16 Effect of Copper Compounds 



it to be recognised with certainty in one gram of ash, even by means of 

 the -ammonia reaction. Samples of white oak from the clay soils, and 

 plants from the dolomitic horizons also gave evidence of copper in one 

 gram of ash, though less was present than in the first case considered, 

 but with plants grown on relatively pure chalk 100 grams of ash had 

 to be examined before copper could be recognised with certainty. 



E. O. von Lippman found traces of copper in beets, beet leaves, and 

 beet products ; Passerini estimated as much as '082 / copper in the 

 stem of chickpea plants, though he regarded this figure as too high; 

 Hattensaur determined '266 / CuO in the total ash of Molinia ccerulea 

 ("006 / of total plant, air-dried). 



After this Lehmann (1895, 1896) carried out more exhaustive studies 

 on the subject of detecting and estimating the copper in various articles 

 of food : wheat, rye, barley, oats, maize, buckwheat, and also in various 

 makes of bread ; potatoes, beans, linseed, salads, apricots and pears ; 

 cocoa and chocolate. He found that only in those plants which are 

 grown on soil rich in copper does the copper reach any considerable value, 

 a value which lies far above the quantity present in an ordinary soil. 

 Plants from the former soils contained as much as 83 560 mg. Cu 

 in 1 kilog. dry substance, whereas ordinarily the plants only contained 

 from a trace to 20 mg. Apparently the species of the plants concerned 

 seems to be of less importance for their copper content than is the 

 copper content of the soil. The deposition of copper (in wheat, 

 buckwheat and paprika) is chiefly in the stems and leaves, little being 

 conveyed to the fruits and seeds, so that a high content of copper in the 

 soil does not necessarily imply the presence of much copper in the grain 

 and seed. The metal is variously distributed among the tissues, the 

 bark of the wood being the richest of the aerial parts in that substance. 

 The form in which the copper exists in the plant is uncertain and it is 

 suggested that an albuminous copper compound possibly exists. 



Vedrb'di (1893) tackled the problem at about the same time as 

 Lehmann but from a rather different standpoint. He ratifies the 

 statement as to the absorption of copper by plants, and going still 

 further he states that in some cases the percentage of copper found in 

 the seed may be four times as great as that occurring in the soil on 

 which the plants grow, quoting one instance in which the soil contained 

 051 /o CuO and the seed '26 % CuO. It is assumed that copper must 

 play some physiological r61e in the plant, but no explanation of this 

 action is yet forthcoming. Lehmann criticised Vedrodi's figures of the 

 copper content of certain plant ashes, and the latter replied in a further 



