. The Biochemical journal, 1917. Biochemistry. 266 J. C. DRUMMOND hydrochloric acid and extraction with the amyl alcohol-ether mixture recom- mended by van Slyke [1915]. Very incomplete decomposition was effected by this method, for a bulky flocculent precipitate, probably representing precipitated pigment, resisted decomposition. The aqueous fraction was separated after repeated extraction, filtered, neutralised and evaporated to small bulk at reduced temperature and Chart X. Curves 1-4. Basal diet + phosphotungstic acid precipitate fraction corresponding to 18 % "
. The Biochemical journal, 1917. Biochemistry. 266 J. C. DRUMMOND hydrochloric acid and extraction with the amyl alcohol-ether mixture recom- mended by van Slyke [1915]. Very incomplete decomposition was effected by this method, for a bulky flocculent precipitate, probably representing precipitated pigment, resisted decomposition. The aqueous fraction was separated after repeated extraction, filtered, neutralised and evaporated to small bulk at reduced temperature and Chart X. Curves 1-4. Basal diet + phosphotungstic acid precipitate fraction corresponding to 18 % "; Curves 5-8. Basal diet + phosphotungstic acid filtrate fraction corresponding to 18 % "; Chart X demonstrates that this fraction possessed a small growth pro- moting activity when administered in doses representing 6-18 g. of the original " ; Great loss had, however, occurred during the process. The filtrate from the phosphotungstic acid precipitation was freed from sulphuric acid and the excess of the precipitant by means of baryta and after concentration tested for activity. None however was observed (Chart X). Whether the active substance is completely precipitated by phospho- tungstic acid is uncertain, for any which was unprecipitated would be adsorbed and lost during the removal of the sulphuric and phosphotungstic acids by baryta, owing to the very bulky precipitate which results. Great loss also occurred without a doubt due to the adsorption of the active body by the flocculent residue of undecomposed phosphotungstates which has been already noted. A further preparation of the phosphotungstates from 200 g. of "marmite" was made, and Aveighed in the dry condition 90 g. This was treated when quite dry by shaking up with repeated changes of acetone [Funk, 1916]. A large proportion (69 g.) of the precipitate remained undissolved. It would seem probable from studies upon the solubilities of the phosphotungstates in acetone (no
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