SILVER NITRATE (LUNAR CArSTIC). 197 



8i. Lead Arsenite, PbAs._,0,.,. — Preparation. — Sodium arsenite 

 6 oz., lead acetate 32 oz. ; dissolve sei^arately in water, mix with solu- 

 tions, and make up the bulk to 62i gallons. It may be bought under 

 the name of arseiwid rouge (red arsenoid). 



Properties. — Precipitated arsenite of lead is finer than arseniate of 

 lead, but it is a little more soluble in water than the latter. Lead 

 arseniate is therefore preferred against plant diseases. 



82. Lead Carbonate. — Passerini tried lead carbonate against Per- 

 onospora viticola, De By., but he obtained no useful result. 



83. Lead Acetate, Pb(C,H30.,)2, 3H0O.— Preparation.— By 

 dissolving lead in acetic acid. 



Properties. — Soluble in water, with a saccharine taste. Very 

 poisonous, like all lead salts, and absorbed in small regular doses it 

 causes the complaint known as painter's coHc. 



Action of Lead Salts on Plants. — Lead acetate acts on 

 plants as on our organism. Placed in strong doses in contact with 

 . the roots of plants it kills them, yet young plants of peas, maize, 

 and oats, cultivated in nutritive solutions, are not killed in four days 

 after receiving 1 per cent of lead as lead nitrate (Nobbe, Bassler, Will). 

 By slow absorption in small doses it eventually produces a paralysis 

 of growth, an arrest of the normal growth, and a special naiiisme (?). 



Action of Lead Acetate on Parasitic Fungi. — Hitchcock and 

 Carleton found that the germinative power of the uredospores of 

 PuGcinia coronata, Corda, was reduced by immersion in a 1 per cent 

 solution of lead acetate. 



Use. — Tilletia caries, Tul. (bunt). — A commercial product with an 

 acetate of lead basis, sold as " Germinateur guarante," was recom- 

 mended for the disinfection of seed-corn. Schribaux, the director 

 of seed control of the Agronomical Institute of Paris, examined this 

 product comparatively with blue vitriol, and found it 100 times less 

 active than the latter on the spores of Tilletia caries, Tul. Lead 

 acetate cannot therefore replace blue vitriol in the disinfection of seed- 

 corn. 



PeronosjMra viticola, De By. (mildew of the vine). — Kaserer made 

 a series of experiments against this disease, spraying with the follow- 

 ing bouillies : — 



Mixture of 100 grammes of lead acetate and milk of lime. 

 250 

 500 

 ,, -500 ,, of lead nitrate ,, 



The lead hydrate which is formed by lead acetate or nitrate with milk 

 of lime appears to have, owing to its solubility in pure water, a rather 

 decided action on the spores of Peronospora viticola. Owing to the 

 rapid conversion of lead hydrate into insoluble carbonate of lead, the 

 action of the bouillie is not so lasting as that of copper bouillies. 

 Besides the adherence of the deposit is less than that of bouillie 

 bordelaise. The vines treated showed no signs of poisoning. 



84. Nitrate of Silver. — Preparation. — By treating pure silver 

 with nitiic acid the liquor forms colourless lamellae of silver nitrate on 

 cooling. 



