Studies in surface chemistry of carbon blacks Part II. Surface acidity in relation to chemisorbed oxygen

✍ Scribed by Balwant Rai Puri; R.C Bansal

• Publisher: Elsevier Science
• Year: 1964
• Tongue: English
• Weight: 685 KB
• Volume: 1
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(64)90007-7

✦ Synopsis

Surface acidity of a series of samples of carbon blacks was determined by titrating with sodium hydroxide and barium hydroxide, and the value in each case was found to be almost exactly equivalent to the amount of carbon dioxide evolved. The acidity decreased on evacuation at gradually increasing temperatures, and the decrease at a particular temperature was equivalent to the amount of carbon dioxide eliminated at that temperature.

These observations cannot be explained on the basis of carboxylic or lactone groups. It appears more likely that the acidity is due to the existence of an adsorbed layer of carbon dioxide held chemically or quasichemically on the surface giving rise to what may be termed a "CO,-complex".

The strength of the complex as an acid depends upon its concentration per unit surface. Treatment of carbon blacks with hydrogen at 170" was found to cause an appreciable increase in their acidity, probably due to the reduction of quinones to hydroquinones.