COPPER SULPHATE (BLUE VITRIOL). 205 



but in presence of an insoluble compound. The plant will absorb the 

 homcEopathic quantities which are beneficial to it, dissolving them by 

 means of the acid juices of its roots, by its chemical and physiological 

 exertions. The soil is capable of absorbing enormous quantities of blue 

 vitriol without the latter injuring the plant (the soil naturally contains 

 copper; Vedrosi found in arable land 001-0*15 per cent of copper 

 oxide, the average amount is from 0-06-0'08 per cent). Viala watered 

 vines in pots regularly for three months with a solution of blue vitriol 

 and mixed in this soil the dose of 200 grammes of this salt without 

 the vine perishing. Girard cultivated rye, oats, clover, and potatoes 

 on a soil treated with 1-i- metric tons of blue viiriol per hectare (1320 lb. 

 per acre). Taft concludes from his experiments that the soil does not 

 refuse to grow plants until it contains 1 per cent of copper. To prove 

 that copper sulphate incorporated in a soil is no longer soluble, Gorup- 

 Besanez watered 240 cubic centimetres of soil with a O'l per cent 

 solution of blue vitriol. This soil, washed at once with 500 cubic 

 centimetres of water, gave up no trace of copper to the water. 

 Similarly, Nobbe, who watered 152 grammes of dried soil with 150 

 grammes of blue vitriol was only unable to recover with 2 litres of 

 water 7*1 per cent of the blue vitriol used. In practice it has been 

 found that the watering of plants even with comparatively strong 

 solutions of blue vitriol is far from being injurious. On the contrary, 

 it is salutary. Eumm and Pichi found that vines watered with 5 per 

 cent solutions of blue vitriol, when the sap begms to circulate, resist 

 mildew and show a certain immunity to cryptogamic diseases. But 

 the amount of copper must not be too small ; 5-k gallons per stock of 

 a 1 per cent solution do not prevent mildew from attacking the vine. 

 But complete immunity is obtained with 5^ gallons of a 5 per cent 

 solution. Besides this immunizing action blue vitriol possesses a 

 stimulating power on all the vital functions of the plant, like green 

 vitriol ; plants become vigorous, their leaves more fleshy, of a deeper 

 green, and the vitality of the plant is prolonged. Hence it may be 

 concluded that the vine is capable of absorbing copper by the roots. 

 Is that possible ? 



As far back as 1819 John experimented on the absorption of copper 

 by the roots. By mixing carbonate of copper with the sterilized sand 

 used for his cultures he could not find the presence of an abnormal 

 quantity of copper in the ash of the experimental plants. But when 

 these plants were watered with very small quantities of nitrate of copper, 

 the copper absorbed by the roots was ponderable. Peas cultivated in 

 this medium contained in their ash sufficient copper to give a red pre- 

 cipitate with yellow prussiate. The ash of barley, cultivated in the 

 same condition, contained it in such large amount that it could be 

 precipitated and estimated by iron. Buchhloz and Meissner also found 

 that roots could absorb copper under a form which it has not yet been 

 possible to define. Tschirch has shown that the potato absorbs the 

 copper applied to the soil, even though the latter is watered with 4 

 kilogrammes (8"8 lb.) of blue vitriol in solution per 2 cubic metises of 

 earth. The amount of copper absorbed is the greater the larger the 

 proportion of copper applied. These results also confirm the fact that 



