508 



SCIENCE 



[N. S. Vol. XLII. No. 1084 



tent is reduced to or slightly below the 

 wilting coefficient. In the case of quartz sand, 

 for instance, the freezing point can he meas- 

 ured when the amount of water present is only 

 about 0.8 per cent. Below the wilting coeffi- 

 cient the solidification is started with some 

 difficulty, and the duplicate determinations do 

 not agree very closely, especially if the con- 

 centration of the solution is very high. Above 

 the wilting point the solidification does not 

 only start with great ease, but the determina- 

 tions can be duplicated with a surprising close- 

 ness; the values either agree exactly with one 

 another or show deviations of only a few 

 thousandths of a degree, using the Beekmann 

 thermometer. 



In determining the freezing point of differ- 

 ent classes of soil the remarkable fact was dis- 

 covered that the freezing point lowering, and 

 consequently the concentration of the soil solu- 

 tion varies directly with the amount of water 

 present. The following figures show the freez- 

 ing point lowering, using distilled water as a 

 basis of comparison, of natural soils contain- 

 ing high and rather low moisture content. 



TABLE I 



Freeeing Point Lowering of Different Classes of 

 Soil at Different Moisture Content 



Freezing-point Per Cent. 



Soil Lowering Moisture 



Sand 0.033° C. 6.22 



Loam 0.050 33.46 



Clay 0.098 24.68 



Clay 0.090 38.00 



Peat 0.021 181.60 



Sand 0.171 2.80 



Loam 0.251 25.15 



Clay 0.695 18.23 



Clay 2.290 12.00 



Peat 0.050 138.97 



It will be evident from the above table that 

 when the soils contain a hig'h moisture con- 

 tent the lowering of the freezing point, and 

 consequently the concentration, is rather small, 

 and does not vary greatly between the different 

 soils. But when the moisture content of these 

 same soils is reduced considerably, the lower- 

 ing of the freezing point is increased in some 

 cases very greatly. When it is considered that 



about 4,000 parts of mineral salts in 1,000,000 

 of water cause a depression of the freezing 

 point of only about 0.090° C, the above figures 

 for the soils with low moisture content repre- 

 sent an enormous concentration, especially in 

 some eases. 



In order to ascertain (1) the sensitiveness of 

 the method to detect differences in concentra- 

 tion in the soil solution, and (2) to see whether 

 the concentration of the soil solution can be 

 increased by the addition of mineral salts, a 

 complete nutrient stock solution was prepared 

 from which solutions were made up varying in 

 concentration from 80 to 4,000 parts per 

 million. The freezing point of these solutions 

 alone, and in contact with soils was deter- 

 mined. Some of the results thus obtained are 

 shovra. in Table II. 



TABLE n 



Lowering of the Freezing Point of Soils with a 



Nutrient Solution of Different Concentration 



Lowering of the Freezing Point 



Solution. 



Sand 



Loam 



Clay 



Peat 



P. P. M. 



0.005 



0.005 

 0.005 

 0.006 

 0.005 



0.043 



0.040 

 0.036 

 0.037 

 0.021 



0.083 



0.085 

 0.067 

 0.065 

 0.050 



The values for the soils represent the depres- 

 sion of the freezing point caused only by the 

 addition of the respective solutions; the de- 

 pression due to the soils themselves has been 

 deducted. 



An examination of the above results reveals 

 the interesting fact that the lowering of the 

 freezing point of the solutions in contact with 

 the soils does not vary very much from that of 

 the solution alone. 



There is at present no other method capable 

 of measuring the concentration of the soil solu- 

 tion in the soil or around the soil particles. 

 The foregoing method has yielded, thus far, 

 some very remarkable results, and promises to 

 give us a better understanding of the funda- 

 mental principles governing the soil solution. 

 George Bouyouoos, 

 M. M. McCooL 



Michigan Ageicultukal College 



