753 



tion of the radish. Conifers are very resistent. They withstood a solution 

 containing i per cent, zinc while the Angiosperms died with even 5 mg. zinc 

 per litre and, indeed, older plants died in general more quickly than did 

 young ones. 



The effect of the poison manifests itself by a striking change in color of 

 the diseased plants. Scattered small areas of a metallic lustre on a rusty 

 yellow color appear on the leaves and finally spread over the whole surface. 

 The fact that the zinc attacks the chlorophyll apparatus especially, thereby 

 hindering the work of assimilation, is proved by the observation that seed- 

 lings in which the chlorophyll grains are not yet matured as well as plants 

 grown in the dark and fungi behave indifferently to relatively highly con- 

 centrated zinc solutions. 



Zinc carbonate and zinc sulfate placed in the soil exercise an injurious 

 effect. In themselves, to be sure, they are not injurious although they are 

 soluble in pretty considerable amounts in water containing carbon dioxid, 

 whereby the zinc sulfid is first changed to zinc carbonate. But their dan- 

 gerous action lies in the transformation which the zinc undergoes in the 

 form of vitriol with the potassium, calcium, and magnesium salts. In this 

 these nutrient substances become soluble and may be wasted away. In poor 

 sandy soils sterility may, indeed, be produced and the injuriousness of irri- 

 gation with waste water from zinc smelters lies especially in this removal of 

 the nutrient substances. 



The injurious solubility of zinc in the soil depends essentially on the 

 amount of calcium carbonate contained in it. In the presence of this min- 

 eral to possibly four times the amount of the zinc sulfid no more zinc will 

 be dissolved. A soil ruined by zinc sulfate can be improved by the addition 

 of substances which render the soluble zinc salts insoluble. Humus has 

 been proved to be splendid and, on this account, fertilization with moor soil 

 can be recommended. In the absence of this, abundant stable manure, clay, 

 or marl may be used. Marl, or calcium, must be given under all conditions. 



Tschirch mentions, in regard to injuries due to lead salts, that a peculiar 

 kind of dwarfing is produced. The plants which have received i kg. mennig 

 (red oxid of lead) to 2 sqm. of surface remain small and do not bloom (lead- 

 nanism) \ Devaux- found that lead solutions in a dilution of 1-10,000,000 

 acted injuriously. This metal was fixed by the cell wall and contents. 



To purify waters containing zinc sulfate, the use of filtering layers of 

 limestone dust and moor earth could be recommended; insoluble carbonic 

 and humic zinc oxid is formed in them. 



Water Containing Iron Sulfate. 



The waste water from mines and washeries of sulfur silicate and from 

 hard coal mines, the water which drains from piles of hard coal culm and 



1 Tschirch, A., Das Kupfer voni Standpunkt der gerichtlichen Cheniie usw. 

 Stuttg-art 1893, F. Enke. 



2 Devaux, De I'absorption des poisons metalliques tres dilues par les cellules 

 vegetaux. Conipt. rend. 1901, cit Just's Jahresber. 1902, II, p. 353. 



