8 



than with Paris green. It seems probable that a part of this is made up 

 of calcium arsenite and arsenate, which have gone into solution, but at 

 the same time, it is safe to say that Paris green is the safer insecticide. 

 The addition of lime to the water mixture of the London purple is even 

 more essential than with Paris green. 



Commercial Substitutes for Paris Green. 



The fact that the use of lime along with Paris green and London 

 purple has been so generally recommended has given the manufacturer 

 or arsenical insecticides an excuse for making and offering for sale many 

 mixtures containing widely different forms and quantities of arsenic com- 

 pounds. Many of these substances are poor substitutes for good Paris 

 green. Some of them contain very little arsenic or any other form of 

 poison, while in others there is a large amount of arsenic; but, unfor- 

 tunately, it is not always in such a state of combination as to be safe for 

 use as an insecticide. 



Among the mixtures poor in arsenic, the following have been ana- 

 lyzed in our own laboratory : — 



Black Death : One of the newer insecticides recently offered for 

 sale in this Province is "Black Death." It is sold at 2 cents per pound, 

 or 15 pounds for 25 cents. The composition of this substance, according 

 to our own analysis, is as follows : — 



Moisture 10. 42 



Sand, etc 6.37 



Carbon 17-39 



Sulphur trioxide 23.72 



Calcium oxide 23.30 



Magnesium oxide 2.16 



Carbon dioxide 7-9° 



*Paris green °-43 



Undetermined (volatile matter, water of crystallization). 8.31 



100.00 



This insecticide is composed almost entirely of charcoal, sand, and 

 gypsum. The only substance present which will poison insects is the 

 Paris green. If mixtures with so small an amount of poison will kill 

 insects, it will be cheaper to buy a pound of Paris green and mix it with 

 200 pounds of gypsum. Paris green can be bought for 20 cents per 

 pound. In Black Death it costs $3.86 per pound. 



* Copper oxide .13 per cent. ; Arsenic trioxide .12 per cent. 



