SOME OBSERVATIONS ON E. C. KENDALL'S METHOD 



OF ESTIMATING IODINE IN THYROID 



PREPARATIONS. 



S. B. KUZIRIAN. 



In presenting- this short note on Kendall 's method of estimat- 

 ing- iodine in thyroid preparations, it is perhaps desirable to give 

 a short review of the method. For the details of manipulation 

 of the metliod the wi*iter recommends a careful study of the orig- 

 i3ial paper.^"- 



The procedure is essentially to oxidize the organic matter by 

 fusion with sodium hydroxide with the aid of small quantities of 

 potassium nitrate in a nickel crucible. The "iused mass is dis- 

 solved in hot water, one c.c. of a ten per cent solution of sodium 

 bisulphite and a few drops of methyl orange are added. It is 

 acidified with 85 per cent sirupy phosphoric acid. The hydro- 

 iodic acid produced is oxidized to iodic acid by addition of a few 

 drops of liquid bromine. The whole mass is placed on a hot 

 plate and with the aid of talc powder is boiled to remove excess 

 of bromine. Ten to fifteen drops of a solution of sodium sali- 

 cylate are added to take up any 'bromine that mig'ht have escaped 

 expulsion, the mixture is then cooled, after which five c.c. of a 

 ten per cent solution of potassium iodide and three to five c.c. of 

 sirupy phosphoric acid are added and the iodine liberated is ti- 

 trated with 0.02 N. sodium thio-sulphate. 



While Kendall's modified method was used by the author oi 

 this paper for analysis of a large number of feeds and samples 

 of ewes' milk for their iodine content, some difficulties were met 

 with on account of interference of ash and added bromine. 

 Forbes, Beegle, and others, seem to have encountered the same 

 difficulties, as shown in their bulletin. ^ 



Satisfactory results were o'btained, however, when the follow- 

 ing details were carefully observed : 



1. In destroying organic matter, it is advantageous to use 

 more sodium hydroxide and less potassium nitrate to obviate the 

 formation of large quantities of nitrite, which tends to liberate 

 iodine. 



IE. C. Kendall, Jour. Biol. Oliem., 19, pp. 251-254, 1914. 

 'E. C. Kendall, Jour. Amer. Chem. Soc, 34, 894, 1912. 

 ^Forbes, Beegle, and others, Bui. 299, Ohio Agr. Exp. Sta., Wooster, O. 



