279. The estimation of lactose in milk

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Abstract
1. The direct volumetric copper reduction method of estimation of lactose in unclarified milk gives results which are in good agreement with those on the same milk clarified and decalcified. 2. For the polarimetric' or iodometric methods of estimation of lactose the milk is best clarified with either zinc hydroxide or cadmium hydroxide. Clarification with acid mercuric nitrate or phosphotungstic acid for the polarimetric method and with dialysed iron or phosphotungstic acid for the iodometric method gives high results owing to failure to remove interfering substances. 3. Dialysed iron, phosphotungstic acid, cadmium hydroxide or zinc hydroxide are all suitable for deproteinizing the milk for the chloramine-T method of estimation of lactose. 4. The values for lactose content of milk as estimated by the above methods show good agreement and therefore may be accepted as the true milk sugar content.