n 



Van Name and llujf — Estimation of 



Table I. 



Standardisation of "Phosphorous Acid Solution, Oxidation by Permanganate. 

 Kiihling 's Method Modified. 



Sodium Thiosulphate Solution, 1008 N/10. 



H 3 PO ; 



KMnO, 



Na,S 2 : . 







solution 



solution 



solution 



H,PO„ 



H;,P0 3 



taken 



taken 



required 



found 



found 



cm 3 



cm 3 



cm 3 



grm. 



grm./cm 3 



000 



5000 



47-22 







1000 



5000 



38-50 



003607 



0-003607 



1500 



5000 



34-20 



005385 



0003590 



2000 



5000 



29-82 



007197 



0003599 



2500 



5000 



25-57 



008954 



0003582 



7200 



15000 



7915 



0-2585 



0003591 



standard of the solution. It should be noted that hypo- 

 phosphates, though they are readily oxidized by hot 

 permanganate, can not be estimated by this method. 

 Low and irregular values are obtained, probably because 

 of the insolubility of zinc hypophosphate under the 

 conditions. 



lodometric Estimation of Phosphorous Acid in the 

 Presence of Potassium Bicarbonate. — In Table II are the 







Table II. 







Estimation of Phosphorous Acid — Method of Sieverts. 



Iodine 



solution 1133 N/10. 



Arsenite solution 09812 



N/10. 







Iodine 



Arsenite 





Per cent 



H,PO„ 



solution 



solution 



H 3 PO, 



of 



taken 



taken 



required 



found 



theory 



cm 3 



grm. 



cm 3 



grm. 



grm. 





500 



001795 



2500 



24-39 



0-01804 



100-50 



1000 



003591 



24-50 



19-31 



003617 



100-72 



15-00 



005387 



45-07 



38-58 



005420 



100-61 



2000 



007182 



44-32 



3318 



0-07247 



100-91 



2000 



0-07182 



28-35 



14-80 



007219 



100-52 



3000 



0-1077 



4803 



28-52 



01085 



100-74 



5000 



01795 



4805 



10-77 



01800 



100-28 



results of a series of determinations obtained by the 

 method of Sieverts, 10 already referred to. Measured 

 volumes of the standard phosphorous acid solution were 

 placed in glass-stoppered flasks, to each of which was 

 added two grams of potassium bicarbonate and a known 

 excess of standard iodine solution. The flasks were then 



10 Zs. anorg. Chem., 64, 29, 1909. 



