J. C. Sanderson — Certain Minnesota Soils. 391 



Art. XXI Y. — The Radio-active Content of Certain Minne- 

 sota Soils ; by James C. Sanderson. 



Introduction. 



In a previous article,* the writer described methods by 

 which the freely emanating radium and thorium contents of a 

 characteristic New Haven soil were measured, and showed 

 how the thorium content of a soil could be estimated from a 

 sample of about fifty pounds. The results obtained for the 

 disintegrated red sandstone, near the Sloane Physical Labora- 

 tory, were 8'9 x 10 -14 gram of radium and 1*35 x 10~ 6 gram of 

 thorium per cubic centimeter of the soil. In an article entitled 

 " A Study of the Radium Emanation of the Air Contained in 

 Various Soils,"f Satterly discusses three methods of measur- 

 ing the radium content of soils ; the first two are comparison 

 methods, but the third, which he calls " the bottle experiment," 

 gives quantitative results, and he finds for a sandy soil in 

 Cambridge, England, 22 x 10 - ' 4 gram of radium per cubic 

 centimeter of moist soil and 18 x 10 -14 for the same soil when 

 dry. His figures show that about twenty per cent of the vol- 

 ume of the moist soil was water, so that, in a given volume, 

 the radio-active material actually present was very much less 

 than in the case of the dry soil. Since the apparent radio- 

 activity, or amount of free emanation, was higher in the moist 

 soil, we must conclude that the amount of moisture in a soil is 

 a large factor in its emanating power. On the other hand, 

 soil chemists consider the hygroscopic properties of a soil to be 

 a valuable index of its fertility. 



Although it has been known for some time that the radi- 

 ations from radium and its products have a stunting and 

 deforming effect upon vegetable organisms, just as they have 

 a destructive effect on animal tissue, only recently has it been 

 demonstrated conclusively that radio-active enrichment of the 

 soil, with extremely minute quantities of radium, acts very 

 beneficially upon vegetation and results in a marked increase 

 of fertility. J. Stoklasa and Y. Zdobricky^: describe experi- 

 ments in which various plants are treated with waters contain- 

 ing radium emanation. Lentils, peas and wheat, treated with 

 radio-active water, showed respective gains of 62, 116 and 164 

 per cent over the control plants. When buckwheat was sup- 

 plied with 30 Mache units every five days, it showed an 

 increase of 43 per cent over the control culture, but with 60 



*This Journal, vol. xxxii, p. 169, 1911. 

 fProc. Cambr. Phil. Soc, vol. xvi, part 4. 

 \ Comptes Kendus, vol. clvii, pp. 1082-4. 



Am. Jour. Sci.— Fourth Series, Vol. XXXIX, No. 232— April, 1915. 

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