20 Compounds of Hexamethylenetetramine 



iodine sol., or an approximate determination is made first and then 

 a more accurate one with new Solution. After all the iodine has 

 been added (as a rule, 5-8 cc. are required), the mixture is allowed 

 to stand about 10 min., with occasional stirring, and filtered with 

 suction through a Gooch crucible containing an asbestos mat (filtra- 

 tion through paper is unsatisfactory). Re-filtration through the 

 same mat is advisable. The precipitate is washed five to ten times 

 with cold water. The precipitate and crucible may be dried in a 

 vacuum desiccator over calcium chloride to constant weight (no 

 appreciable loss of iodine occurs at room-temperature within reason- 

 able time-limits), and weighed as tetraiodine Compound. Better 

 than weighing the precipitate is the titration of the iodine present 

 with thiosulfate sol. For this purpose, the precipitate and crucible 

 are transferred to a beaker, 50 cc. of water and 3 cc. of glacial 

 acetic acid added, and the mixture titrated with w/25 sodium thio- 

 sulfate sol., with added starch sol. as described above. 



If the liquid, in which hexamethylenetetramine is to be deter- 

 mined, contains protein matter (such as albumin in urine, etc), an 

 equal volume of methyl alcohol is first added, the mixture allowed 

 to stand 1-2 hr. at room-temperature, filtered by decantation through 

 folded filter paper, evaporated to one-third the volume in a current 

 of air or under diminished pressure, iodine sol. added, and the de- 

 termination carried out as already described. The presence of glu- 

 cose does not interfere with the estimation of hexamethylenetet- 

 ramine. 



The results of the analyses of the tetraiodine preparations given 

 before, in the description of the substance, show that, as precipi- 

 tated directly, the product is practically pure. Test analyses with 

 different mixtures showed, however, that errors may be introduced 

 by incomplete precipitation of the hexamethylenetetramine, as well 

 as by iodine that may be carried down with the precipitate. A few 

 of these results are given below : 



Two samples of 0.0502 gm. each of hexamethylenetetramine in 

 50 cc. of water, precipitated with 6 cc. of iodine sol., filtered, etc., 

 required 40.02 and 41.01 cc. respectively of 0.0388 in thiosulfate 

 sol., corresponding to 0.0543 gm. and 0.0557 S^^'^-> respectively, of 

 hexamethylenetetramine. 



