Need for a Working-Factor in Evaluating Freezing Point Results on Raw Milk Samples ¹

The legal upper base for taking action in cases of water adulteration of milk is generally accepted as - 0.525°H. Henningson (2), in a study of 660 samples of milk known to contain no added water and representing 22 states in the U.S. and four Canadian provinces, found (at the 95% confidence limit) only 1% probability of a naturally-occurring milk sample falling above that level. Yet at a mean value of - 0.540°H, as noted in this same study, such base allows for 3% added water for the "average" dairy farm. The present study, made on samples without knowledge of their purity (lack of added water), tends to confirm this potential. At the same time it suggests the likelihood that, on a practical basis, a "working factor" set at some lower value could be useful to the dairy industry in coping with the problem of added water in milk.