[909] 



DACHNOWSKI— BOG TOXINS 



395 



f Mr. C. H. Kerr of the Carborundum Company, 

 New York. They are among the most insoluble sub- 

 stances known, and of great purity, which makes them of special 



The chemical analysis of these materials 



value in this investigation. 

 is as follows : 



TABLE II 



Material 







C 



, 



Si 



Si0 2 



Al,0 3 



CaO 



Fe 2 3 



K 2 



MgO 



-Va,0 



Ignition 



Quartz 



Kaolin 



99 -5 6 



0.40 



* - 



o. 14 



45-35 



38.86 



°-35 

 0.38 



0.61 



0.31 



0.31 



13 



Carborundum 



.80 



29.71 



o-45 

 69.40 



0.28 



O.K 



O.O5 



The physical composition of the materials employed was deter- 

 mined by microscopic examination. Mechanical analysis was made 

 with the aid of a centrifuge and for the coarser components by means 

 of their different rates of subsidence in water. The relative percent- 

 ages by weight of the different component particles in each group is 

 as follows : 



TABLE III 



Material 



Sand 



°-5"~0.25mm. . 



x e *y fine sand 



su? I ~ 005mm - - 



O.05 — 0. oosmm 



Clay ° 



O.005 — O.O m m. 



SiO« coarse 



100 



ft ft 



ft V 



SiOa fine 



Kaolin 



SiC 



6.5 



80.8 



12.9 



♦ • 



2.4 



61.8 



35-7 



79-4 

 16.6 



4-5 



To obtain the surface area of spherical particles it is only neces- 

 ^y to invert the value of the mean diameter of the particles 

 or each group. This surface factor is then multiplied by the frac- 

 tal amount of the 

 ^an diameters. A 

 quartz fl our, carborundum, or other crystalline bodies with irregular 



sam 



mathematical 



