206 EXPEEIMEXT STATION KECORD. 



of lime soils were the results comparable. Evidently it is advisable to deter- 

 mine tlie calcium content of each soil before making a humus determination 

 by this method. The interference of carbonate may be obviated by evaporating 

 the soil with an aqueous solution of sulphurous acid. The advantages of the 

 Dennstedt method are said to lie in the fact that the results are more ac\:urate 

 and one can determine at the same time the loss in weight of a soil by inciner- 

 ation. 



Physically bound water of the soil was determined by four methods, viz, in 

 the toluol drying oven at 105° C. (for 3. 6, 9, and 12 hours), in a vacuum desic- 

 cator over phosphorus pentoxid according to Mitscherlich, at 105° C. in the air 

 bath to constant weight, and by the Schwalbe distillation method." It is con- 

 cluded that for scindy soils drying in the air bath to constant weight between 

 105 and 100° C. will yield s;itisfactory results. In loam clay and moor soils 

 the method of Mitscherlich or the distillation method of Schwalbe will .serve 

 best. As the latter method is exact enough for ordinary purposes, in view of 

 the simplicity and speed with whieh it may be conducted, it is given preference 

 over the Mitscherlich procedure. 



For determining the si^ecific gravity the von Wr'X^hem * modiflcation of the 

 Erdmenger and Mann method was found preferable to the pycnometer with 

 water, and the pycnometer with oil of turpentine. In this method 20 gm. of 

 the powdered substance in an absolutely air dry condition is placed in a 50 cc 

 flask containing 25 cc. of pure oil of turpentine run in from a 50 cc. burette. 

 The mixture is then rotated several times to remove air from the soil pores 

 and the flask is filled to the 50 cc. mark. The number of cubic centimeters 

 of turpentine remaining in the burette divided by the weight of the soil em- 

 ployed equals the specific gravity of the soU. 



A new test for soil acidity, E. TBroo ( Wi-wonsin Sta. Bui. 2-/.9 (1915), pp. 16, 

 pi. 1. figs. 4). — ^A popular description of the test previously noted (E. S. R., 32, 

 p. 610) with simple directions for making it. In order that the test may be 

 carried out on the farm or field a compact form of apparatus has been devised 

 which is illustrated. " The apparatus with accessories fits snugly into a small 

 carrying case 5* by Tj by 9 in." 



The availability of nitrogen in kelp, J. A. Cttxe::^ {Jour. Indus, and Engin. 

 Chem., 6 (191^), Xo. 7, pp. oSl, 5S2). — In view of the widespread interest in kelp 

 as a source of American potash some information as to the value and nature of 

 the nitrogenous substances present in this plant is reported. The methods used 

 were the official alkaline permanganate method (E. S. R.. 23, p. 9) and some 

 modifications of it. The neutral permanganate method noted by Street 

 (E. S. R., 23, p. 706) could not be used on account of a bulky residue and the 

 resistance to filtration. 



The official alkaline permanganate method, in its present form, was not suited 

 lor kelp, but by using increased amounts of potassium permanganate a higher 

 availability was obtained. If an adequate amount of potassium permanganate is 

 used to oxidize all the organic matter present, all, or nearly all, of the nitrogen 

 is found available. 



The chemical examination of water, sewage, foods, and other substances, 

 J. E. PcEvis and T. R. Hodgson (Cambridge, Mass.: Harvard University Press, 

 1914, pp. 228). — This is intended as a text-book for the use of students of public 

 health, health officers, and food chemists. Chemical analysis of water, sewage. 



•^Ztschr. Agnew. Chem., 21 (1908 i, Nos. 9, pp. 400-402, fig. 1; 45, pp. 2311, 2312. 

 » llitt. K. Materialprtifungsamt Gross-Li chterfelde West, 22 (1904), N'o. 5, pp. 217-220, 

 figs. 3. 



