432 NATURAL SCIENCE. June. 



Twelve pennies were left four days in twelve litres of water, which 

 then had a slightly metallic taste, and the Spirogyra plant died in it 

 in one minute. The water generally used in experiment had been 

 only one-fifth or one-tenth so strongly oligodynamic. Indeed, one 

 part of copper in one thousand million parts of water may be fatal 

 to Spirogvfa cells. The copper went into solution as cupric hydrate 

 combined with carbonic acid. Other metals, silver, zinc, iron, lead, 

 mercury, acted similarly. The salts of these metals could also render 

 water oligodynamic, and the vessels that had contained the solutions 

 retained oligodynamic power, though to a less marked extent. 



According to physicists, the saturation of a solution depends on 

 the quantity of substance that a definite quantity of water will take 

 up ; as the solution becomes supersaturated, equilibrium is restored 

 by the redeposition of the substance. The molecules of a barely 

 soluble body tend to attach themselves to some other substance, and 

 so pass out of solution. Thus copper, in water which contains 

 carbonic or other acid, gives off its molecules slowly but continuously. 

 These spread through the water, some attaching themselves to the 

 wall of the vessel. As complete saturation is reached, still more 

 molecules adhere to the walls. Should the copper be removed before 

 this stage is reached, the water withdraws some of the molecules 

 from the wall and an equilibrium is established between the copper 

 layer and the solution. If such a solution be poured into a clean 

 glass, a layer of copper molecules is again deposited, and the greater 

 area of wall offered, the more molecules will be attracted from the 

 solution. 



In this lies the explanation of the neutralising effect of the 

 various bodies above-mentioned. They simply attracted the metallic 

 molecules. When oligodynamic water was well shaken up with 

 powdered sulphur, and filtered, it was rendered completely neutral, 

 and thus also sugar or salt failed, as they themselves pass readily 

 into solution. 



As to the action of gum, albumen, etc., Nageli explains it on 

 his own " micellar " theory of the structure of organised bodies, of 

 the trutli cf which he finds here additional evidence. He considers 

 that organised bodies are built up of micellae, invisible crystalline 

 bodies, formed by the aggregation of chemical molecules, and that 

 colloid substances form with water " micellar solutions " ; the copper 

 molecules attached themselves to the micellae as they would to larger 

 bodies. The Algae themselves acted as neutralising agents when 

 their number was in excess, and in this case the molecules could only 

 act very slowly or not at all. 



Metallic substances would, in the same way, be removed from 

 lakes, rivers, etc., by the presence of large quantities of insoluble 

 substances. 



The water used in the experiment was supplied by the town 

 (Munich). It was conducted through lead pfpes terminating in the 



