Chromosulphuric acid

Glass apparatus which appears to be particularly dirty or greasy is cleaned by soaking in chromosulphuric acid (concentrated sulphuric acid containing about 100 g of potassium dichromate per litre), followed by a liberal washing with tap water, and then with distilled water. 

Procedure Fill two-thirds of a test-tube with chromosulphuric acid (concentrated), and set aside overnight. Next day empty the test-tube, rinse cautiously with running cold water, then with distilled water. Into this test-tube pour 2 ml silver nitrate (0- 1m) and 2 ml distilled water. Then add dilute ammonia (2m) dropwise, mixing the solution vigorously by shaking, until the last traces of the silver oxide precipitate disappear. Then add 2 ml saturated hydrazine sulphate solution and shake the mixture vigorously. The silver mirror forms within a few seconds. The solution should be discarded after the test (cf. 

Chromic acid (25 %). Pour 25 ml chromosulphuric acid cautiously, under constant stirring, into 70 ml water. After cooling dilute the solution with water to 100 ml. 

Crude montan wax (a mixture of esters of straight-chain saturated C26-C34 carboxylic acids) is a by-product of lignite and separated from lignite by an extraction process. Oxidative bleaching of black crude montan wax with hot chromosulphuric acid produces off-white, industrial montan wax acids. Esters of mono- and polyfunctional short-chain alcohols, esters of long-chain natural or synthetic fatty alcohols as well as complex esters are synthesized starting from montan wax acid [155]. 

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