1919] AGRICULTURAL CHEMISTRY — AGROTECHNY. 411 



foam breaker for use in the rapid aeration of blood and other fluids and is 

 much cheaper than caprylic or amy! alcohol. If the resin solution is not neu- 

 tral to alizarin, either N/10 sodium hydroxid or sulphuric acid should be 

 added to exact neutralization. 



The rapid estimation of perchlorates, alone, or in the presence of chlorates 

 and chlorids, J. G. Williams (Cheni. News, 119 (1919), No. 3090, p. 8).— The 

 method described is based on the oxidation of titanous chlorid by perchlorates 

 in the presence of sulphuric acid and the estimation of the oxidation by titration 

 of the cooled solution with ferric alum solution, using as an indicator two or 

 three drops of a 10 per cent solution of potassium thiocyanid. The method is 

 said to give a good degree of accuracy and to be much more rapid than the 

 fusion method. 



A method for the volumetric estimation of sulphates, A. C. D. Rivett 

 (Chem. Neirs, 118 {1919), No. 3085, pp. 253, 25 J,). — The method depends upon 

 the fact that moist precipitated barium oxalate reacts quantitatively with 

 soluble sulphates of certain metals to give barium sulphate and the soluble 

 oxalates of these metals. The latter may be titrated in the filtrate with 

 potassium permanganate. 



Tables are given showing the percentage error under different conditions, 

 from which the following limitations of the method are deduced : " It is In- 

 applicable in acid solutions, and can not be used to determine sulphates of 

 metals forming insoluble oxalates or sulphates in presence of salts containing 

 radicals capable of forming insoluble barium salts. The presence of halids is 

 objectionable in preventing accurate titrations with permangante. There will, 

 however, be many works solutions to which the method may be applied with 

 accuracy and considerable saving of time." 



The determination of phosphoric oxid, particularly in fertilizers, soil ex- 

 tracts, and the like, B. de C. Makchand (So. African Jour. Sci., 15 {1919), No. 

 5, pp. 357-363). — The method described, which is attributed to H. J. Vipond, is 

 a combination of von Lorenz's method of precipitation for ammonium phos- 

 phoiuolybdate (E. S. R., 13, p. 14) and Pemberton's volumetric method for the 

 determination of the precipitate (E. S. R.. 5, p. 444). 



Analytical data are presented from which the factor for conversion of cubic 

 centimeters of N/10 sodium hydroxid to grams of phosphoric oxid has been 

 found to be 0.000284 instead of O.00O3089 as used by Pemberton. 



The volumetric method is recommended for soil extracts and plant ashes, and 

 is thought to be capable of greater accuracy than methods such as that of 

 Neubauer (E. S. R., 17, p. 731), in which the phosphoric oxid is weighed as 

 magnesium pyrophosphate. 



A note by B. J. Smit on the recovery of ammonium molybdate from the 

 residues from the above method is appended. 



The determination of total nitrogen in soils containing rather large 

 amounts of nitrates, R. S. Snyder {kioil Sci., 6 (1918), No. 6, pp. JfS7-490). — 

 Determinations by various methods of the total nitrogen in soils containing 

 large amounts of nitrates, in soils originally containing no nitrates but to 

 which known amounts had been added, and in soils very low in organic carbon, 

 are reported. From the analytical data presented the following conclusions are 

 drawn : 



" Many soils have a high nitrate content (up to 10 per cent of the total nitro- 

 gen) and the recovery of this nitrate is necessary in total nitrogen determina- 

 tions. If the organic matter of the soil is within the usual average (0.8 to 3 

 per cent), it is not necessary to use the modified methods for total nitrogen, 

 the common unmodified methods (Hibbard or mercury) giving quite as accurate 

 results. Methods for total nitrogen, modified to include the nitrogen of nitrates, 



