20G 



EXPERIMENT STATION RECORD. 



[Vol.41 



III the study of soils associated with various plauts, tlio author has found 

 that certain more or less well-detiued types of reaction can be recognized as 

 follows : 



Superacid, bog peat supporting a characteristic flora of oxylophytes or acid- 

 soil plants ; mediacid, some bog peats, many upland peats, and other soils sup- 

 porting oxylophytes ; subacid, ordinary wood and field soils of low acidity ; 

 subalkaline, soils derived from limestone rocks; medialkaline and superalka- 

 line, soils in alkaline regions where free sodium carbonate occurs. 



Certain general advantages possessed by the proposed methods of stating re- 

 actions are discussed, the most desirable feature being the ease with which the 

 relative magnitudes of reactions under comparison can be appreciated. The 

 method is considered to be applicable to all determinations hitherto expressed 

 in terms of pH. 



A sim.plified wet combustion method for the determination of carbon in 

 soils, D. D. Waynic'k {Jour. Indus, (utd Eur/in. Chem., 11 (11)19), No. 7, pp. 

 634-637, fig. 1).—The author, at the California Experiment Station, has modi- 

 tied the apparatus usually used in the wet combustion method in such a way 

 that the carbon dioxide evolved is absorbed in soda lime and can be determined 

 gravimotrically. The reagents used are essentially those employed by Ames 

 and Gaither (E. S. R., 32, p. 805), except that the chromic acid soUition con- 

 tains 3.3 gni. in 5 cc. of water. This amount of chromic acid and 50 cc. of sul- 

 phuric acid are used for each combustion. 



The essential details of the apparatus are given in the accompanying figure. 

 The air enters the apparatus through A, a tube filled with calcium chlorid. 



R ^-.v-^ 



— 5f 



^^ 



VHfff: 





"^ 



Fig. 1. — Modified apparatus for the wet combustion metbod. 



It then passes through a column of 30-mesh soda lime in B and a small volume 

 of concentrated potassium hydroxid in C, the latter serving as a means of 

 ]vt>eping check on the rate of flow of air through the apparatus which is reg- 

 ulated by the stock-coclc of D. The dropping funnel D holds the sulphuric 

 acid before its introduction into the 300 cc. combustion fiask E. The first of 

 a series of three scrubbers F is tilled with glass beads wet with sulphuric acid. 

 This takes tlie i)la('e of the usual condenser and n^moves most of the sulphur 

 trioxid funu's coming from the combustion llask. The dilute sulphuric acid con- 

 densed in F is caught in a 100 cc. Erlenmeyer flask G connected with a second 



