AGRICULTURAL CHEMISTRY AGROTECHNY. 807 



alone; iieuce koji must coutaiii some other kind of diastase wliicli produces 

 glucose directly from starch without the aid of glucase. Common salt has a 

 protecting action on koji-diastase under heating but not on malt-diastase, while 

 jS'a2HP04, asparagin, and H2SO4 impair its activity more quickly. The inhib- 

 itory action of salt on koji-diastase has a certain relation to the concentration 

 of diastase. In a dilute enzymic solution it is very strong but not in a con- 

 centrated enzymic solution. It is therefore necessary in every case to note the 

 concentration of diastase when we consider the inlluence of some salt uix)n it. 

 The activity of koji-diastase is conserved in brine for a long period." 



The determination of nitrogen in organic substances, IIeuzfeld {Pharm. 

 Ztg., 57 {1912), No. 97, pp. 979, 980; abs. in Chem. Ztg., 37 {1913), No. 14, 

 Repert., p. 58). — The organic material is treated with metallic potassium, taken 

 up with water, ferrous sulphate added, heated gently, and filtered. A contact 

 test is then made with a slightly acidified (HCl) ferric chlorid solution. At the 

 juncture of the two fluids a blue coloration appears if nitrogen is present. 



The colloid matter of clay and its measurement, H. E. Ashley ( U. S. Gcol. 

 Sin>v€y Bill 388 {1909), pp. 65, pi. 1, figs. 9). — In this paper clay is defined as 

 a mixture of granular matter and a colloidal gel. The sources of the colloidal 

 matters are organic and inorganic substances. The organic source resembles 

 peat, while the inorganic is principally colloidal silicates and silicic acid, and 

 less commonly alumina and ferric oxid. 



Adsorption, which is the property that colloids have of taking up other sub- 



stanc3S out of a solution or suspension, may in most cases be represented by 



exact equations. The plasticity of a clay may be measured approximately by 



the adsorption of a dye. " The plasticity, taken as the product of the deform- 



CXB, 

 ability by the force resisting deformation, reduces to the expression — 7^ 



where C is the measure of colloids present, B is the cast air shrinkage, and A 

 is the Jackson-Purdy surface factor. 



" TJie dye test supplies a measure of the efficiency of grinding in increasing 

 the plasticity of a fire clay. Questions that call for further study are the 

 possible finding of a better dj'e than malachite green, the disturbing influence 

 of minerals and salts in clays, and the formulation of a field test for plasticity." 



About the determination of colloid substances in the soil, Rohland 

 (Landw. Jalirh., Jf2 {1912), No. 2, pp. 329, 330).— It is stated that the method 

 described above, with some modifications, can eventually be employed for 

 determining the colloids in the soil. The colloids as such in the soil regulate 

 the passage of water and nutrient material to the plant and retain deleterious 

 substances. 



A contribution to the estimation of colloids in soils, I, M. G6bski {Ztschr. 

 Landw. Versuchsiv. Ostcrr., 15 {1912), No. 11, pp. 1201-1216, figs. 2).— It was 

 found that crystal violet can be used as an adsorption dye for colloidal sub- 

 stances. It was strongly adsorbed by soils, and when brought into contact 

 with soils does not alter its shade, which is considered an important ad- 

 vantage. The estimation of the dye was made colorimetrically by the Konig, 

 Hasenbaumer, and Hassler methods. Some preliminary experiments conducted 

 in regard to the behavior of crystal violet toward ferric and aluminum hy- 

 diK)xid showed that crystal violet was not adsorbed by either substance. 



In a chemical study of van Bemmelen's method 3 different kinds of soils 

 were used. The adsorption capacity of crystal violet was measured with the 

 3 soils, and proved Freundlich's equation correct. A comparison of the van 

 Bemmelen and the staining methods seemed to show that a parallelism exists 

 between them. 



46465°— No. 9—14 2 



