18 



and 1,000 c.c. capacity respectively, connected by a glass tube and 

 each provided with tap funnels. The smaller flask contains the soil, 

 the latter is to hold the alkali for absorbing the C0 2 . The apparatus 

 is partially evacuated (a water pump suffices for this purpose), the 

 alkali is run into the larger and the acid into the smaller flask. 

 After the first action is over air is allowed to bubble slowly through 

 the mixture of soil and acid in order to carry the remaining CO a 

 into the larger flask. The C0 2 is then determined by titration. 



XVI. "The Determination of the Lime Requirements of 



Soils." H. B. Hutchinson and K. MacLennan. 

 Chemical News, 1914. 110, 61. 



A new method is proposed for the determination of the lime 

 requirements of the soil. 10 to 20 grams of the soil are placed in 

 a bottle of 500-1,000 c.c. capacity together with 200-300 c.c. of 

 approximately N/50 solution of calcium carbonate, and the air in 

 the bottle is displaced by a current of carbon dioxide in order to 

 insure against possible precipitation of calcium carbonate during the 

 period of the determination. The bottle is then placed in a shaking 

 machine for three hours, after which time the solution is filtered 

 and an aliquot portion of the filtrate is titrated against N/10 acid, 

 using methyl orange as indicator. The difference in strength of this 

 filtrate and that of the initial solution represents the amount of 

 calcium carbonate absorbed, each cubic centimetre of N/10 acid being 

 equal to 5 mgrms. calcium carbonate. The method has been found to 

 provide a useful index of the lack of base or "sourness" of the soil. 



XVII. "The Evaporation of Water from Soil." BERNARD 

 A. Keen. Journal of Agricultural Science, 1914. 6, 

 456—475. 



The evaporation of water from sand, silt, china clay, and ignited 

 soil is a relatively simple phenomenon which can readily be explained 

 by the known laws of evaporation and diffusion. The evaporation 

 from soil is more complex, something being present which operates 

 in making the relation between the soil and the soil water of a 

 different and closer nature than in the case of sand, etc. The effect 

 is not due to the soluble humus, for the removal of this material 

 from the soil does not appreciably affect the phenomena of evapora- 

 tion. Any possible effect of the insoluble organic matter is largely 

 eliminated by the consideration that ignited sand or silt behaves like 

 the unignited material. 



But when the colloidal properties of the clay are destroyed by 

 ignition, the evaporation curve is completely altered, and becomes 

 identical with that given by sand or silt. Again, evaporation from 

 china clay, which shows very feeble colloidal properties, is of the 

 same character as that from sand. We may infer then, that the 

 colloidal properties of the clay fraction are partly, if not mainly, 

 responsible for the characteristic shape of the evaporation curve 

 from soil. 



Further information on the process of evaporation has been 

 obtained by a mathematical examination of the rate curve for soil. 

 Two factors have been distinguished, which operate over practically 

 the whole range of water content dealt with in these experiments. 



