304 Soda-Salts in Agricultw-e. 



The salt-solution, as already stated, originally contained, in 

 four deci-gallons, 41*52 grains of pure chloride of sodium. The 

 liquid, which had been left for four days in contact with the soil, 

 contained, after filtration, in four deci-gallons : — 



Grains. 



Soluble silica '36 



Oxides of iron and alumina -IS 



Chloride of sodium 36-24 



Chloride of potassium 1"04 



Chloride of map;nesium '30 



Chloride of calcium G'04: 



Sulphate of lime 7"55 



Phosphoric acid traces 



51-G9 



The chlorine contained in the solution used in the experiment 

 amounts to 25*16, and the chlorine found in the filtered soil- 

 solution amounts to 20*57, and is distributed amongst the various 

 constituents as follows : — 



Grains. 



Chlorine united with sodium 21"99 



Chlorine imited with magnesium '23 



Chlorine united with potassium *49 



Chlorine united with calcium 3-8G 



Total chlorine found 26*57 



Consequently no absorption of chlorine whatever took place ; the 

 filtered liquid contained 1*41 of chlorine in excess over the 

 quantity contained in the salt-solution before filtration, which 

 slight excess no doubt is due to the small quantities of chlorides 

 which occurred in the soil. 



It Avill be seen that whilst the whole amount of chlorine passed 

 through the soil in combination with magnesium, potassium, and 

 calcium, some soda was retained by it. The amount of soda 

 fixed by the soil is but small, for 



Chloride of s^ 



boQium. 



Before the experiment the salt solution contained .. 41*52 = 22*00 

 After contact with soil 36*24 = 19*20 



Difference 5*28 = 2*80 



Thus 3500 grains of this calcareous soil absorbed only 2*8 grains 

 of soda contained in 5*28 grains of chloride of sodium, or 1000 

 grains absorbed onlv 0*8 of a grain of soda. 



If we compare this result with the action of arable soils upon 

 potash-salts, we find that the soil has far less attraction for soda 

 than for potash. For instance, this same calcareous soil, of 

 which 1000 grains in the preceding experiment absorbed only 

 0*8 of a grain of soda, in a similar filtration experiment made 



