412 EXPERIMENT STATION RECOED. 



pennit one to run several determinations within a reasonable length of 

 time. ... 



" It was found, from a comparison of methods, that the amount of ammonia 

 'extracted by hydrochloric acid from soils is within the limits of our experi- 

 ments, independent of the strength of the acid and the period of extraction. 

 In the five soils tested hydrochloric acid removes approximately from 60 to 70 

 per cent of the ammonia added. The Folin aeration method can advantageously 

 be applied directly to the hydrochloric acid extract. The amounts of ammonia 

 obtained by distillation of the soil directly with magnesia is dependent upon 

 the duration of the distillation. The Steel method of aeration [E. S. R., 24, 

 p. 703] is not suitable for the determination of ammonia in soils. The Steel 

 reagents slowly decomjiose acetamid. 



" The Folin method of aeration is suitable for the determination of am- 

 monia in soils, for the same result is obtained whether the reagent acts for a 

 shorter or longer period, and all added ammonia is recovered." " The digestion 

 is carried out in the usual way, and the aeration conducted in much the same 

 way as Kober recommends. . . . 



" In the soils tested there is no interference through formation of triple 

 phosphate. There was no advantage found in using sodium chlorid with the 

 sodium carbonate. Acetamid is not decomposed by 4 per cent sodium car- 

 bonate. The results for ammonia obtained by examination of the hydro- 

 chloric acid extract are lower, while the results obtained by direct dis- 

 tillation of the soil with magnesia are higher, than those obtained by the aera- 

 tion method. The high results obtained by the former method are due to 

 occlusion of the ammonia by the soil, the nature of which is not clear, and 

 the lower results by the latter method are due to a partial decomposition of 

 the organic material by the magnesia to give ammonia." 



See also previous notes by Kelley and McGeorge (E. S. R., 30, pp. 419, 420). 



Solubility of calcium, phosphates in ammoniuni citrate solution, T. 

 Wabynski and J. Langel (Ann. Chim. Analyt., 19 (1914), No. 1, pp. 1-6; abs. 

 in Jour. Chem. Soc. [London^, 106 {1914), No. 617, II, p. 216).— In view of the 

 fact that mono-, di-, and tri-basic calcium phosphates are soluble in both water 

 and ammonium citrate solution to some extent, the method in use for separat- 

 ing these salts, which depends on the insolubility of di-basic and tri-basic 

 calcium phosphates in water, yields only approximate results. The solubility 

 of the salts in ammonium citrate solution reaches an equilibrium in about one 

 hour at 30° C, but this is not strictly the case with fertilizers where the phos- 

 phates may be enveloped by other substances. A better separation may be 

 obtained by treating the phosphates for one hour with a cold saturated am- 

 monium citrate solution. The solubility of the mono- and tri-basic phosphates 

 varies with the concentration of the citrate solution and reaches a maximum 

 with a concentration of from 10 to 15 per cent. 



Separation of calcium from magnesium, F. Halla {Cliem. Ztg., 3S (1914), 

 No. 10, p. 100; ahs. in Jour. Chem. Soc. [London], 106 (1914), No. 611, II, p. 

 219). — The following method is recommended for the separation of very small 

 quantities of calcium in the presence of large amounts of magnesium : 



" The neutral solution containing the chlorids of the two metals is heated to 

 boiling, and solid ammonium oxalate is added until the magnesium oxalate, 

 at first precipitated, redissolves ; the calcium oxalate remains insoluble. After 

 a few hours, the calcium oxalate is collected on a filter, washed with hot water, 

 then with cold water, ignited, sulphated, and weighed as calcium suli)hate. 

 The magnesium oxalate may be precipitated from the filtrate by the addition 

 of acetic acid." 



