PAPERS OX CHEMISTRY AXD PHYSICS 325 



acid. Even the addition of a large excess of the acid 

 brings the Ph. value down to slightly below the nentral 

 point. 



The experiment was then repeated, nsing oxalic acid 

 instead of the hydrochloric, with practically the same re- 

 sults. 



These cnrves are quite different from that of Bovie, 

 as his curve is affected on both sides of the nentral point. 

 That is, his curve is lowered much below the noimal 

 cni*ve before reaching the nentral point, while the curve 

 for this charcoal is only affected on the acid side of the 

 line. 



13- 

 IZ- 

 11- 



lo- 

 g- 

 s' 



7- 

 6- 

 5- 

 4- 

 3- 

 1- 



C Z .^_^<i 



Plate I. 



If adsorption is the cause of the effect, there is here 

 no evidence of the adsorption of the hydroxyl ions. On 

 the other hand the results could have been due to the 

 presence of alkaline buffer salts in the charcoal. 



These titrations were then reversed, starting with the 

 acid, taking the voltage of Ph. reading, then adding the 

 charcoal and completing the titration with the alkali. 

 On adding the charcoal to the acid a sudden rise in the 

 Ph. reading was noted, the concentration of the hydro- 

 gen ions being reduced nearly to the neutral point. 



That alkaline reactions are responsible is indicated 

 by the fact that neutralization was complete at about 10 

 cc. while in the noi*mal curve 25cc. were required. If 



