30 



Li^tructions to Field Parties. 



The dilutions are as follows, the figures representing the per- 

 centage concentration to which the solution is to be reduced: 



Tu obta'ni Jhniiinq vahtex. 



Note. — S. and ssc, sand and sandy loam; sc, loam; sec, clay loam; c and 

 he, clay and heavy clay soil. 



The result will give the cell resistance, when filled with satu- 

 rated soil, at 60° F., corresponding to the limiting values to be 

 inserted in the following table: 



Table of UmitliKj values. 



Note. — If it is desirable to determine the 3 per cent limit in the soil, portions 

 of the composite solution will have to be concentrated by evaporation accord- 

 ing to the above directions so as to contain the ]>erceiitage of salt given in the 

 table. The cell filled Avith such concentrated solutions gives a resistance too 

 low to be read on the instrument, and it will be necessary to take a measured 

 amount of the solution in the cell, as for example, one-fourth or one-fifth its 

 capacity. Determine the resistance and divide it by 4 or 5. as the case maybe. 

 This gives the resistance of the cell when tilled. For these concentrated solu- 

 tions the readings will be rather indefinite. Keep the cell electrodes well 

 cleaned at all times. 



