The most widely used method is to measure the carbon’s capacity to adsorb carbon tetrachloride (referred to as CTC) and express this as a w/w %. This is determined by flowing CTC laden air through a sample of carbon of known weight, under standard conditions, until constant weight is achieved.
The apparatus essentially consists of a means to control the supply of air pressure, produce a specified concentration of CTC and control the flow rate of the air/CTC mixture through the sample.
The weight of CTC adsorbed is referred to as the carbon’s % CTC activity. However, this test does not necessarily provide an absolute or relative measure of the effectiveness of the carbon for other adsorbates or under different conditions. CTC activity is now universally accepted as a means of specifying the degree of activation or quality of activated carbon. Commercially available carbons range from 20% to 90% CTC activity.
