Studies on the Iodine Content of Milk

Summary Samples of mixed milk of several herds at each of eight different points in South Carolina, were collected at intervals of three weeks, over a period of ten months (November, 1931, through August, 1932) and dried by the roller process. The cattle received only locally grown foods and feeds, and none were given iodized salt. Iodine estimations on the dried milk were made by the method of McClendon as modified by Remington, and also by von Kolnitz’ adaptation of the Karns technique, the latter method proving shorter and more workable, besides giving about 10 per cent higher recoveries. The average iodine content of the 117 samples was 572 ± 16 parts per billion, dry basis. Averages for two points in the coastal plain (Bamberg 353 ± 18, Cheraw 411 ± 12) were significantly lower than for six points in the Piedmont (Abbeville 712 ± 38, Chester 573 ± 35, Gaffney 548 ± 26, Greenville 744 ± 71, Newberry 545 ± 39, and Winnsbora 684 ± 55). Values obtained in April and May were slightly but significantly lower than for the remainder of the period. During the same period nine samples taken at a commercial milk drying plant in New York, and six samples at one in Wisconsin, averaged respectively 265 ± 24, and 322 ± 22; and seasonal variations were much greater than for the South Carolina samples.