INSECTICIDES, FUNGICIDES AND DISINFECTANTS 215 



Green arsenoid is an insecticide similar to Paris green, and 

 applied in the same manner, but is less used. 



London purple is a by-product of the manufacture of 

 anilin dyes. It is composed of calcium arsenate and cal- 

 cium arsenite together with an organic dye residue. Lon- 

 don purple is quite variable in composition, and is very 

 little used. 



162. Insecticides for Sucking Insects. Kerosene emulsion 

 is prepared by emulsifying soap. A good quality of laundry 

 soap is satisfactory. Two to four pounds of soap and 5 to 10 

 gallons of kerosene to 50 to 100 gallons of spray solution are 

 the usual proportions. The soap should be dissolved in 

 from 5 to 10 gallons of hot water, placed, together with the 

 kerosene, in the spray barrel, then emulsified by pumping 

 air through the spray rod into the spray solution. Kero- 

 sene-emulsion should be used promptly after preparation. 



Soaps are sometimes used to destroy soft-bodied insects. 

 Fish-oil soap is one of the best and most commonly used 

 soaps for this purpose. Potash soap is better than soda, 

 soap. , The soap is more easily dissolved in hot water, and 

 the solution applied by means of the spray pump. A 

 solution of 2 pounds of rosin fish-oil soap in 50 gallons of 

 water is often used as a " sticker " for fungicides with poor 

 adhesive qualities. 



Lime-sulphur mixtures are prepared by boiling sulphur 

 with milk of lime. The chief constituents of these mixtures 

 are poly sulphides of calcium, the tetra- and the penta- 

 sulphide being most desired, and calcium thiosulphate. 



Nicotine solutions are obtained from decoctions of tobacco, 

 the nicotine being the active agent. One-half pound of 

 tobacco is steeped in boiling water and then diluted to 

 5 or 10 gallons. These solutions are used chiefly for the 

 control of plant lice. 



Nicotine sulphate solutions, such as Black Leaf 40 are 

 used extensively and have replaced kerosene emulsion for 

 aphis. 



