1919] 



AGRTCULTURAL CHEMISTRY — AGROTECHNY. 



205 



routine work of testing fresli supplies of clieiuicals for the impurity, and in 

 very accurate work of conducting a control experiment during each determina- 

 tion of albuminoid ammonia. 



The gravimetric determination of sulphate as barium sulphate, I. M. Kol- 

 THOFF and E. H. Voijelenzang {Pharm. Weckbl., 56 {1919), No. 5, pp. 122-142; 

 ahfi. in Chein. Abs., 13 (1919), No. 9, p. 944)- — Tlie various sources of error in 

 the determination of sulphate as barium sulphate are discussed from the liter- 

 ature on the subject and from experiments conducted by the authors. The fol- 

 lowing conclusions are drawn : 



The solubility of barium sulphate (2.3 mg. per liter at room temperature) h- 

 greatly increased by higher temperature. The presence of nitric or hydrochloric 

 acid also increases the solubility of barium sulphate. This is more marked 

 with nitric than with hydrochloric acid. Dry ignition in porcelain or moist 

 ignition in platinum causes little or no reduction, dry ignition in platinum con- 

 siderable reduction. The precipitate should be moistened with sulphuric acid 

 and ignited to constant weight. Occluded salts can not be washed out after 

 ignition as the occlusion is chemical in nature. The error due to phosphates is 

 caused by the formation of barium phosphate from the barium sulphate. It is 

 impossible to prescribe a general method of procedure for the accurate determi- 

 nation of sulphates in any particular solution. 



The determination of sulphate as strontium sulphate, I. M. Kolthoff and 

 E, H.. VOGELENZANG (Phurtn. Weekhl, 56 (1919), No. 6, pp. 159-161; abs. in 

 Chem. Abs., 13 (1919), No. 9, pp. 9U, 9^5).— The determination of sulphate as 

 strontium sulphate is shown to be subject to the same errors as in the case 

 of barium sulphate noted above. While alcohol decreases the solubility of stron- 

 tium sulphate alone, free acids and certain salts act as disturbing factors. A 

 table is given showing this influence. 



The statement of acidity and alkalinity with special reference, to soils, 

 E. T. Wherry (Jour. Wash. Acad. Sci., 9 (1919). No. 11, pp. 305-309) .—The 

 author proposes a method of stating acid and alkaline reactions in terms of 

 so-called " specific acidity " and " specific alkalinity " the unit of which, instead 

 of being 1 gram-equivalent per liter as in the usual method, is the number of 

 gram-equivalents per liter of each ion present in pure water at ordinary tem- 

 perature. The table given below, an abbreviation of the one given in the original 

 article, shows the actual numbers corresponding to the powers of 10 representing 

 some of the reactions likely to be met with in soil. The new values are called 

 chemical potentials, and at the suggestion of E. Q. Adams are given the letter 

 X, the Greek initial of chemical. 



Comparison of different methods of stating reactiotis. 



1P.268S''— 19- 



