POISONOUS METALS ON SPRAYED FRUITS AND VEGETABLES. 3 



remedy against the cabbage worm, applying "just enough to make a 

 slight show of dust upon the leaves." These discoveries were quickly 

 adopted in practice, and arsenicals were generally accepted as the 

 best destroyers of external chewing insects. 



The most important insecticides recommended, other than Paris 

 green and London purple, were Scheele's green (113) in 1875, white 

 arsenic plus lime (67) in 1891, and lead arsenate (40) in 1893. Until 

 recently Paris green and lead arsenate have been the most extensively 

 used, but calcium arsenate, now on the market, promises to become 

 one of the leading arsenical insecticides. 



The use of Bordeaux mixture originated in France near the city of 

 Medoc. Viticulturists noticed that the vines near the highways, 

 which had been sprinkled with a paste of milk of lime and copper 

 sulphate to prevent thieving, did not suffer from, niildew. Prof. 

 Millardet, in 1882, attributed the beneficial action to copper, and later 

 proposed a mixture of copper sulphate, lime, and wat«r, since known as 

 Bordeaux mixture (88) (89) . The mixture was immediately accepted 

 not only in France but in the United States, where F. Lamson 

 Scribner (116) was probably the first to publish a formula for it as a 

 result of the work in France. Its use has been extended to the preven- 

 tion of so many plant diseases that to-day it is perhaps the most 

 important fungicide. 



When copper compounds were recommended as fungicides, the 

 question arose as to whether or not spraying with them would leave 

 a dangerous amount of copper on the grapes or in the wine. 



Perrett (107) stated, in 1885, that there would be no danger of 

 introducing copper into wine made from grapes sprayed with copper 

 salts, because the hydrogen sulphid formed during fermentation 

 w^ould precipitate the copper as the insoluble sulphid. Quantin (1 1 1) , 

 in 1886, concluded that the reduction of the sulphate of copper by the 

 ferments was sufficient to efi^ect the total elimination of the copper 

 in wine, but that aeration of the lees which inclosed the precipitated 

 sulphid of copper should be avoided. Chuard (23) announced in 1887 

 that the copper was present in the must as copper malate, but that it 

 was precipitated during fermentation as the sulphid and tartrate. 



In October, 1885, Millardet and Gayon (90) obtained the following 

 amounts of copper from vines that had been sprayed with Bordeaux 

 mixture in July: 



Fresh leaves (rng. per kgm.) 19. 1—95. & 



\'ine branches (mg. per kgm.) 5. 8 



Grape stalks (mg. per kgm.) 15. 0-18. 6 



Marcs (mg. per kgm.) 11. 1-21. 9 



Musts (mg. per liter) 1. 0- 2. 2 



Wines (mg. per liter), irum doubtful traces to less than 0. 3 



