Reactions in the system graphite-CrO 3-acetic acid II. Reactivity of the solution

Abstract

The intercalation of graphite from CrO 3-glacial acetic acid solution is effected only under the condition that certain amounts of Cr(VI) compounds are decomposing. This is the case as long as solid CrO 3 is dissolving and, additionally, at temperatures near the boiling point. Chromium trioxide does not intercalate itself, but an “intercalation-active chromium oxide” is formed in the solution. The oxidation state was identified as a Cr(V) compound by electron spin resonance. This substance, probably acetylchromate(V), is present in low concentration and reacts easily with graphite as well as with foreign substances. The “active chromium oxide” can be enriched in the solution by the application of an electrolytic current. In this way, the yield of intercalated substance is increased from 10% to more than 90%, referred to the added CrO 3. Investigations of the solution were carried out by u.v.-vis absorption spectrometry, by conductometry, and by electron spin resonance. In the intercalation compound the chromium probably exists in the oxidation state V. The formula C n +(CrO 3) − is suggested.