ldn Van Name and Huf- — Estimation of 



hypophosphate solution is plainly evident, though the 

 results are in other respects very concordant with one 

 another. As the sample of acid sodium hypophospliale 

 from which the solution was prepared had heen recrystal- 

 lized but once, it seems reasonable to conclude that the 

 reduction of iodine was due to the presence of a little 

 phosphite 10 in the hypophosphate, and not to oxidation 

 of the hypophosphate itself. 



This conclusion is supported by the following experi- 

 ments: Salzer, 17 in 1886, stated that normal sodium 

 hypophosphate, Na 4 P 2 G , is partly oxidized by iodine, 

 though neither hypophosphoric acid nor the acid sodium 

 hypophosphate are attacked. To test this point a solu- 

 tion prepared from a sample of the salt which had been 

 recrystallized three times was treated with sodium 

 hydroxide (free from carbonate) in quantity slightly 

 greater than that calculated to be necessary to form the 

 normal sodium salt. Two portions of this solution were 

 each treated with a measured quantity of standard 

 iodine more than sufficient to completely oxidize all the 

 hypophosphate. After two hours' standing in the dark 

 both of these solutions were colorless, but upon acidify- 

 ing and titrating, the iodine found was practically equal 

 to that taken, the deficiencies being only 0.04 cm 3 and 

 0.08 cm 3 of the iodine solution, respectively, though the 

 hypophosphate present had a reducing power sufficient 

 to call for about 50 cm 3 of iodine. Losses as small as 

 these might easily be due to experimental error, or to 

 slight impurities in the reagents used, and certainly do 

 not show that the hypophosphate has been attacked. It 

 seems probable, therefore, that Salzer mistook the dis- 

 appearance of iodine caused by iodide and iodate forma- 

 tion, which necessarily takes place in the rather strongly 

 alkaline solution of the normal sodium hypophosphate, 

 for an actual oxidation of the latter. 



It is evident, in any case, that under the conditions 

 recommended above for the determination of phosphor- 

 ous acid, no appreciable oxidation of the hypophosphate 

 is to be feared. We have used the method for many 

 analyses in the course of a study of the hydrolysis of 

 hypophosphoric acid, 18 and have found it entirely satis- 

 factory. 



10 This impurity is always present in the crude hypophosphate as first 

 prepared, and can only be eliminated by repeated crystallization. 

 "Ann. Chem., 232, 116, 1886. 

 18 See the following article. 



