Cccxvii. the Effect of Light on the Vitamin C of Milk.1

IN estimating vitamin C chemically in milk by the method of Birch et al. [1933], Kon [1933] observed very marked fluctuations in the concentration of that vitamin from day to day. The possible causes of this phenomenon were investigated by Mattick & Kon [1933], who ultimately found that milk which originally gave a positive vitamin C titration failed to reduce the indophenol reagent after a short exposure to light in glass bottles. Some time later Booth & Kon [1934] showed that 90% of the original power of reducing the reagent could be restored after short exposures to light by treating the milk with hydrogen sulphide. Longer exposure entailed greater irreversible losses. An example of the effect of light will be found in Table I.