Conductivity of Ilypuphosphoric Acid Solutions. 115 



by conductivity measurements, but we have not attempted 

 to do this. 



Table VI shows the molecular conductivities of H 4 P 2 6 









Table VI. 













Results of Other Investigators. 







V 



31-6 



63-2 



126-4 252-8 505-6 1111-2 



2222-4 



Eosenheim 



p- 



367-4 



3990 



443-4 491-4 549-8 608-8 ' 



739-2 



and Pinsker 



1* 



420-4 



496-8 



522-1 581-1 646-2 716-6 





Parravano 



V 



32 



64 



128 256 512 1024 





and Marini 



as measured by Rosenheim and Pinsker at 25-6°, and the 

 results of Parravano and Marini for 25°. Our results 

 lie between the two series but nearer to those of Rosen- 

 heim and Pinsker. The high values obtained by Parra- 

 vano and Marini are probably due to failure to free their 

 lead salt from adhering impurities, or to oxidation of the 

 hydrogen sulphide. The discrepancy between our values 

 and those of Rosenheim and Pinsker is hard to explain. 

 It is unlikely that our solutions contained any consider- 

 able amount of impurities other than the products of 

 hydrolysis. This conclusion is supported both by the 

 qualitative tests above mentioned, and by the approxi- 

 mate agreement between the observed conductivities of 

 the two solutions, prepared independently, and by some- 

 what different methods. Finally, the comparative purity 

 of our solutions is shown by the fact that their molecular 

 conductivities after complete hydrolysis, referred to the 

 formula H 2 P0 3 , coincide very closely with the mean of 

 the molecular conductivities of phosphorous and phos- 

 phoric acids, as will be evident on comparing our results 

 with the following figures for these acids at 25°, as given 

 bv Kohlrausch and Holborn: 10 









Table VIJ. 











Molecular Conductivities at 25°. 









V 



= 16 



32 64 128 



256 



512 



H3P03 



M 



= 222 



257 292 318 



337 



351 



H,P0 4 



P- 



= 124 



156 195 240 



279 



317 



Mean 



i* 



= 173 



206-5 243-5 279 



308 



334 



It therefore seems probable that the results of Rosen- 

 heim and Pinsker are somewhat too low. 



10 Leitvermogen der Electrolyte, p. 167, from measurements by Ostwald. 

 These values for phosphoric acid are in good agreement with the more 

 recent results of Noyes and Eastman, Carnegie Inst. Pub. No. 63, p. 262, 

 1907. For phosphorous acid Ostwald 's values seem to be the only ones 

 which have been published. 



