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IIICH-SCHOOL CHEMISTRY
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Laboratory Accidents ELBERT C. WEAVER Phillips Academy, Andover, Massachusetts
1. CONSIGN to the hall of unpleasant memories the exploding hydrogen generator. Just one exploded. This happened near the end of the run when the delivery tube came near a flame. Now it is the invariable rule of the laboratory that all hydrogen generators shall be taken apart after the gas is collected, before any flames are lighted. Pupils hum hydrogen from a jet regularly without danger of an explosion in the generator. A sample of the issuing gas is collected in an inverted test tuhe, and the tube is brought to a flame. If the jet can be lighted with the burning gas in the tube there is no danger. 2. Once a pupil raised his Bunsen burner by placing a textbook under it. When the potassium chlorate in the crucible above the burner spilled over onto the book, a meny fire resulted. The instructor, passing by a t the moment of the accident, sought to save the textbook ($2.00, less educational discount). Impulsively he placed his hand over the burning book. The flame was not smothered. The hand was badly burned. Hereafter they can burn the books. 3. Once after a mixture of potassium chlorate and manganese dioxide had been heated in a small hardglass test tube the mixture was standing on the lecture desk, cooling. Suddenly the tuhe burst. The closed
end described a trajectory in that void which exists between teacher and pupils in the classroom, striking the wall about 20 feet away with so little loss of elevation that its horizontal velocity must have been definitely dangerous. Apparently the mixture had fused across the tube. Hereafter, such mixtures cool under the lecture desk. 4. A demonstrator prepared a dishpan of soapsuds which were inflated with a mixture of acetylene and oxygen. By applying a lighted match, the desired detonation resulted. But the demonstrator emerged resembling a snowman, all visible portions covered with suds. He had neglected to attach a long extension to his match stick. 5. The ammonia fountain with the change in color effected by water treated with phenolphthalein indicator was a "must" for WI inexperienced demonstrator. He filled the flask well with ammonia gas, inserted a two-hole stopper equipped with a medicine dropper and a jet tube, supported the flask, and placed the lower end of the jet tube below the liquid. When the medicine dropper was pinched a loud noise resulted. A pale demonstrator stood holding a fragment of the medicine dropper between his fingers. The flask had vanished, blown to tiny bits. It was flat-bottomed.
