200 INSECTICIDES, FUXGICIDES, AND WEED KILLERS. 



Galloway, however, found it act better against rust ol' oats and summer 

 wheat. Plots treated on 6, 16, and 20 June, then on 5 July, were not 

 diseased, and yielded 10.} units of sound grain against 8.1 units in the 

 untreated plots, the plants of which were diseased. 



If sulphur be mixed with fat lime in the proportion of fat lime 

 260 lb., precipitated sulphur 260 lb., water 7 gallons, and the pro- 

 duct mixed with a copper salt in the following proportion, above mix- 

 ture 4 lb., copper sulphate 2 lb., water 10 gallons (Guillon's formula), 

 a bouillie is obtained which, used immediately after its preparation, 

 enables oidium and peronospora to be contended against simultane- 

 ously, because sulphur only acts very slowly on copper hydrate to 

 form copper sulphide. It is otherwise if a solution of copper sulphate 

 is mixed with soluble sulphides, or even if the sulphur is added to 

 alkaline bouillie ; these bouillies are blackened instantly by the copper 

 sulphide formed and are now merely copper sulphide bouillies, less 

 adherent and less active than bouillie bordelaise. 



87. Copper Nitrate, Cu(N0.,)o3H.,0.— Preparation.— By dis- 

 solving copper in dilute nitric acid and crystallizing the solution. 



Properties. — Soluble in water with the same anticryptogamic pro- 

 perties as copper sulphate. 



Use. — Hitchcock and Carleton tried the effect of a 1 per cent solu- 

 tion on the spores of different fungi. At that strength the spores of 

 rust {Puccinia coronata) were destroyed. Copper nitrate is regarded 

 as one of the best means of destroying weeds, and is used on the large 

 scale to destroy charlock. 



88. Copper Chloride, CuCl22H.^O. — Preparation. — By dissolv- 

 ing copper oxide in hydrochloric acid, or copper in aqua regia, and 

 evaporating the solutions. Copper chloride bouillies are prepared by 

 mixing 249 lb. of copper sulphate and 219 lb. of calcium chloride ; 

 sulphate of lime is precipitated and copper chloride goes into solution. 



Properties. — Copper chloride is soluble in water. It behaves like 

 copper sulphate as regards its corrosive action on leaves and its anti- 

 cryptogamic effects. Its molecular weight being 170, that of copper 

 sulphate 249, and the action of copper salts being in inverse ratio to their 

 molecular weight, the chloride will, in doses of equal weight, be more 

 active, and should be used in smaller doses than copper sulphate. 

 Galloway has, however, remarked that dilute solutions of copper 

 chloride do not attack the leaves of plants like those of copper sulphate ; 

 it is necessary to attribute this difference to the different nature of the 

 hydrochloric acid and sulphuric acid which form these two salts, the 

 first is volatile, the second is not so. 



Galloway used against the black rot of the vine a mixture, consist- 

 ing of 7^ oz. of copper sulphate, 4 oz. of calcium chloride, in 624 

 gallons of water. This bouillie much diminished the black rot. The 

 vines sprayed six times showed 98'1 per cent of healthy grapes against 

 41-61 on the untreated stocks. On the other hand, being very dilute 

 it does not attack the leaves at all. A 1 per cent solution prevents 

 the germination of the uredospores of Puccinia coronata, Corda (rust 

 of oats), (Hitchcock and Carleton). Along with pure solutions of 

 copper chloride there are used in America, with little success it is true, 



