Determination of Iodine in Blood and in Animal Tissues

Although the refinements outlined in the previous paper permit the determination of minute amounts of iodine, the method cannot be applied directly with blood and tissues because the iodine content of 0.5 gm. or even 1 gm. of the material is much too small to be detected.However, the only additional requirement to the method is the destruction of a large amount of organic matter without loss of iodine.The first attempt was to hydrolize the proteins of blood and tissue with 5 per cent sodium hydroxide in an autoclave at 200".The solution was acidified and filtered.Attempts were then made to distill the iodine from the solution after the addition of an oxidizing agent.For this purpose chromic acid, copper, iron, and-arsenic were tried, and it was found that although the iodine was liberated it was not quantitatively distilled.The next attempt to destroy the organic matter was by means of a fusion with nitrate.This resulted in excessive heating, the organic matter frequently igniting.As this was always accompanied by loss of iodine, it was found impracticable to destroy the organic matter with oxidation.Attempts were then made to remove the organic matter simply with a destructive distillation, and it was eventually shown t.hat in the presence of about 3 gm. of sodium hydroxide for each 100 gm. of blood or tissue the water can be evaporated on a hot plate and the organic matter destroyed at a temperature between 300-400" without appreciable loss of iodine.The char is extracted with water.The solution is dark brown and still contains a