinis, 

 Pers. (linear rust). At the same strength as the persulphate of iron, 

 ferric chloride is directly assimilable by the leaf and acts as a powerful 

 stimulant of the vital functions of the plant. As a tonic, perchloride 

 of iron may be of use in the struggle against the diseases of plants, 

 but it cannot be ranked as an anticryptogamic substance capable of 

 killing the spores of fungi. 



Entomos2)orium maculatum (spots of the leaf of the pear), Phyl- 

 losticta spliceropsidea, E. and E. (disease of the leaf of the chestnut). — 

 Fairchild used to combat these two fungi a mixture of 1 per cent of 

 ferric chloride, 1 per cent of carbolic acid, even 0-5 per cent of each of 

 these substances. Without any action on the development of these 

 diseases, the two mixtures seriously scorched the leaves. 



Chlorosis. — Stevignon made comparative trials with perchloride of 

 iron and green vitriol, and found that the action of the perchloride was 

 much more rapid than that of the sulphate. He obtained the best 

 results by making incisions in the bark of the stocks, and coating the 

 wounds with a 40 per cent solution of perchloride of iron ; fifteen days 

 after treatment the chlorotic vines were quite green. Comparative 

 trials with hydrochloric acid itself have shown that it is the iron which 

 is the active element and not the hydrochloric acid. 



