610 EXPERIMENT STATION RECuRD. 



about 30°, allowing the tip of the crucible cover to project outward and then apply 

 the flame to the tip of the cover, gradually ]>ringing the flame under the crucible as 

 the reaction grown leii^s and less violent. The reaction is complete when fumes of 

 ammonia salts are no longer driven off. Intense ignition is unnecessary and is to be 

 avoided. The crucible should be weighed with its cover." 



The weight unit as the basis for calculating results of physical 

 analysis of soils, A. ]\IrrscHERLiCH {F'uhUixfti Lamhv. Zt(j.,Jt.9 [1900), 

 JTo. 7,j:>p. 259-265). — While the results of chemical analysis of soils 

 are usually calculated to the weight basis, it is frequently considered 

 desirable to calculate the results of physical analyses to the volume 

 basis. Two methods of doing this are described: (1) One-tenth liter 

 samples of the air-dried soil which has been put through a 1.5 mm. 

 round-hole sieve and as uniformly compacted as possible are weighed 

 and the moisture determined by drying over concentrated sulphuric 

 acid. From the data thus secured the volume weight is calculated. 

 (2) The specific volume is determined bj^ means of a picnometer in 

 the usual way, and the water capacity is determined by shaking up 

 the soil (in vessels of known capacity) with water so that the air is 

 completely displaced, the mass being allowed to stand and the excess of 

 water finally removed. The resvdts of these 2 determinations furnish 

 the basis for calculating the volume weight. From the results of tests 

 of these methods on a series of soils the following conclusions are 

 reached: The volume unit is not a safe basis for quantitative ph3^sical 

 investigations of the soil unless the specific volume is determined in 

 each case. For quantitative investigations the results may be calcu- 

 lated from a weight to a volume basis with negligible error by assum- 

 ing an average specific volume of 0.380, adding, in case of hunuis 

 soils, a correction obtained b}' multiplying the humus content by O.003. 



Determination of tannin and of gallic acid, F. Jean (Bev. Chim. 

 AnaJyf. ctAppL, 5 {1900), Xo. I^, pp. 13Jf-lJf,0).—T^hQ method is based 

 upon the following principle: When iodin solution is added to a solu- 

 tion of tannin or gallic acid, rendered alkaline with bicarbonate of 

 soda, the iodin forms with the astringent matter a soluble red com- 

 pound, while starch is not acted upon. Briefly stated, the method is as 

 follows: The total astringent material is first determined l^y titrating- 

 against the iodin solution. The tannin is next precipitated with albu- 

 min, and the remaining gallic acid titrated, a correction is made for the 

 albumin solution, and the tannic acid determined b}- difference. No 

 figures are given showing comparative results with other methods. — 



H. SNVDER. 



Trials of some methods for cellulose determination, C Beck 



{Ztschr. TJntersxLch. JSfahr. n. (rcnxsxhitJ., o {1900), Xo. 3, pj). 158- 

 IGIi). — From tests of Le])l)iirs hydrogen-peroxid method (E. S. R., 8, 

 p. 857) and Konig's glyccrin-sulphuric-acid method (E. S. R., 10, p. 

 411) in comparison with the Henneberg (Weende) method, the author 

 concludes that Lebbin's method ''has neither scientific nor practical 



