Removing fixed stoppers

Removing Fixed Stoppers.—Hot water should be run on to the neck of the bottle and the stopper gently tapped with another glass stopper. The neck of the bottle may be inverted in hot water for a minute and afterwards gently tapped. If these methods fail, and if the contents of the bottle are not easily inflammable, the neck of the bottle may be rotated in a flame prior to tapping. Similar methods may be applied to fixed stop-cocks. 

Caution Excess pressure may be generated The rubber stopper must be held tightly and the pressure released by opening the stopcock once or twice. The tube is now fixed vertically to the stand with the stoppered end uppermost. The stopper is removed quickly and the gas mixture ignited with the flame of the gas burner. 

In a long memoir on the methods of separating metals (1752) Scheffer remarks that (hot) concentrated sulphuric acid will dissolve silver from its alloy with gold, but says this acid was then more expensive than aqua fortis. If fixed alkali (potassium carbonate) solution is added to a solution of silver in aqua fortis and the bottle at once stoppered, there is no precipitate but if the stopper is removed there is a brisk effervescence and a precipitate is formed. Pure silver is obtained by fusing precipitated silver chloride with fixed alkali and a little nitre. ... 

It is sometimes found that the stopper of the weighing bottle becomes fixed, so that the liquid is prevented from vaporizing, or vaporizes very slowly. To obviate this, the stopper should be loosened, or removed altogether (if the liquid, is not too volatile), before the weighing bottle is dropped on to the glass rod at D. In this case, care must be taken that the weighing bottle is not filled so full that the liquid wets the stopper and the bottle must be lowered carefully, but as... 

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