122 EXPERIMENT STATION RECORD. 



[Studies of changes which take place in nitrogen when added to soils 

 in different forms of combination], W. A. Withebs (Xorth Carolina Sta. lipt. 

 1906, pp. 15-18). — This is a brief summary account of the work of the year in 

 the chemical department of the North Carolina Station which dealt mainly with 

 the changes which nitrogenous matter undergoes in the soil, and is a continua- 

 tion of previous work along the same line ( E. S. R., 17, p. 344). The nitroge 

 nous compounds experimented with were asparagin, ammonium sulphate, sodium 

 nitrite, and sodium nitrate. When these materials were mixed with sterilized 

 soil and immediately extracted by shaking with water for 4 hours about 88 per 

 cent of asparagin and of ammonium sulphate, 92 per cent of sodium nitrate, and 

 only 59 per cent of sodium nitrite were recovered. 



The colorimetric method for the determination of nitrites, proposed by the 

 Bureau of Soils, was used in these investigations. As a means of decolorizing 

 the nitrite solutions lampblack extracted with alcohol or gasoline was found to 

 be satisfactory as was also the treatment with ammonia and alum combined, 

 the alum being used in excess. 



In soils with or without addition of the nitrogenous compounds nametl there 

 was no production and some reduction of nitrates or nitrites during February 

 but a considerable formation in September. At the latter period the soil treated 

 with asparagin produced nitrites but no nitrates and that treated with ammo- 

 nium sulphate produced nitrates but no nitrites. The conclusion is therefore 

 reached " that the oxidation of organic nitrogen and of ammoniacal nitrogen is 

 accomplisheil by different organisms." 



Other observations are reported which indicate that nitrifying organisms are 

 readily transferred from the soil of one pot to that of another by natural agen- 

 cies. Apparently the nitrous organism is more resistant than the nitric oi'gan- 

 ism but less resistant than the reducing organism. Other lines of work which 

 are in progress or contemplated are briefly referred to. 



The interaction of ammonium salts and the constituents of the soil, A. 1». 

 Hall and C. T. Gimi.ngham {.Jour. Chrni. i<oc. [London]. 91-!)2 (HJOl). \o. .)3.'i. 

 pp. 6'77-687). — In view of the observation that the application of neutral am- 

 monium salts, such as sulphate and chlorid. has resulted in the production of an 

 acid reaction in soils, the authors undertook the investigations which are here 

 reported to determine the actual effects which are produced when dilute solu- 

 tions of ammonium salts are brought in contact with the separate appi-oximate 

 constituents of soils, viz, sand, clay, humus, and calcium carbonate. The method 

 of procedure was, in general, to shake 100 gm. of dry material for 24 hours with 

 a solution of 3ft(t cc. of a solution of ammonium salts, then to determine whether 

 there had been any increase in acidity or evolution of ammonia. 



The trials with sand gave absolutely negative results and are not reported. 

 In the case of clay there was no change of reaction and no withdrawal of the 

 acid radicle from the solution. The reaction of the ammoniimi salts on the clay 

 was apparently purely one of double decomposition. Complete absorption of 

 the base did not occur even when as much as 50 gm. of clay to 1.6 gm. of am- 

 monium chlorid was used. Much the same results were obtained with am- 

 monium carbonate and phosphate as with ammonium chlorid. 



In the case of the phosphate and carbonate, some of the acid was also removed 

 from solution. It was observed that when ammonium salts were used in e.\cess 

 of the clay, reaction proceeded until a definite point was reached and then 

 stopped, " so that a given weight of clay removes the same amount of ammonium 

 from solution, whatever the strength of the solution of ammonium salt with 

 which it is in contact." It was found that when varying quantities of clay 

 were shaken with fifth normal and tenth normal .solutions of ammonium chlorid, 

 100 gm. of clay withdrew approximately 0.147 gm. of ammonium from solution. 



