abstracts: soil physics 577 



CHEMISTRY. — The possibilities and limitations of the Duclaux method 

 for the estimation of volatile acids. L. J. Gillespie and E. H. 

 Walters. Journ. Amer. Chem. Soc. 39:2027-2055. 1917. 

 Direct methods were found for the calculation of the results of 

 analyses by the Duclaux method, and a study was made of the method 

 by means of these methods of calculation. If a mixture can first be 

 shown to contain not more than three volatile acids (of the fatty series) 

 in significant quantities, then a single distillation will serve for the quan- 

 titative analysis (and to a certain extent the qualitative analysis) 

 without too great error. The errors for four acids are too great. If 

 four or more acids are present in significant quantities the mixture 

 must be fractionated before applying the calculations into mixtures 

 containing only three acids in significant quantity. The methods of 

 calculations are applicable to distillations made in other ways, for iij- 

 stance to steam distillations at constant volume. In the addendum, 

 an especially simple and rapid graphic method is given for the calcu- 

 lation for the case of three acids. This method has the advantage over 

 the lea^t square method, as any desired weight can be given readily to 

 any observation. L. J. G. 



SOIL PHYSICS. — The action of neutral salts on humus, and other ex- 

 periments on soil acidity. Louis J. Gillespie and Louis E. 

 Wise. Journ. Amer. Chem. Soc. 40: 796-813. 1918. 

 The action of humus on solutions of sodium, potassium, and barium 

 chlorides of different strengths was studied by means of the hydrogen 

 electrode. The measurements showed a large increase of hydrogen-ion 

 concentration as a result of the action. The effect was greatest in the 

 case of barium chloride. Similar effects of smaller magnitude were 

 seen in the action of potassium chloride on true solutions in the ab- 

 sence of humus or undissolved substances ; these effects made it unsafe 

 to draw conclusions as to the detailed mechanism of the process in the 

 case of humus. 



Some experiments with litmus paper served to make clear the difficul- 

 ties and limitations of the litmus-paper test as applied to soils and soil 

 extracts. These experiments make it plain that there is no ground 

 for a recent classification of soils which respond in the moist state to 

 blue litmus paper into two types: "truly acid" and otherwise, according 

 to the behavior of the litmus paper toward the aqueous soil extract. 

 Litmus paper cannot be used, without suitable precautions, to arrange 

 soils in the order of their intensities of acidity. There seems to be no 

 reason to assume a mysterious element in soil acidity. L. J. G. 



