( J75 ) 



From which 



50 + 0.87 

 Vh = -—^- X 200 = 11690 



Ch- 

 and 



0.00006 



-1+1 



3306 



0.87 



50 4- 1.56 



^56 



X 100 = 3306 



+ 1 



1 



0.00006 X 11690 



- 11690 X 0.00004749 



= 0.00004749 



=: 0.0000089. 



Ka = 0.00006 . 



11690 1 — 3306 X 0.00004749 



The electrolytic process gave 0.0000096. ') 



Determination of the dissociation constant of propionic acid. 

 Given: /^^ == 0.00006 vu=z 442.5 



2;^, --=1020 

 Indicator: methjiorange acid. 

 Found : 



15 cc of indicator were diluted with 25 cc of water 

 was restored on adding 1.5 cc solution of benzoic acid. 



the colour 



n=- 



25 



1.5 



1.5 



X 442.5 == 7816 



15cc of indicator were diluted with 10 cc of water 

 w^as restored on adding 6 cc solution of propionic acid. 



10 + 6 

 V/, = — ^- X 1020 = 2720 



the colour 



6 



Cn 

 and 



0.00006 



- 1 + 



2720 1 

 0.00006 X ^XT^ X 



+ 1 



0.00006 X7816 

 7816 X 00006261 



= 0.00006261 



0.0000128 '). 



7816 1—2720X0 00006261 



Found by the electrolytic process: 0.0000134. 



This method may, perhaps, prove useful in cases where the 

 electrolytic method meets with difficulties, for instance in the deter- 

 mination of very small concentrations of hydrogen-ions or in the 

 determination of the concentration of hydrogen-ions in presence of 

 other cathions. I intend making further experiments in that directiou. 



Laboratory, Netherland Technical ScJi.ool. 

 Enschede, 15 May 1905. 



1) OsTWALD. Zeitschr. fur Physik. Chemie 1889, p. 261. 

 3) OsTWALD. Zeitschr. fur Physik. Chemie 1889. 



