IRON SULPHIDE. 169 



of iron be not used. Whilst 1 per cent solutions of ferrous and ferric 

 salts produce a stimulating effect on the plant, it requires 3-15 per 

 cent of hydrated oxide of iron to produce the same effect, and it is 

 necessary to apply these bouillies in sprayings several times a year. 

 Lagarrique recommends to apply them every fifteen days. Several 

 scientific observers have imagined that the stimulating effect of copper 

 bouillies was to be attributed to the sulphate of iron present in greater 

 or less amount in commercial sulphate of copper. In their opinion, 

 pure copper sulphate free from iron would have no salutary effect on 

 the plant and could not be absorbed by it without injuring its health. 

 The mixed bouillies of sulphate of iron and sulphate of copper re- 

 commended to accentuate the stimulating effect of bouillie bordelaise 

 are: — 



Pellegrini's, 1 lb. of blue vitriol, 1 lb. of green vitriol, 1 lb. of quick- 

 lime in 10 gallons of water. Aderhold's, 19 lb. of blue vitriol, 1 lb. of 

 green vitriol, 20 lb. of quicklime in 100 gallons of water. Sorauer's, 

 19^ lb. of blue vitriol, ^ lb. of green vitriol, 20 lb. of lime in 100 

 gallons. Goucdenovic, who examined the action of these bouillies 

 compared with those of pure sulphate of copper, found they were in 

 no way superior as stimulants. One cannot understand in fact how 

 a copper bouillie containing only 0"l-0"05 per cent green vitriol as 

 hydrated oxide of iron can produce any stimulating effect when it is 

 necessary to use 3 per cent of this oxide to produce the same effect 

 with a ferric bouillie. 



Action of Ferric Bouillies on Fungi. — The hydrated oxide of 

 iron has no pronounced toxic action on the spores of fungi, and cannot 

 in any case replace the hydrated oxide of copper in the struggle 

 against cryptogamic disease. Although green vitriol be ten times less 

 toxic for plants and fungi than blue vitriol, these relations do not exist 

 between the corresponding iron and copper oxides. The numerous 

 experiments to replace the costly cupric bouillie by bouillies with a 

 hydrated oxide of iron base have given no result in the struggle against 

 plant diseases due to parasitic fungi. 



PhytophtJiora infestans, De By. (potato disease). — Iron bouillies 

 have been more especially tried against this disease as substitutes for 

 bouilUe bordelaise. Giltay's experiments with a bouillie of 1 per cent 

 green vitriol and \ per cent of lime gave negative results. Sempotowsky 

 tried stronger bouillies, but they had no more effect in diminishing or 

 preventing the potato disease than the 1 per cent solution. Steglich 

 also points out the bad effects oa potatoes by treatment with iron 

 bouillies containing 2-4 per cent of sulphate of iron. 



Gloeosporium aitipelophagum, Sacc. (grape rot). — Pellegrini ob- 

 tained very good results in overcoming this disease with a bouillie 

 consisting of 1 lb. of blue vitriol, 1 lb. of green vitriol, and 1 lb. of lime 

 in 10 gallons of water. 



Entomosporium maculatum, Lev. (spots of the leaf of the pear- 

 tree, leaf scald). — Fairchild did not cure this disease by using a bouillie 

 consisting of 0-6 per cent of hydrated oxide of iron prepared by pre- 

 cipitating green vitriol by caustic potash. 



66. Sulphide of Iron (Ferrous Sulphide), FeS,. — Preparation. 



