In a method for spectrophotometric determination of ergosterol in yeast samples containing 5 to 100 mg. of yeast solids, the yeast is digested with alcoholic alkali and ergosterol is extracted in a single extraction with a measured volume of pure n-heptane. Absorbances at 281.5 and 230 µ are determined on an aliquot of the heptane diluted in absolute ethyl alcohol. Amount of "ergosterols" are determined from the 281.5-µ measurement, and amount of 24(28)-dehydroergosterol is determined from the 230-µ measurement.

ated meat samples. At lower temperatures, the time required to ebulliate all the mercaptan was too long for convenient routine assay. At higher temperatures, the possibility of inaccurate high values as the result of protein degradation appeared likely.A series of experiments was run to determine the effect of short storage periods on the volatile methyl mercaptan content of irradiated beef. No significant difference in the amount of methyl mercaptan was noticed within 36 hours after irradiation, if the irradiated samples were stored in the frozen s:ate at -18°C.Thus, as long as the irradiated samples were kept frozen, methyl mercaptan could be quantitatively determined within 36 hours after irradiation.On the basis of methyl mercaptan determinations on a large number of irradiated-meat samples, the methyl mer-captan content of beef increases directly with gamma-irradiation dosage (Table III). In addition to this dosage effect, there is a difference in the amount of methyl mercaptan formed in different samples of beef during irradiation. Literature Cited(1) Almv, L. H., J. Am. Chem. Soc. 47, 1381-90 (1925).

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