Materials and Formulas. 123 



insecticide nor of the fungicide appears to be weakened, and 

 the presence of the lime in the Bordeaux mixture entirely pre- 

 vents any injury to foliage. The arsenites are mixed with 

 the fungicide in the same proportions as if clear water were 

 the diluent. Other combinations than the above are not so 

 satisfactory. 1 



When used dry, both London purple and Paris green may be 

 applied pure, provided a uniform and economical application 

 can* be made. It is, however, customary to mix the poisons 

 with flour, leached ashes, plaster, air-slaked lime, soot, and 

 similar substances, using 1 part of the insecticide to from 5 to 50 

 of the diluent, the required amount of the latter being less 

 when the two are thoroughly mixed and carefully applied. 

 But since the introduction of improved machinery, the liquid 

 applications are generally preferred. The price of Paris green 

 varies from eighteen to thirty cents per pound. 



ARSENITE OF LIME ; CA 3 (AsO 3 ) 2 (Normal). An arsenite of 

 lime is formed when arsenious acid and lime are boiled together, 

 as already described under ARSENIC. About three-fourths of 

 London purple is made up of this material, according to analyses 

 made at the Cornell experiment station. 2 The arsenite of 

 lime is insoluble in water, and is not injurious to foliage. As 

 an insecticide it is probably not surpassed by any compound of 

 arsenic; it is advisable to mix some coloring matter with the 

 poison to lessen the danger of mistaking it for some other 

 article. 



English Purple Poison. An analysis of this preparation 

 shows the total amount of arsenic trioxide to be 36.75 per cent 

 of the material. Of this amount, 14.58 per cent is soluble in 

 water. This insecticide has as yet been tested only to a limited 

 extent, but my own experience with it has been that the fol- 

 lowing proportions may be used with success against the potato 

 beetle, an insect which is destroyed with greater difficulty than 

 many other pests : 



English purple poison 1 ounce. 



Lime 1 " 



Water 4 gallons. 



1 See Cornell Agric. Exp. Sta. 1891, Dec. Bull._35, for accounts of experiments 

 in combining various fungicides and insecticides. 



2 Cornell Agric. Exp. Sla. 1890, July, Bull. 18, 36. 



