108 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



Chili saltpetre forms thick beds, which extend on the surface of the 

 soil under a thin bed of clay. 



Properties.— The crystals of nitrate of soda are anhydrous, per- 

 manent in di-y air, but deliquescent in moist air. They are much more 

 soluble in hot water than in cold water ; 100 grammes of water dissolve 

 80 grammes of nitrate at 10" C. and 217 grammes at 119° C. 



Action on Plants. — Nitrate of soda is a plant food, but like most 

 salts in strong solution, it is injurious to certain plants. Steglich 

 submitted the most diverse plants to a 30 per cent solution and to one 

 of 15 per cent with the following results : — 



TABLE XVII. — Showing the Effect of a 30 per cent Solution A and of a 15 jjer 

 cent Solution B of Nitrate of Soda on Different Plants. 



The property of nitrate of soda of killing certain plants without killing 

 others has been utilized in farming to free fields invaded by certain 

 adventitious plants. Duserre recommends the use of a 20 per cent 

 solution to destroy mustard in cornfields. It is preferable not to use 

 nitrate of soda alone, but mixed with a little blue vitriol. The young 

 mustard dies after watering with a solution containing 10 per cent of 

 nitrate of soda and 2 per cent of blue vitriol. Older mustard requires 

 a solvation containing 3 per cent of blue vitriol and up to 20 per cent 

 of nitrate of soda ; 10 hectolitres (22 gallons) of this solution are 

 required per hectare (2^ acres). The use of nitrate of soda has, in 

 this case, the advantage of serving as a manure to the grain crops, 

 and by stimulating their growth renders them more apt to struggle 

 against parasites. However, Nijpels believes that nitrate of soda, as 

 the sole manure, encourages the development of the rust of cereals. 



Action on Fungi. — Nitrate of soda should, logically, act like 

 nitrate of potash on the spores of fungi. The latter salt has been 

 studied in a very complete manner by Wuthrich. 



Action on Insects. — Smith regards a 4 per cent solution of nitrate 

 of soda as a good insecticide. Concentrated solutions of nitrate of 

 soda spread on the land are injurious, according to Miss Ormerod, to 

 the larvae of the Tipula ; according to Taschenberg, to the larvie of the 

 Elaterides ; and according to Weiss, \iO Nematodes, and particularly to 

 the Tylenchns devastatrix, Kuhn (eelworms of wheat), which cause the 

 disease known as the Nicl du Froment. 



27. Arsenite of Soda, Na^AsoOs. — Preparation. — By boiling 1 

 part of arsenious acid with 2 parts of soda ash. 



Properties. — Arsenite of soda is much more soluble in water 



