7 6 PRACTICAL ORGANIC CHEMISTRY allow subsequent escape of air. Place 5 ml. of water in the flask and then add 3-3 ml. (6-1 g.) of concentrated sulphuric acid slowly with shaking: finally add 3-5 g. of coarsely crushed sodium dichromate and some fragments of unglazed porcelain. The dichromate rapidly dissolves in the acid, which has become hot dur-" ing the preliminary dilution. Place in the dropping-funnel a mixture of 1-5 ml. (1-2 g.) of ethanol and 6 ml. of water, and allow it to fall slowly drop by drop down the condenser into the oxidation mixture. A vigorous reaction occurs and the mixture becomes green owing to the formation of chromic sulphate, Cr 2 (SOJ 3 . At frequent intervals* during the addition of the ethanol, mix the contents of the flask by vigorous shaking. When the addition is complete and the reaction has subsided, heat the flask on a boiling water-bath for 15 minutes. Then detach and reverse the condenser, and reconnect
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