Organic 2 Review Problem 103

Organic 2 Review Problem 103 - P REPARATIONS 87 Then...

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PREPARATIONS 87 Then collect 5-6 gas-jars filled with the acetylene, and carry out the following tests. (1) Odour. The gas collected in this way has a somewhat onion-like odour, which is much less pronounced than that of the crude gas given off directly from the carbide without subsequent purification. Absolutely pure acetylene, however, is almost odourless. (2) Bromine. Slip the glass cover of a jar momentarily aside, add 2-3 ml. of bromine water, replace the cover and shake the contents of the jar vigorously. Note that the bromine is absorbed only very slowly, in marked contrast to the rapid absorption by ethylene. This slow reaction with bromine water is also in marked contrast to the action of chlorine water, which unites with acetylene with explosive violence. (Therefore do not attempt this test with chlorine or chlorine water.) (3) Alkaline Permanganate. To another jar add similarly 2-3 ml. of very dilute potassium permanganate solution con- taining sodium carbonate. On shaking the jar the permanganate
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