324 ILLINOIS STATE ACADEMY OF SCIENCE 



a similar buffer action. The results show that the ap- 

 parent buffer effect produced by animal charcoal is prob- 

 ably caused by chemical action of the alkali or acid added 

 upon the adsorbed gases and salts contained as impuri- 

 ties in the charcoal, rather than by any true adsorption 

 by the charcoal itself. Obviously most animal charcoal 

 contains small quantities of impurities such as phos- 

 phates, carbonates, tartrates and oxalates together with 

 some salts of calcium, sodium, or potassium and also 

 adsorbed gases such as carbon dioxide and hydrogen sul- 

 fide. 



To test their effects, titrations were made with the 

 various grades of commercial charcoal obtainable, and 

 with charcoal made from pure cane sugar and containing 

 no mineral salts. The results obtained in these titrations 

 are plotted as curves on which the conclusions are based. 



The titrations were made with a simple titration ap- 

 paratus devised in the laboratory and similar to one de- 

 scribed in Central Scientific Co. Bulletin No. 86. This 

 method of titrations is especially suited for the purpose, 

 because it indicates the actual hydrogen ion concentra- 

 tion at all times and also gives the neutralization point. 

 Furthermore, the charcoal suspensions are so black that 

 indicator changes could not be clearly marked. 



EXPERIMENTS 



The first experiment was made with a sample of com- 

 mercial animal charcoal bought on the market, the titra- 

 tion being made with N/20 sodium hydroxide and N/20 

 HCl. Curve I, Plate I, represents the normal curve for 

 this alkali and acid. 



A second titration was then made by first running in 

 25cc. of the alkali, then adding one gram of the charcoal. 

 No change was observed in the voltage or Ph. reading 

 upon the addition of the charcoal, but as the titration was 

 carried out the curve (curve II) follows the normal until 

 near the neutral point; then instead of showing an 

 abrupt drop it is straightened out, indicating the elimina- 

 tion of the hydrogen ions of the acid by adsorption or by 

 the action of some substance which interacts with the 



