METHODS AND MANIPULATION 41 to the amount of the compound available. The bottle or tube should at once be labelled, so that the identity of the compound, its melting-point, and any particular details concerning the method of purification employed, are clearly recorded. The label should also record the "tare" (i.e., the weight) of the empty bottle or tube, including that of the stopper or cork, so that the total weight of material available can subsequently be determined without removing the substance from the bottle. Stable liquids of high boiling-point can be similarly stored in stoppered bottles or in corked specimen tubes: in the latter case, however, unless the liquid is required again shortly, it is advisable to wax the cork in order to hold it firmly in position and also to prevent the liquid from slowly seeping through the cork itself. For this purpose, the cork should be placed firmly in position, and the inverted tube dipped into some clean paraffin wax which has been heated
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