Glass stopper, holding

The propyne is passed directly from the tank or lecture bottle to a cold-finger condenser filled with a slush of Isopropyl alcohol and dry ice. The condenser is attached to a 20n-mL, three-necked flask equipped with a gas-inlet adapter and a glass stopper. The flask has been previously calibrated to hold 85 mL of liquid. 

Never put a glass stopper from a liquid-reagent container down on the lab bench. Either hold the stopper or place it in a clean place (such as a clean beaker) while you dispense reagent. 

The top of the upright tube in the reaction flask is closed by a cork stopper holding a glass plunger which may be used for pushing back into the flask any sublimed 2-furancarboxylic acid. 

The apparatus consists of a reaction flask (A), a condenser-scrubber trap (B), a series of traps (C) and a micro weighing bottle (D). The reaction flask in A is a round-bottomed flask having a volume of approximately 13 ml fitted with a gas inlet tube in the form of a capillary tube extending to the bottom of the flask. The scrubber trap in B has a side arm with a ground glass stopper in the upper part and is capable of holding a maximum of about 4 ml of wash solution. 

Place a drop of the test solution (or a grain of the solid test sample) in the tube of Fig. 11.53 and coat the knob of the glass stopper with a thin layer of the zinc nitroprusside paste. Add a drop of 2m hydrochloric or sulphuric acid and close the apparatus. After the sulphur dioxide has been evolved, hold the stopper for a short time in ammonia vapour. The paste is coloured more or less deep red. 

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