612 EXPERIMENT STATION RECORD. [Vol. 36 



(1: 1). The evaporation is completed on a sand bath and the residue ignited at 

 hhist-Iamp temperature to convert, the iron and alumimun salts present into 

 the insoluble oxids. The residue is treated with 25 cc. hot water, washed by 

 decantation, and finally on the filter until free from sulphates. The filtrate is 

 then evaporated to about 50 cc. volume and, after making the solution alkaline 

 with ammonium hydrosid, the calcium is precipitated in the boiling solution by 

 a saturated solution of ammonium oxalate. After allowing to stand for at least 

 three hours the solution is filtered and reprecipitated according to the official 

 method for determining calcium in soils. The filtrate and washings from 

 the calcium determination are evaporated to dryness, the ammonium salts re- 

 moved, and the potash determined according to the official Liudo-Gladding pro- 

 cedure (E. S. R., 20, p. 512). 



Comparative analytical data submitted indicate the accuracy of the pro- 

 cedure. 



Advantages claimed for the new method are a considerable saving of time, 

 the rapid removal of soluble salts from the iron and aluminum precipitate by 

 hot water, and the regulation of the amount of reagents used, thus avoiding 

 their removal later in the procedure. 



The ammoniacal nitrogen of peats and humus soils, J. C. B. Ellis and C. G. 

 T. MoRisoN (Jour. Ayr. Hci. [England], 8 {191G), No. 1, pp. 1-6). — The authors 

 have found that distillation with magnesium oxid by a slightly modified pro- 

 cedure, described in detail, yields fairly constant results for ammonia with the 

 same sample of peat. This amount is many times greater than that yielded in 

 the case of arable soils. Much of the ammonia can be removed by water alone, 

 but no constant ratio has been found between this amount and that obtained by 

 direct distillation. The.se respective amounts may vary considerably with the 

 depth from which the sample is obtained. 



The nature and source of this ammoniacal nitrogen and the conditions of its 

 solubility in the soil water are being studied. 



The reaction between dilute acids and the phosphorus compounds of the 

 soil, E. J. Russell and J. A. Prescott (Jour. Agr. Set. [England'], 8 (1916), 

 No. 1, pp. 65-110, figs. 20). — The extraction of phosphorus from soils by acids 

 and the adsorption of P2O5 in the presence of acid are discussed in some detail. 

 Experimental data obtained by the extraction of soils with dilute nitric, hydro- 

 chloric, sulphuric, and citric acids are submitted in graphical form. The effect 

 of the time of extraction, strength of acid, and temperature were also studied. 



When a soil is shaken with a dilute acid in the process of analysis " the acid 

 dissolves out such phosphorus compounds as it can, and different acids have 

 much the same effect at equivalent concentrations ; nitric, hydrochloric, and citric 

 acids give the same results ; sulphuric acid, however, gives a somewhat higher 

 result. A reverse reaction at once sets in, however. Some of the PjOs is 

 withdrawn from the solution in spite of the presence of excess of acid. The 

 process is an ordinary adsorption and obeys the usual law. ... Its extent 

 varies with the different acids ; it is much more marked in the presence of nitric 

 than of citric acid." The amount of phosphoi'us actually determined in a soil 

 extract is, then, not the true amount dissolved but the difference between the 

 two wholly distinct actions. 



This reverse reaction explains why the " available P2O5" determined by ex- 

 traction with dilute acids shows such variations in different metiiods of analy- 

 sis and so little correlation with the actual quantities used by the crops. The 

 results indicate nothing definite but simply a difference between a direct action 

 and an adsorption which varies with the nature of the acid and the conditions 

 of the experiment. 



