BOOKS AND CURRENT LITERATURE 



95 



be i^recipitated at the center of the field by an acid medium, wliile sugars 

 are diffused outward. 



A conception of the nature of this method of analysis is most readily 

 given by Griiss' description of its application to a solution containing 

 salts of nickel, cobalt and iron. A drop of the concentrated compound 

 solution is placed at the center of the capillarizer and widening of the 

 zones is checked by rapid evaporation. A drop of ammonium hydroxid 

 is then- added, which precipitates iron hydroxid at the center of the field 

 while the other metals are washed into a narrow outer zone. The addi- 

 tion of ammoniacal potassium nitrite solution to this zone holds cobalt 

 as the insoluble potassium cobalto-nitrite while nickel diffuses still 

 farther outward. Identification tests are applied as follows: To the 

 central field is added hydrogen peroxide (to oxidize the iron) followed by 

 potassium ferrocj'anide which gives the blue ferric ferrocj'anide. Acetic 

 acid causes the formation of the yellow potassium cobalt i-nit rite in the 

 median zone and diacetyl-dioxime precipitates a red compound of nickel 

 in the outer zone. 



In capillary analysis of enzymes it is necessary to apph' tests to the 

 various zones upon the paper in order to confirm the presence of specific 

 substances. For this purpose the paper is cut into sectors after capil- 

 larization and the sectors are applied separately to filter papers impreg- 

 nated with solutions of the various reagents or to glass plates coated 

 with starch paste, starch grains, or sections of cellular tissue. The 

 starch grains and tissue sections maA' be examined microsco])ically for 

 corrosion, and appUcation of iodine solution to the paper after treatment 

 with starch gives indication of the distribution of hydrolyzing activity. 

 Griiss used the following additional reagents for enzymes: Guaiac, 

 turned blue by oxidases and peroxidases; ursol tartrate, slate-blue with 

 peroxidase; 'Siolamin" (a benzene derivative), violet with bodies releas- 

 ing molecular oxygen, as well as by oxidizing enzjones (colored by hjxlro- 

 gen peroxid, it was used as a test for antioxidase or reductase) ; carminic 

 acid, decolorized by hydrogen peroxid, red with antioxidase. Sectors 

 bearing color reactions can be reunited to give a "chromogram" showing 

 the relative actiAity of the enzjines and their disposition in the different 

 zones. The volume contains two colored plates illustrating such chro- 

 mograms. Tests for an enz^-me present onlj' in minute quantity may be 

 strengthened by extracting its zone with water and recapillarizing on a 

 second paper, a process designated as "secondary capillarization." 



Having found capillary analysis of the cell sap of cereal embryos 

 impracticable, Griiss applied color tests directly to the tissues, with the 



