In several cases the method has been applied to milk products which were also assayed for riboflavin by means of chicks. The chick assays upon six samples gave an average value of 21.2 micrograms per gram. An average value of 21.5 micrograms per gram was obtained by the photometric test. The method presented in this paper is preferred because of its rapidity, and because biological assays may be complicated at times by the presence or absence of nutritional factors which are not as yet clearly defined.

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A detailed study has been made of the Denigbs colorimetric method for phosphorus. The concentrations of reagents at which phosphomolybdate gives a maximum

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