PAPERS OX CHEMISTRY AND PHYSICS 327 



The boiling with acid neutralized the alkaline salts 

 present but evidently did not remove all the impurities, 

 and neutral buffer salts may still have been present. 



A sample of ^'Xorit" purified charcoal was then tried 

 in the same way. This gave a very similar curve to the 

 commercial grade that had been treated with acid, ex- 

 cept that the curve was slig?itly lower This sample 

 was also found to contain considerable ash and was quite 

 impure. (Curve II). 



A cample of "Xorit" purified charcoal was then tried 

 found to give about the same results as the previous 

 commercial charcoal; however, when tried with oxalic 

 acid instead of rising gradually after neutralization, as 

 with the HCl, upon adding the alkali the first 5 cc. gave 

 a sudden rise^ then the curve is held to almost a hori- 

 zontal line which could only be raised slightly by an 

 excess of alkali. A large quantity of alkaline material 

 was sho^vll to be present since so little alkali was neces- 

 sary for neutralization. (Curve Y). 



On the other hand, the failure of the hydroxyl ions to 

 show up may be due to the presence of neutral buffer 

 salts. This curve is also shown on Plate III, Curve V. 



Samples of **Super-Filchar", both Pharmaceutical 

 and Sugar grades, were tried with results similar to 

 those of the other purified charcoals with the exception 

 of their being slightly acid in their reactions. 



Both samples contained considerable ash, showing 

 them to contain salts of some kind. 



Acids stronger than the X/20 were then tried with 

 the different charcoals. Here it was found that instead 

 of a gradual rise in the cui*ve as with the weaker acids, 

 the curve remained horizontal until near the neutral 

 point, then rose abruptly in a vertical line to nearly the 

 full concentration of the hydroxyl ion, similar to that 

 for the acid and alkali alone. 



This action is similar to that of other buffer solutions, 

 such as acetates, and phosphates which do not give a 

 buffer eft'ect with strong acids, and gives rise to the 

 theorv that the different reactions caused bv the various 



