Conductivity of Hypophosphoric Acid Solutions. 109 



this evidence is of little value. Unfortunately the degree 

 of acidity recommended and used by Rosenheim and 

 Pinsker for this process is in doubt, as their statements 

 are somewhat ambiguous, but in these two blank experi- 

 ments the hydrochloric acid appears to have been about 

 N/4 (certainly not below N/8). That such a degree of 

 acidity (or even one a good deal lower), would produce 

 a very considerable hydrolysis under the conditions 

 named by Rosenheim and Pinsker is at once evident from 

 the reaction velocity observed in Experiment 6 above, if 

 due allowance be made for the difference in temperature. 

 This is confirmed by the experiment recorded in Table 

 III, in which the composition of the reaction mixture was 



Table III. 





Hydrolysis of Hypophosphoric Acid. 







Temper 



ature 



87°-95°. 



Iodine 



and 



thiosulphate 



solutions approximately N/50. 







Iodine 





Na.SA Per cent of 



Time 





solution 





solution hypophosphate 



heated 





added 





required hydrolyzed 



min. 





cm 3 





cm 3 









5000 





44-63 



60 





5000 





41-07 10 



90 





5000 





39-54 14-5 



120 





5000 





38-39 17-3 



oo 





5000 





(9-52)* 



* Calculated from standards of solutions used. 



the same as in Experiment 6, but the bath in which the 

 sealed tubes were immersed had an initial temperature 

 of 87°, which rose steadily to about 95° during the course 

 of the experiment. Although the concentration of the 

 hydrochloric acid was only about N/4, seventeen per cent 

 of the hypophosphoric acid had been hydrolyzed at the 

 end of two hours. 



The Molecular Formula of Hypophosphoric Acid. — 

 Though the weight of evidence favors the view that the 

 molecular formula of hypophosphoric acid is H 4 P 2 6 

 rather than H 2 PO : „ the question is still under debate, 

 Rosenheim and co-workers 6 supporting the simpler 

 formula. The fact, established by our reaction velocity 

 measurements, that the hydrolysis is a monomolecular 



"Rosenheim, Stadler and Jacobsohn, Ber. chem. Ges., 39, 2S37, 1906; 

 Rosenheim and Pritze, ibid., 41, 2708, 1908 ; Rosenheim and Pinsker, ibid., 

 43, 2003, 1910. 



