of sodium chloride but was decreased when high concentrations 

 of the sodixim salt were used. He explained these phenomena 

 by considering that a double salt of sodium chloride and 

 mercuric chloride was formed, such as Na2HgCl4 or some sim- 

 ilar combination. He supposed that the dissociation tension 

 of this double salt was probably much lower than that of 

 mercuric chloride, a consideration which might account for 

 the decreased toxicity of the combinations in which high 

 concentrations of sodium chloride were employed. In this 

 connection, he suggests that the HgGl4 ion present when such 

 a salt as Na2HgCl4 dissociated at lower concentrations might 

 be considerably more toxic than the Hg ion, the latter being 

 probably the toxic ion of mercuric chloride. 



In a later investigation on the toxicity of copper 

 in combination with various chemical compounds, the same 



n 



writer' has shown for the spore germination of QedonftphalTiTn 



7 Clark, J. F., On the toxic properties of some copper com- 

 pounds with special reference to Bordeaux mixture. Bot. Gaz. 

 33:26-48, 1902. 



albidum and Rhizopus nigracans that ammonium nitrate, sodium 

 sulphate, potassium sulphate, and potassium chloride all 

 markedly decreased the toxic effect of both copper chloride 

 and copper sulphate. He used relatively high concentrations 

 in some cases 5 per cent of the alkali and ammonia salts r- 

 He considers the decreased toxicity just mentioned as due, 

 probably, to the formation of double salts as in the case 

 of mercuBic chloride. 



