H. B. Hutchinson and K. MacLrnnan 



01 



of the methods hitherto employed. PreUminary work witli sodium 

 carbonate and bicarbonate gave unsatisfactory results inasmuch as 

 deflocculation of the clay compounds of the soil occurred and adversely 

 affected the rate of filtration ; a coloured extract difficult of titration 

 was obtained and, furthermore, positive absorption was shown even in 

 the case of neutral soils containing an abundance of carbonate initially. 

 Some of these results' are given below. 



Table IV. The Absorptive Power of Soils for Sodiiiiii Carbonate. 



In view of these unsatisfactory results recourse was then had to 

 the use of a solution of calcium bicarbonate, and after minor modifica- 

 tions as to period of digestion, strength of solution, etc., this method 

 has been used with a large number of soils under well controlled con- 

 ditions. 



The Method. The required solution may be prepared eithei' bv 

 passing a current of carbon dioxide into a suspension of calcium car- 

 bonate in distilled water, or by means of a "Sparklet'' or refillable 

 soda-water syphon, for which bulbs of compressed carbon dioxide are 

 nsed. The latter method is the more convenient and perntits of the 

 preparation of a saturated solution within quite a short time. A large 

 excess of carbonate must be used (about 10 grms.) in order to provide 

 an abundance of small particles which pass readily into solution and the 

 syphon requires occasional gentle shaking for about 1.5-20 minutes. 

 The contents may then be diluted with one-third its volume of distilled 

 water and filtered; this will result in the formation of a solution of 

 approximately N/50 strength. 



For a determination of acidity, or lime requirement, 10-20 grms. 

 of the soil are placed in a bottle of 500-1000 c.c. capacity together with 



'- For general convenience and purposes of comparison the data from our soil examina- 

 tions are stated in terms of calcium carbonate required to bring the soil to the neutral 

 point. This allows of direct interpretation for general field work, each 0-1 per cent, being 

 taken as equal to 1 ton per acre of 2J million pounds of soil. In specific cases it is advisable 

 that the apparent specific gravity of the soil be determined. 



