Kanematsu Sugiura and K. George Falk 19 



continually be broken up with a stirring rod. The end point is not 

 considered to have been reached until after all tlie material is in 

 Solution. One cc. of m/25 thiosulfate sol. is equivalent to 0.00508 

 gm. of iodine, or 0.0014 g^i. of hexamethylenetetramine. Two re- 

 sults of iodine determination by this method may be given : 



0.1013 gm. of substance required 15.73 cc. of OT/25 thiosulfate sol., equiva- 

 lent to 0.0799 gm- of I, or 78.9 percent of I. 



0.1044 gm- of substance required 16.16 cc. of w/25 thiosulfate sol., equiva- 

 lent to 0.0820 gm. of I, or 78.6 percent. of I. 



Mean iodine content: 78.7 percent. 



The diiodine Compound may be prepared by adding the requisite 

 amount of iodine dissolved in alcohol to hexamethylenetetramine 

 dissolved in water (Horton), or by extracting the tetraiodine Com- 

 pound with ether eight or nine times in a separatory funnel, with 

 shaking. In this way a dark greenish yellow diiodine Compound 

 was obtained, whichgavethe following analytic results for nitrogen: 



0.2020 gm. : 0.02787 gm. of N, or 13.80 percent of N 

 0.2016 gm. : 0.02798 gm. " " 13.88 percent of N 

 Mean: 13.84 percent of N; calc. for (CHo)eN4L, 14.23 percent. 



The diiodine Compound is much less soluble than the tetraiodine 

 product, being almost insoluble in the ordinary common organic 

 solvents. 



Method of estimating hexamethylenetetramine. The 

 method, based upon the properties of the tetraiodide, is conducted 

 as follows. 



To the Solution in question, 50 cc. being a convenient amount to 

 use, containing no proteins or similar substance precipitable by 

 iodine, there is added from a buret or pipet with stirring, an alco- 

 holic iodine sol. containing 3.6 gm. of iodine in 100 cc. of 95 percent 

 ethyl alcohol. If hexamethylenetetramine is absent, no precipitate 

 is foi-med at first but after further addition, bluish black iodine pre- 

 cipitates. On the other hand, if hexamethylenetetramine is present, 

 a precipitate is formed, which is first brownish yellow in color; finally, 

 reddish to dark brown. About 20 percent excess of iodine is ad- 

 visable; if more is added, iodine may be precipitated. The amount 

 needed may be judged by the formation of the precipitate as the 

 iodine sol. is added, or the mixture is filtered and treated with more 



