CHAPTEE XIII. 



COPPEE SULPHIDE— COPPER NITEATE— COPPER CHLORIDE— COPPEE 

 SULPHITE— COPPER SULPHATE (BLUE VITRIOL). 



86. Copper Sulphide, CuS. — Preparation. — (1) By passing a cur- 

 rent of sulphuretted hydrogen into a solution of a copper salt. The 

 black precipitate formed is filtered and washed with a solution of sul- 

 phuretted hydrogen. (2) By double decomposition of sulphate of copper 

 by the sulphide of an alkali or alkaline earth. 



Properties. — Copper sulphide is an amorphous black precipitate, 

 absolutely insoluble in water. In moist air it oxidizes and forms 

 sulphite and sulphate of copper. By heat it decomposes into basic 

 copper sulphide and sulphur. 



Use. — Copper sulphide has been recommended against oidium as 

 well as mildew, that is to say, to unite in a simple treatment both 

 sulphur and bouillie bordelaise. Copper sulphide, containing the 

 necessary elements to fight these two parasites, it was thought might 

 produce the desired effect. It was not so, however, and Viala's ex- 

 periments at the Montpelier school showed that copper sulphide 

 neither protects vines from mildew nor kills the oidium. Numerous 

 observers hold the same opinion as Viala and condemn mixtures 

 which form copper sulphide. In fact, the copper is so insoluble in 

 this sulphide derivative that this preparation no longer cedes to dew 

 or rain the indispensable amount of copper to prevent the germination 

 of the spores which have been transported by the wind, and the sulphur 

 in the sulphide no longer possesses the properties of sulphur. It is not 

 volatile, and cannot consequently act by its vapours. However, 

 copper sulphide may oxidize in the air and thus cede to the water on 

 the leaves a little soluble copper as copper sulphate. This, in fact, 

 occurs in moist countries, and it is one of the reasons why certain 

 experimenters found a protection in it against mildew equal to that of 

 bouillies. The special bouillies recommended by Fairchild, and after- 

 wards by Eabate, may perfectly combat oidium, but they have only an 

 imperfect action against mildew. Consisting of a mixture of 4 lb. of 

 copper sulphate and of 4 lb. of sodium polysulphide (liver of sulphur) in 

 100 gallons of water, in the first instance, and a mixture of copper 

 sulphate and lime sulphide in the second, they contain, along with 

 precipitated copper sulphide, sulphides, or polysulphides of sodium 

 or calcium, as well as precipitated sulphur, which have a well-deter- 

 mined action on oidium. 



Against Entomosporknii macidatmn (spots of the leaves of the pear) 

 Fairchild did not find h's bouillie superior to ordinary copper bouillies. 

 (199) 



