Action of the Atmosphere vpon nexdij -deepened Soil. 439 



tains one-fifth of its volume of oxycren. According to Guibourt, 

 when a piece of iron is immersed in such water the whole be- 

 comes electrically excited. The water, rendered more negative 

 by contact with the iron, repels its dissolved oxygen, while the 

 iron, become more positive by the contact of water, exercises an 

 unusual affinity for the oxygen. Supposing the surface of the 

 metal everywhere uniform, a film of oxide is soon produced over 

 it, and, this once effected, decomposition proceeds with increased 

 rapidity ; for as every metal is positive with regard to its own 

 oxides, it follows that the film of rust and the iron beneath now 

 form a voltaic couple of greater energy than the last'; and 

 Avhereas the electric energies were before only sufficient to bring 

 the dissolved oxygen of the water into combination with the iron, 

 they now become sufficient to decompose the water itself, and 

 hydrogen commences to be evolved. ((Quoted by Mallet from the 

 Jonrn. de Pharvt., 1818.) 



According to Thomas Thompson, the air in the water of the 

 river Clyde amounts to 3"113 per cent., and consists of 70*9 of 

 nitrogen and 29*1 of oxygen. 



Newly-boiled water has the property of absorbing a portion 

 of all gases brought into contact with it, the absorption being 

 promoted by shaking. The following table shows the quantities 

 of different gases taken up by water that has been deprived of all 

 its air by ebullition : — 



100 cubic inches of water at 60° and 30' Bar. absorb of 



Dalton and Henry. Saussure. 



Cubic Inches. Cubic Inches. 



Carbonic acid 100- .. .. 106- 



Oxygen 3"7 .. .. 6"5 



Nitrogen 1'50 .. .. 4"1 



H3-drogen 1-5G .. .. 4"G 



Sulpliuretted hydrogen .. lOO* .. .. 253- 



Oleliant <;as 12-5 .. .. lo-3 



Carbonic oxide TSG .. .. G-2 



T. Thompson. 



Ammonia 7800U" 



The estimate of Saussure is thought to be generally too high. 

 'J'\\e folhnving table shows the solubility of certain substances in 

 water: — 



100 of Water at 60» 

 dissolve 



Alumina 0-000 



Ammonia, nitrate 200-000 



snl].liatc uO'OOO 



Potash; suliihatc 'J-GUO 



„ nitrate 27-000 



„ carbonate 121-0()0 



„ bicarbonate 2.J-U00 



Sodium 



