110 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



without drawbcack, for it burns the leaves of the vines treated. Care 

 should be taken to wash these a few hours after treatment. Muhlberg 

 found borax solutions did not kill the Schi.zoneura ianigera, Hausm., 

 against which it had been recommended. 



29. Carbonate of Soda, NaXOy. — Preparation.— By the Solvay 

 (Brunner, Mond) process principally. A concentrated solution of 

 common salt is first saturated with ammonia, then a prolonged current 

 of carbonic acid is passed through ; bicarbonate of ammonia is pro- 

 duced, which acts on the common salt to convert it into carbonate of 

 soda. The precipitate is filtered, drained, and calcined. 



Properties. — Carbonate of soda crystallizes in prisms ; the crystals 

 lose their water of crystallization at the ordinary temperature. Heated, 

 they melt in their water of crystallization, dry, and form calcined 

 carbonate of soda (soda ash), which is an amorphous white powder 

 containing no water. Soda crystals are much more soluble in hot 

 water than in cold : the maximum solubility is at 38° C. ; one gallon of 

 water dissolves 6-04 lb. at 14° C, 166-6 lb. at 38' C, and 44-5 lb. at 

 104" C. Carbonate of soda in solution has a strong alkaline reaction. 



Action of Carbonate of Soda on Plants. — Around alkali works 

 the presence of this salt, carried by the wind, does much damage. 

 Eventually the carbonate of soda, covering the leaves with a white 

 layer, more or less thick, causes them to drop off, and kills the trees 

 themselves. Eye suffers much from contact therewith ; the ears are 

 almost empty, and ihe few grains which they contain are shrivelled 

 and blackish. When plants have been in contact with carbonate of 

 soda the analysis of the ash reveals a quantity of soda superior to the 

 normal quantity. The straw of cereals is more brittle, and contains 

 less silica. Carbonate of soda acts like carbonate of potash ; when it 

 is a case of neutralizing the acidity of certain marshy lands carbonate 

 of soda may play the part of lime, and the nitric ferments, which 

 cannot act except in slight alkahne media, may thereby modify the- 

 flora of the field. In such conditions carbonate of soda, in small dose, 

 may exert a favourable influence on vegetation. 



Action on Fungi. — "Wuthrich treated the spores of different fungi 

 with sodium carbonate with the following results : A solution of 0-053 

 per cent prevents the conidia of the Phyto2)hthora injestans, De By., from 

 producing zoospores, but it does not injure their direct germination ; 

 life is only arrested by immersing the conidia in a 0-53 per cent 

 solution As to the conidia of the Peronospora riticola, De By., 

 Wuthrich found sodium carbonate more energetic ; a 0-053 per cent 

 solution hindered the growth of the spores, and a solution of 0-53 per 

 cent stopped it entirely. The uredospores of Puccmia grmninis, Pers., 

 show, more than any other spores, a great resistance to carbonate of 

 soda solutions, but germination is hindered by 0*53 per cent solution 

 and stopped entirely by immersion in a 2-65 per cent solution. 



Action on Insects. — All soft-skinned insects are sensitive to 

 strongly alkaline substances, but these substances in themselves are 

 not very powerful insecticides ; they are, therefore, combined with toxic 

 substances. 



Use. — Carbonate of soda enters into the composition of certain 



