78 CHEMICAL PROPERTIES OF SOIL 



hour should be determined, and tabulated for com- 

 parison with the following soils : — 



{a) Sand. {c) Clay soil. 



{b) Loam. {d) Peaty soil. 



The same conditions of experiment must, of course, 

 be chosen in each case. 



Surface Tension and Capillarity. 



The movements of soil water are largely governed by the surface 

 tension displayed by the liquid when in contact with the soil 

 particles. The continuous pore-spaces of the soil, acting in the 

 same manner as capillary tubes, allow the upward and lateral 

 movement of water through the soil, and the quantity of water 

 which may be lifted in this way from the subsoil, e.g. during 

 periods of drought, is very considerable and of great importance. 

 The surface tension of water is high, but is readily affected by the 

 presence of small quantities of material in solution ; the effect of 

 adding fertilisers and manures to the soil consequently alters the 

 "lifting capacity" for subsoil water. Most of the salts present in 

 the artificial manures increase the surface tension of water, whereas 

 organic materials, dung extract, etc., have a contrary effect. 



58. Measurement of Capillarity. 



A piece of capillary tubing about 4 inches in length 

 is fixed in an upright position in a small glass vessel or 

 tube, which can be filled exactly to the same height by 

 various liquids. 



The height to which the liquid under examination 

 rises in the capillary tube is measured by a cathe- 

 tometer. The capillarity of the following liquids should 

 be measured : — 



(i) Distilled water. 



(2) Alcohol. 



(3) Dung liquor. 



(4) Sulphate of ammonia solutions, i, 5, 10, and 



20 per cent. 



