INORGANIC COMPOSITION OF SOME AMERICAN SOILS. 5 



When received at the laboratories the sample was spread on brown 

 wrapping paper and allowed to air-dry. It was then passed through 

 an iron sieve of 6 meshes to the linear inch. The soil clods not 

 passing were crushed with a wooden rolling-pin on brown paper and 

 passed through the sieve. The stones, sticks, roots, etc., were 

 rejected. 



The soil passing through the sieve was well mixed and quartered 

 down to a subsample of 7 to 10 pounds. This was crushed in an 

 iron mortar to break up the larger soil particles, such as iron and 

 manganese concretions and the like. It was then quartered down 

 to a sample of 50 grams, which was ground till it passed entirely 

 through a silk bolting cloth of 100 meshes to the linear inch. 



In this work of subsampling and grinding great care was taken, 

 for it was recognized that in some cases the rarer elements were 

 segregated in comparatively large pieces of their mineral species. 

 For instance, manganese is often found in large concretions and 

 zircons occur in fairly large, hard crystals. If such samples were 

 not carefully ground and mixed, that portion taken for analysis 

 might contain an undue number of these crystals or concretions. 



NOTES ON THE METHODS OF ANALYSIS. 



For the determination of the major constituents the soil was first 

 ignited to destroy organic matter, then fused with sodium carbonate, 

 following the procedure outlined by Hillebrand. 1 Where there were 

 choices of different methods or special difficulties encountered, varia- 

 tions were adopted. Notes explaining these points are given below. 



IRON AND ALUMINUM. 



Generally soils are higher in iron and aluminum than rocks and 

 contain but little manganese and comparatively small quantities of 

 calcium and magnesium. The precipitate of the iron and aluminum 

 group, obtained by the use of sodium acetate, is difficult to handle 

 when large, and has a tendency to run through the filter. Although 

 this part was filtered off when the filtrate from the iron group was 

 concentrated, the precipitate of the calcium oxalate contained much 

 more iron and aluminum than when the iron group was precipitated 

 with ammonia. Accordingly precipitation of this group was made 

 with ammonia. Manganese may have been present in the iron 

 group precipitate, but in small quantity only, for nearly all was 

 recovered in the ammonium sulphide precipitate, as shown by a 

 comparison of the amount obtained in this way with the total amount 

 determined by the use of hydrofluoric aci-d on another sample of the 

 soil. 



i Bui. 422, U. S. Geol. Survey (1910). 



