386 Influence of Mines upon Land and Livestock 



In order to obtain some information on this subject tlie following 

 experiments were carried out: 



[a) Drainage waters from afiected soils were tested for the presence 

 of lead. Negative results were obtained with the majority of samples. 

 In a few cases only mere traces of lead were found to be present. 



(6) 10 litres of water were poured on to 10 kgm. of soil, containing 

 1-3 per cent, of lead and 11-2 per cent, of organic matter, in a tub. The 

 mixture was allowed to stand, with occasional stirring, for three months. 

 At the end of this ^jeriod the total amount of lead present in solution in 

 the water was found to be -003 gm. 



(c) The amount of lead extracted from a number of soils by means 

 of various solvents was estimated. The results are given in Table X. 



No appreciable amount of lead was extracted from any of the .samples 

 by treatment with water for seven days. A small trace was obtained in 

 the case of Sample B. This sample was found to be slightly sour and 

 probably a small cpiantity of pyrites was contained in the refuse which 

 contaminated the soil it represents (Frongoch). 



If we leave the case of peaty land out of consideration it is obvious 

 that lead is present in the affected soils in forms which are only very 

 slightly soluble in the soil water or in water saturated with carbonic 

 acid. The degree of solubility in 1 per cent, citric acid is quite appreci- 

 able, and there appears to be a tendency for the treatment with this 

 .solvent to extract about 25 per cent, of the total quantity of lead 

 present. These results, and other considerations already mentioned, 

 may seem to indicate that the lead is present as carbonate. But, in 

 practically all the samples dealt with the amount of soil carbonate 

 present is too low to correspond to the citric-soluble lead. Consequently 

 it seems highly probable that when lead sulphide is acted upon in a soil 

 deficient in lime, the ultimate resvlt is a combination of the lead with 

 some of the organic compounds of the soil. It is possible of course that 

 the formation of lead carbonate may be an intermediate step in such a 

 process. 



