The precipitation of the basic amino-acids of proteins with phosphotungstic acid

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Abstract
The precipitation of pure diamino-acids by phosphotungstic acid at various N concentrations is studied. At high N concentrations some proline is also precipitated, while lysine under the same conditions has a tendency to form a soluble double salt. From the precipitation curves obtained it is deduced that treatment of gelatin with acid increases the content of both lysine and proline. The solubilities of the phosphotungstates are given and the reasons for their variation discussed. Photomicrographs of the crystalline phosphotungstates are included.