86 METHODS OF DETERMINING ALKALI 



first of which 50 grams of soil are added to 500 cc. of water 

 and in one case agitated for 5 minutes, and in the other 

 case shaken intermittently for 24 hours, while in the 

 second method 50 grams of soil are added to 1000 parts 

 of water and after shaking for 8 hours allowed to stand over 

 night. 



From comparisons of methods at the Utah Station, the 

 proportion of soil to water influenced the quantity of 

 carbonate found, but had little or no influence on chlorides 

 or sulphates. 



After the solution has been in contact with the soil 

 for the desired length of time, it is poured into a Pasteur- 

 Chamberland filter and filtered under an air pressure of 

 30 to 40 pounds per square inch. The first 50 to 200 cc. 

 of the filtered solution are discarded, after which the desired 

 quantity is collected and bottled until needed for making 

 the tests of the different constituents. 



Determining Total Solids. - - The ordinary method of 

 determining the total soluble salts in the extracted solu- 

 tions is to evaporate 20 to 50 cc. of the solution to dryness 

 in a weighed evaporating dish over a sand or steam bath. 

 Some chemists gently ignite the residue further to purify 

 the salts of undesirable material, while some re-dissolve 

 the residue to get the soluble alkali salts and help eliminate 

 calcium and magnesium salts. The Bureau of Soils does 

 not determine the total salts by evaporation and declares 

 it to be unreliable. 



In Table XI is shown the total salts and the various 

 constituents of alkali as determined by the different 

 methods on alkali soils in Arizona (12). 



Carbonate and Bicarbonate Determination. - - The 

 method for determining the carbonate and bicarbonate 

 used by the Bureau of Soils (9) is described as follows: 



