208 abstracts: biological chemistry 



BIOLOGICAL CHEMISTRY.— Further experiments upon the deter- 

 mination of iodine in thyroid. Atherton Seidell, Hygienic 

 Laboratory, Public Health and Marine Hospital Service. Journal 

 of Biological Chemistry, 10: 95-108, Oct. 1911. 



In this paper are presented the results of an extensive series of analy- 

 ses made for the purpose of comparing the Hunter (J. Biol. Chem., 

 7: 321-49. 1910), and Baumann methods for the determination of 

 iodine in thyroid. The results demonstrate the superiority of the Hunter 

 method, both as to reliability of results and simplicity of manipulation. 

 Further evidence disproving the contention of Biggs that iodate is 

 formed during the fusion of thyroid by the Baumann process is pre- 

 sented. In practically all cases it was found that the older Baumann 

 method gives only 80 to 90 per cent of the amount of iodine obtained by 

 the Hunter method. The most probable cause of this difference is consid- 

 ered to be the loss of iodine which occurs during the acidification of the 

 aqueous solution of the fused residue, during which there is an active 

 evolution of C0 2 and since some of the nitrate of the fusion mixture is 

 always reduced to nitrite, there must also be present free iodine, which 

 is liberated by the nitrous acid generated from the nitrite upon acidi- 

 fication. This source of loss has been effectively overcome in the Hun- 

 ter method, by converting the inorganic iodine to the iodic state, and 

 at the same time removing the nitrite by means of sodium hypochlorite 

 solution, before the aqueous solution is acidified. Duplicate determin- 

 ations by the Hunter method are therefore quite satisfactory, while 

 in the case of the Baumann method frequent irregularities of results 

 which can only be explained on the assumption of a loss, are obtained. 



Since it has been claimed by Koch (Proc. Am. Pharm. Assoc, 55 : 

 371 . 1907), that the iodine content of desiccated sheep thyroids prepared 

 at different seasons of the year' was as much as three times as great in 

 the winter as in the summer months, an experiment was made for the 

 purpose of demonstrating the possible seasonal variation of the iodine 

 content of dog thyroids. The glands from groups of dogs killed at inter- 

 vals during more than a year at the Washington dog pound were analyzed 

 for their iodine, but no regular variation with season could be detected. 

 It appeared that the cause of this irregularity might be the individual 

 variation of the dogs, and analyses were therefore made of the dried 

 glands of individual dogs, with the result that very wide differences 

 (0.036 to 0.271 per cent iodine) were found. From these results it was 

 concluded that if there is a seasonal variation in the iodine content of 

 the thyroid of dogs, the individual variations under ordinary conditions 



