Conductivity of Ilypophosjphorie Acid Solutions. 105 



mixture was prepared by mixing a solution of acid 

 sodium hypophosphate (approximately N/20 in reducing 

 power) with concentrated hydrochloric acid in definite 

 proportions by volume. This solution was kept at a 

 constant temperature in a thermostat, and from time to 

 time samples for analysis were taken with a pipette and 

 run into glass-stoppered flasks which contained the 

 requisite amount of disodium hydrogen phosphate, 

 together with enough sodium hydroxide to exactly neu- 

 tralize the hydrochloric acid present. Each sample was 

 then treated with the same amount of iodine solution 

 (an excess), and after standing was finally acidified and 

 titrated with thiosulphate. 2 



To obtain the final titration (for the completed reac- 

 tion) a sample was run from the pipette into a stout 





Table II. 







Bate of Hydrolysis of Hypopliosphoric Acid at 60° 





Hypophosphate solution 



approx. N/! 



10 H 2 Na,P 2 0„. 





5. Reaction mixture: 



One vol. 









HC1 of sp. grav. 



1-185 made 



6. One 



vol. of 1062 



normal HC1 



up to -1 vols, with hypophos- 



and 



three vols, of hyporihos- 



phate sol. 





phate sol. 





Elapsed Thiosul- 





Elapsed 



Thiosul- 





time phate 



K 



time 



phate 



K 



min. em 3 





min. 



cm 3 





44-63 









46-48 





36-75 37-51 



000630 



1434 



42-75 



0-0000783 



65-50 32-95 



000632 



3603 



3801 



00000766 



93-92 2906 



000640 



6485 



32-73 



00000766 



122-8 2619 



000624 



9359 



28-43 



00000772 



152-3 23-45 



000626 



13697 



23-82 



00000759 



184-5 20-70 



000643 



16577 



21-49 



00000751 



222-6 18-67 



000629 



19445 



19-58 



00000749 



284-3 1611 



000620 



QO 



11-41* 





» 10-20 











* Calculated from standards of solutions used. 



glass-stoppered bottle, the stopper clamped in place, and 

 the bottle immersed in boiling water for eight hours, 

 after which the sodium hydroxide and phosphate were 

 added and the analysis completed as before. 



Owing to the long duration of some of the experiments, 

 and the consequent possibility of error from gradual 

 change in standard of the thiosulphate or iodine solu- 

 tions, the samples were usually not titrated when taken, 

 but set aside after the neutralization until the series was 



2 For details of the procedure, see the preceding article. 



