CHAPTER XII. 



RED LEAD— LEAD ARSENIATE— LEAD AESENITE— LEAD CARBONATE 

 (WHITE LEAD) — LEAD ACETATE (SUGAR OF LEAD) — SILVER 

 NITR\TE (LUNAR CAUSTIC)— SILVER CHLORIDE. 



79. Red Lead, Pb.jO^. — Preparation. — By heating massicot PbO 

 in special furnaces to -ioO^-SOO" C. 



Properties. — Red lead is a brilliant red powder, insoluble in 

 water. 



Use. — Seed beds may be completely preserved against the attacks 

 of sparrows and other granivorous birds as follows : 20 lb. of seed are 

 mixed with 1 lb. of red lead and stirred, so that the seeds may be uni- 

 formly red. The seed is sown as usual and the birds shun the land 

 where they have been sown. Von Tubeuf recommends red lead 

 particularly to preserve pine and spruce fir seeds. 



80. Arseniate of Lead, PbyAs^Oj,. — Preparation. — By acting on 

 a solution of 10 lb. of arseniate of soda with 18 lb. of lead acetate, or 

 15 lb. of lead nitrate, dissolved in water. To prepare the bouillie the 

 liquor is made up with water to 250-376 gallons. Marlatt's bouillie 

 contains 10-24 lb. of arseniate of lead and 50 lb. of glycose in 1000 

 gallons of water. 



Properties. — Lead arseniate is one of the most insoluble of 

 arseniates in water. It forms in the bouillie a finely divided precipitate 

 which remains well in suspension, which is not the case with many of 

 the arsenite greens of a density of 3 gind the consistency of which is 

 very granular. 



Action on Plants. — Owing to its insolubihty it is perfectly harm- 

 less to the plant, and that is one of the great advantages of this product, 

 for all arseniates are more or less soluble in water, and thus more or 

 less injurious to plants. Woods' experiments on potatoes have shown 

 the harmlessness of three sprayings annually and spreading 5-5 lb. 

 of arseniate of lead altogether ( ? per hectare, say 4-4 lb. per acre). 

 Besides, it was impossible to find even traces of arsenic in the tubers. 

 A bouillie containing O'5-IO per cent of arseniate of lead never 

 scorches the leaves, so that bouillies containing a large proportion of 

 poison may be used, when the insects stand strong doses of arsenic 

 and resist all arsenite of copper bouillies. 



Action on Insects. — Its poisonous action on insects is not in equal 

 doses as rapid as that of copper arsenite. Arseniate of lead is a 

 violent poison for man. Used without precaution it is as dangerous as 

 lead salts and arsenites. It chiefly affects the sight. Some cases 

 have been quoted in America where this bouillie is in constant use. 



Use. — Lead-arseniate bouillies cannot replace copper-arsenite and 

 (195) 



