ZINC SULPHATE. 165 



58. Zinc Chloride, ZnClo. — Preparations. — By dissolving zinc 

 clippings [or zinc scrap] in dilute hydrochloric acid. By evaporating 

 the solution the anhydrous salt, butter of zinc, is obtained. 



Properties. — Zinc chloride is a white deliquescent solid soluble iu 

 water in all proportions ; exposed to air it liquefies rapidly. 



Action on Fungi. — Zinc chloride behaves like zinc sulphate 

 (Wuthrich). All remarks made on zinc sulphate (farther on) apply to 

 zinc chloride. Tried comparatively against copper compounds on the 

 Peronospora viticola, De By., by Sbrozzi, its effect was inferior to blue 

 vitriol. By the use of a 1 per cent solution the uredospores of Puccinia 

 coronata, Corda, are checked in their development [Hitchcock and 

 Carleton]. 



59. Zinc Sulpliate, ZnSOj, IK.fl (white copperas). — Prepara= 

 tion. — By roasting crude zinc sulphide at a low temperature a mixture 

 of zinc and iron sulphates is formed which is dried and calcined to de- 

 compose the sulphate of iron. The mass is then lixiviated with hot water, 

 filtered, and the solution of zinc sulphate evaporated to crystallization. 



Properties. — Zinc sulphate forms colourless crystals with a bitter 

 styptic taste. It dissolves in 2^ times its weight of water at 15° C. and 

 ia its water of crystallization at 100° C. It is used in medicine as an 

 emetic in doses of 8-15 grains, as a collyria, gargle, and injection. 

 It is used as a disinfectant ; it acts like sulphate of iron. 



Action of Zinc Sulphate on Plants.— Sulphate of ziac shares 

 the pi'operty that the sulphates of iron, copper, and other salts have of 

 stimulating the growth and vitality of the plant if absorbed in small 

 doses and of being poisonous in large doses. 



In 1869 Eaulin described this action on Aspergillus niger. Eichards 

 then Ono examined this property of zinc sulphate on Asjyergillus niger, 

 Penicillium glaiicitm, &nd the Sblgee Protococcus and Chroococcus, Stigeo- 

 clonium and Hortnidium, and determined the stimulating action of zinc 

 salts. As soon as the dose is higher than that required for stimulation, 

 these salts retard or prevent the formation of spores. The dose re- 

 quired to stimulate algae is much less than that required to stimulate 

 fungi. Kanda made similar trials with Pisum and found that the 

 stimulating action of zinc sulphate is produced when the nutritive 

 solutions do not contain more than 0-00000015 to 0-0000030 per cent 

 of zinc sulphate. Nobbe, Biissler, and Will found that peas and maize 

 died in three days if the nutritive medium in which they grew contained 

 1 per ceat of zinc as nitrate of zinc. This poisonous action is much 

 less pronounced and sometimes does not occur in darkness (Baumann). 

 Many plants, chiefly conifers, bear without injury 1 per cent sulphate 

 of zinc without dying but afterwards show great defects in growth 

 (Baumann). Konig found in fact 2-78 per cent of zinc in the ash of 

 beech and maple stunted by slow poisoning by zinc. There even exist 

 plants which seek media rich in zinc minerals for their development ; 

 these are Viola latea {forma calaminaria) a,nd Thlaspi alpestre. Zinc 

 salts behave like blue vitriol and other poisonous salts in nutritive 

 solutions where the roots are in direct contact with the soluble salts ; 

 these are poisonous in comparatively small doses because the plants 

 readily absorb them in large quantities, but the same plants cultivated 



