CALCIUM OXIDE (QUICKLIME). 139 



poisonous ; it must, therefore, be used with great caution, especially on 

 meadows used as pasture for domestic animals. 



Weevils. — Still recommends Bad, to kill them. 



Peritelus griseus (vine weevil). — Stromer remarks its presence on 

 the hop, and recommends spraying with BaCl, solutions to kill it. 



Phorodon liumili, Schrank (hop aphis green-fly). — Metzger kills this 

 louse by spraying with 1 per cent solutions of BaCl.^. The results ob- 

 tained have been very satisfactory, and he regards this salt as more 

 efficacious than Dafour's insecticide, and extracts of quassia. As 

 aqueous solutions of Bad., want adhesiveness, Metzger recommends- 

 a paste of 2 per cent of barium chloride and 1"5 per cent of soft soap. 

 Eight days after treatment the aphides had entirely disappeared. 



Bodents. — Barium chloride acts on rodents like carbonate of 

 baryta. To exterminate them radically Hilner places bread dipped 

 in barium chloride in their runs. 



40. Barium Sulphate, BaS04. — Passerini found that pastes made 

 with barium sulpliate had no action on Peronospora riticola, De By. 



41. Barium Carbonate, BaCO^. — Preparation. — By precipitat- 

 ing solutions of barium chloride by carbonate of soda. The natural 

 carbonate (Witherite) is not used as such. 



Properties. — Poisonous, insoluble in water. 



Use. — Largely as poison for the rodents which ravage cultivated 

 land. One pound of bread is mixed with | oz. of sugar and ^ lb. of 

 precipitated carbonate of baryta ; the mass is kneaded and then divided 

 into about 2000 pills (Eessler). One lb. of barley meal is kneaded 

 with ^ lb. carbonate of baryta and the amount of water necessary to- 

 make a stiff paste and divided into pills and laid in their runs 

 (Crampe). 



42. Barium Sulphocarbonate, BaCSg. — Preparation. — By 

 treating a concentrated solution of barium monosulphide by carbon 

 disulphide, solid barium sulphocarbonate is deposited. 



Properties. — Barium sulphocarbonate is a yellow salt slightly 

 soluble in water and resists the action of the carbonic acid of the air 

 for some time ; it is more stable than alkaline sulphocarbonates, but it 

 is equally poisonous to plants, and has equal powers as an insecticide. 



Use. — Phylloxera vastatri.r, Planch, (phylloxera of the vine). — 

 Mouillefert examined its effect compared with alkaline sulphocarbonates. 

 Two vines were stripped down to the large roots and treated with 75 

 grammes (2|- oz.) of barium sulphocarbonate ; the first was not watered 

 in any way, whilst the second was immediately watered with 6-5 litres- 

 of water, say 1^ gallons. With the latter the result was perfect, whilst 

 on the roots of the first a large number of undestroyed parasites were 

 found. Barium sulphocarbonate exists a long time in the soil without 

 decomposition, and if not dissolved by heavy rain its action is too- 

 slow, and is not transmitted to the deep roots. The latter are not 

 therefore surrounded by a sufficiently poisonous atmosphere to kill the 

 phylloxera and the results are bad. 



43. Calcium Oxide (Quicklime), CaO. — Occurrence. — Widely 

 in nature ; chiefly as carbonate, sulphate, silicate, and phosphate of 

 lime. 



