The foregoing conclusions have been strikingly confirmed by experiments with maceration extract carried out by Euler and Johansson [1913], in which both the carbon dioxide evolved and the phosphate rendered non-precipitable by magnesia were determined at intervals. When dried yeast is employed as the fermenting agent, the amount of phosphate esterified in the earlier stages is greater than would be expected, but ultimately becomes exactly equivalent to the carbon dioxide evolved. NATURE OF THE PHOSPHO-ORGANIC COMPOUND FORMED BY YEAST-JUICE AND ZYMIN FROM THE HEXOSES AND PHOSPHATE. The formation and properties of the compound produced from phosphates in the manner just described have been investigated by Harden and Young [1905, 2; 1908, 1; 1909; 1911, 2], Young [1909; 1911], Iwanoff [1907; 1909, 1], Lebedeff [1909; 1910; 1911, 5, 6; 1912, 3; 1913, 1]; and Euler [1912, 1; Euler and Fodor, 1911; Euler and Kullberg, 1911, 3; Euler and Ohlsén, 1911; 1912; Euler and Johansson, 1912, 4; Euler and Bäckström, 1912], but its exact constitution cannot as yet be regarded as definitely known. [p048] Phosphates undergo this characteristic change when the sugar undergoing fermentation is glucose, mannose, or fructose, and it may be said at once that no distinction can be established between the products formed from these various hexoses; they all appear to be identical. The compound produced is, as already mentioned, not precipitated by ammoniacal magnesium citrate mixture, nor by uranium acetate solution. It can, however, be precipitated by copper acetate (Iwanoff) and by lead acetate (Young). The preparation of the pure lead salt from the liquid obtained by fermenting a sugar with yeast-juice or zymin in presence of phosphate is commenced by boiling and filtering the liquid. Magnesium nitrate solution and a small quantity of caustic soda solution are then added to precipitate any free phosphate, and the liquid well stirred and allowed to stand over night. To the neutralised filtrate lead acetate is then added together with sufficient caustic soda solution to maintain the reaction neutral to litmus, until no further precipitate is formed. The liquid is then filtered or, better, centrifugalised, and the precipitate repeatedly washed with water until a portion of the clear filtrate gives no reduction when boiled with Fehling's solution. It is essential that this washing should be thorough as evidence has recently been obtained of the formation under certain conditions of a hexosephosphate, the lead salt of which is not so sparingly soluble as that of the hexosediphosphate [Harden and Robison, 1914]. The lead precipitate is then suspended in water, decomposed by a current of sulphuretted hydrogen, the clear filtrate freed from sulphuretted hydrogen by a current of air, and finally neutralised with caustic soda. The removal of phosphate and conversion into lead salt are repeated twice, and the