POTASSIUM XANTHOGENATE. 129 



tons per acre). After spreading it would suffice to hoe the ground so 

 as to mix it with the earth and protect it from contact with the air 

 which would decompose it. From Laugier's experiments it would 

 appear possihle without hurting the vine gradually to extinguish the 

 hotbeds of phylloxera infection, by aid of repeated mixed treatments 

 of sulphocarboaate of potassium and carbon disulphide, applied op- 

 portunely and in suitable doses. This process, much used in Switzer- 

 land and Italy, appears to leave nothing to be desired. 



Disinfection of Vines and Graft Bearers. — Sannino advises for 

 this purpose sulphocarbonate of potassium in 0*05 per cent solution ; 

 for disinfection to be complete immersion must last two hours. 

 Dufour recommends for the disinfection of graft bearers coming from a 

 phylloxera district the steeping of these in a solution of the following : 

 sulphocarbonate of potash 0*5 per cent ; soft soap 5 per cent ; pyrethra 

 powder 1 per cent ; tobacco juice 1 per cent. 



Carjyocapsa pomonella (Pyrale du Pommier) (the codlin moth) ; 

 Carj)ocapsa funebrana, Fr. (? Carcocapsa nigricane) (the red plum 

 grub). — Montillot recommends watering the soil at the foot of the trees 

 in autumn, after collecting the fruit, with a solution containing 1 per 

 cent of sulphocarbonate potassium. 



Conchylis ambignella, Hubn, (cochylis of the vine). — Dufour tried 

 to combat this insect by spraying with sulphocarbonate, but he did not 

 kill the caterpillar. A bouillie containing 1 per cent of sulphocarbon- 

 ate and 3 per cent of soap destroyed the insects but scorched the buds, 

 which browned and finally dropped off. A 0-1-0-05 per cent solution 

 does not injure the plant and kills all underground larvae. 



Formica (ants). — An excellent means of destroying an ant-hill con- 

 sists in the use of sulphocarbonate. A small trench is dug round 

 the ant-hill and it is watered in the morning as Jar as possible, when 

 the ants have not yet gone out, with an O'O per cent solution. Half 

 a litre to a litre of this solution suffices to destroy an ant-hill. After- 

 absorption of the liquid it is well to beat the earth down. 



Gale7~tica calmariensis (galeruca of the elm) ; Galeruca Alni 

 (galeruca of the alder). — Sulphocarbonates in solution applied in 

 August destroy these insects so injurious to the trees in our parks 

 and public promenades. [See p. 137.] 



36. Xanthogenate of Potassium, C^H^OCSSK. — Definition. — 

 This compound is the potassium salt of the ethylic ether of dithio- 

 carbonic acid, OHCSSH. 



Preparation. — By acting with an excess of carbon disulphide on 

 absolute alcohol saturated with caustic potash. The crystals of 

 xanthogenate of potassium formed abundantly are washed with 

 ether. 



Properties. — Xanthogenate or ethyl sulphocarbonate of potassium 

 forms colourless or slightly yellowish needles ; they are soluble in water, 

 likewise dissolving in 5-6 parts of absolute alcohol. The decom- 

 position of the aqueous solutions into carbon disulphide, ethyl alcohol, 

 and potash begins at a temperature of 25" C. (77'' F.), to be completed 

 on boiling. Xanthogenate of potassium stops lermentation like carbon 

 disulphide and coagulates albumen. Schwartz found that the action 



