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CORRESPONDENCE
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because of their acid-forming characteristics. They reprecipitate from solution because of their base-forming characteristics. Such compounds are appropriately called amphoteric. Yours res~ecffullv.
INSERTING GLASS TUBING INTO TIGHT-FITTING RUBBER STOPPERS To the Editor DEARSIR: I t is my experience, and no doubt that of several others too, that a great many workers in the laboratory get occasional cuts on their hands through forcing a glass tubing into a tight-fitting mbher stopper. Similarly, a great difficulty is usually felt in taking out tight-fitting rubber stoppers from delicate pieces of apparatus to which they have stuck owing to long exposure. I have found the following method very simple and safe for removing these. Take an ordinary cork borer of the size next bigger to that of the tubing to be inserted and push it into the rubber stopper. While it is in position insert the glass tubing and, holding th6 latter in the desired position, pull out the cork borer slowly. The stopper no* grips the tubing firmly and there is no looseness in the fit. If it is desired to remove the tubing, the cork borer is first gently but firmly inserted and the tubing drawn out quite easily. The method appears very simple, but works admirably. I hope the publication of this letter in your JOURNAL may help many a worker engaged in chemical laboratories. Yours faithfully, V. N. PATWARDHAN OF SCIENCE INDIANINSTITUTE HERBAL,BANGALORE, INDIA
