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Evolution of the Original (Empirical) to the Present-day (Exact) Coirtposition.-O. Liining contributes the results of an inquiry into the gradual evolution of the originally simple, though empirical formula given by Fehling (1818), to that modernly insisted on, which requires great exactitude in the quantities of copper sulphate (34.639 gm.) and of sodium hydroxide (51.6 gm.) to the liter. By his original formula, Fehling simply endeavored to produce a stable solution, without reflecting upon the possible use of the reagent for the quantitative determination of glucose ; he directed that 40 gm. pure crystallized cupric sulphate be dissolved in approximately 160 gm. water, and to the cold solution the addition of 160 gm. potassium tartrate in 500 gm. caustic soda solution, sp. gr. 1.12 and sufficient water to make 1 liter at 15' C. But subsequently (1849), believing that 1 Mol. of sugar corresponds to 10 Mols. of cuprie sulphate, he recommended the further addition o,f water so as to produce 1154.4 cc. of the reagent, which possessed this relation to the sugar, and this soon led to the reduction of the cupric sulphate to 34.639 gm. in the formula producing the original volume of 1 liter. The author then interestingly describes the further evolution until the present formula, used almost universally, was adopted, this consisting, as is well known, of two solutions, t o be mixed in equal volumes as required, viz.: No. 1, 34.639 gm. Cupric Sulphate dissolved in water to make 500 cc.; No. 2, 51.6 N a O H (in 100 cc. Water) and 173.0 gm. Rochelle Salt in sufficient water t o make 500 cc. T h e author proves from the literature that the insistence on the fractions of copper sulphate and NaOH is not necessary. The quantities may be rounded off to 34 and 51 gm. respectively, and this should be done in the published formulas for this solution.-Apoth. Ztg., XXVII Fehlinp's Solution : (1912), NO. 10, 91-92.
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