302 EXPERIMENT STATION EECOED. 



liydroxystearic acid, CisHaeOa; parafBnic acid, C24H4s02; liguoceric acid, C-ilLsOa; 

 phytosterol, C26H440.H.,0 ; pentosan, CsHsO* ; liistidin,C6H902N3 ; arginin, C6H14O2N4; 

 cytosin, C4H5ON3.H2O ; xantbin, aH402N4 ; liypoxantliin, C5H4ON4 ; fatty glycerids 

 and several resin acids and esters. 



" The conclusion is reached that while the worli here reported shows the 

 complex character of the organic matter of soils, this complexity is not so 

 great that the chemical nature of all of the organic matter of soils can not be 

 determined by modern methods of research." 



A schematic representation of the methods utilized for separating and isolating 

 the above bodies is given. See also a previous note (E. S. R., 20, p. 919). 



Studies of the ammonia-soluble organic matter of the soil, G. S. Fraps and 

 N. C. Hamnee (Texas Sta. Bui. 129, pp. l--i9). — The first section of this work 

 deals with a comparative study of methods for estimating the humus in soils. 

 The authors use the term " humus " in this paper for convenience in desig- 

 nating the ammonia-soluble organic matter, but do not mean to subscribe 

 thereby to any theory which concerns the importance of the ammonia-soluble 

 material. 



A comparison between the official method (E. S. R., 19, p. 506) and the 

 Snyder method (E. S. R., 5, p. 857; 7, pp. 477, 484; 9, pp. 632. 641; 16, p. 956) 

 showed that the latter gave lower results on igniting the extract but that the 

 solution contained more clay (ash). Correcting by the Peters-Averitt method 

 (E. S. R., 18, p. 114) by subtracting 10 per cent of clay showed the Snyder 

 method to give the lower results of the two, from which the authors conclude 

 that " a correction of the loss on ignition by subtracting 10 per cent of the ash, 

 as proposed by Peters and Averitt, is better than no correction." 



The authors consider that the selecting of a method for this work is greatly 

 dependent upon its ease of execution. The official method has the advantage of 

 bringing less clay into suspension and apparently extracts just as much organic 

 matter (or more) as the Snyder method. On the other hand, when utilizing 

 this method for heavy clay soils gumming occurs and a long time is required 

 for the extraction process. " Filtration through unglazed porcelain removes 

 the clay, but a portion of the organic matter may not pass through. The clay 

 may be precipitated by means of various salts, such as ammonium sulphate or 

 chlorid and sodium sulphate or chlorid." A further study is to be made of the 

 electrolytic method for removing the clay. It was also noted that '" evaporation 

 and solution of the residue in ammonia as proposed by Mooers (E. S. R., 19, 

 p. 714) appears to be the most promising method for the estimation of humus. 

 Precipitation with acid, as is to be expected, removes only a portion of the 

 dissolved organic matter. The average recovery is 64 per cent. Extended 

 washing with acid increases the quantity of ash in suspension but has little 

 effect on the organic matter. Strong ammonia extracts more organic matter 

 than dilute ammonia. This is evidence that material goes into solution which 

 is not ' ammonium humate ' but is merely organic matter soluble in ammonia, or 

 converted by it into soluble compounds." 



Part 2 treats of the formation of ammonia-soluble oi'ganic matter in the soil, 

 and shows that " organic matter added to the soil already contains ammonia- 

 soluble material. When no correction is made for the ammonia-soluble sub- 

 stances in the added material, ammonia-soluble humus is apparently formed in 

 the decay of cotton-seed meal, etc., but when correction is made for the added 

 ammonia-soluble material the ammonia-soluble material is found to decrease. 

 The least loss of organic matter takes place with a soil containing water equal 

 to 77 per cent of its saturation capacity." 



Section 3 deals chiefly with the composition and properties of the precipitated 

 liumic acids as prepared from various soils. 



