Goocli and Perkins — Determination of Free Iodine. 33 



Art. VI. — The Gravimetric Determination of Free Iodine 

 by the Action of Metallic Silver; by F. A. Gooch and 

 Claude C. Perkins. 



[Contributions from the Kent Chemical Laboratory of Yale University — cc] 



AYhen in analytical operations it becomes desirable to deter- 

 mine free iodine in the presence of iodine combined in an 

 iodide, it is usual to have recourse to volumetric procedure 

 involving the preparation of standard sodium thiosulphate, for 

 use in neutral or acid solution, or of standard arsenite, for use 

 in solutions made alkaline bj a bicarbonate. 



Fig. 1. 



The present paper is an account of an endeavor to utilize 

 the well-known affinity between silver and iodine as the basis 

 of a gravimetric method for the determination of iodine in 

 general, and, incidentally, for the gravimetric standardization 

 of iodine solutions to be used in volumetric analysis. 



Inasmuch as the facility with which combinations may 

 take place between substances varies Avith their physical con- 

 ditions, several preparations of silver were tried with a view 

 to finding the form of silver best adapted to the purpose of 

 taking up iodine in analysis. The iodine was used in N/10 

 solution prepared in the usual way (12*7 gms. of iodine to 18 

 gms. of potassium iodide in one liter) and standardized against 

 arsenious acid. 



Am. Jour. Sci.— Fourth Series, Vol. XXVIII, No. 163. 

 3 



-July, 1909. 



