DARCO D A R C O D E P A R T M E N T · A T L A S POWDER C O M P A N Y Darco General Sales Offices—60 EAST 42nd STREET, NEW YORK 17, N . Y. ATLAS POWDER C O M P A N Y , C A N A D A , LTD., B R A N T F O R D , C A N A D A
A c t i v a t e d carbon is a n efficient reducing agent Primarily used as a means of removing impurities by physical adsorption, activated carbon also can act as a reducing agent. I t has a large surface area at which the reduction reaction can take place. Several specific types of applications have utilized this characteristic of carbon advantageously.
Carbon for dechlorination This dual use of activated carbon proves valuable in the reduction of traces of halogens in solution. Carbon reacts with chlorine to form the HC1 and COg. Excess chlorine introduced into water supplies, for example, can be readily removed by passing the water through a granular carbon filter. Filters of this
type have shown an effective life measured in years in treating water containing free chlorine in parts-per-million concentration. It should be noted that t h e grade of carbon selected for this application is designed for adsorption from liquids, rather than being a gas-adsorbent type. Its pore openings are large enough to admit large molecules . . . thus it can adsorb organic impurities a t the same time t h a t it performs the reduction. The carbon does not adsorb t h e chlorine gas, nor the chlorine odor. It changes the free chlorine to HC1 by chemical reaction. This action is basically different from t h e usual function of carbon in adsorbing large molecules (such as fatty acids) which cause odor.
Reduction of permanganates Similarly, residual quantities of permanganates added for oxidation in a solution can be removed by carbon. Potassium permanganate, for example. is reduced by carbon to the tetravalent „ form; the carbon is oxidized to carbonate. The characteristic deep color of the permanganate disappears . . . but not through any decolorizing action of the carbon. The removal of color is due t o the chemical reduction reaction that takes place.
Selection of grade of carbon Any carbon, of course, will provide the basis for a reducing reaction. Only an activated carbon, however, can serve a dual function . . . acting chemically t o effect reduction, and physically to adsorb other impurities of a colloidal, surface active or complex molecular nature that may be present. The use of Darco activated carbon in appropriate grades may prove valuable in applications that you are now facing. Write to us giving complete details, and we'll be glad t o make specific recommendations.
To safeguard the quality of Darco activated carbon, samples are taken from production and subjected to0laboratory tests. 'Each "day's ·production must meet rigid standards. Adsorptive capacity, the most important characteristic of a carbon, is measured against, a standard solution. Production samples of Darco must measure within 5% of required relative efficiency. Filterability, purity and pH of water extract are also checked. Special grades of Darco receive additional tests required for their particular application. Through constant vigilance, in the various stages of manufacturing and in laboratory checking, the uniformity of Darco is held at a consistently high level . . . to assure you that every shipment of Darco you receive, whether by the carton or the carload, will always perform the way you expect in your own process.
V O L U M E
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J A N U A R Y
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1955
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