Page:Popular Science Monthly Volume 89.djvu/330

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��Popular Science Monthly

��An Alarm Bell for Chemists

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��[N chemical laboratories , where various hquids are treated by slow processes, the receiving bot- tles often overflow, thereby wasting material and incur- ring a risk of dam- .ige, if the liquid is of a destructive nature. An attach- ment for bottles that will cause an alarm bell to ring can be installed cheaply.

The device consists of an electric contact made to close by the pressure of a float which rises in a tube as the level of the liquid nears the top of the bottle. A long tube, thrust through a rubber cork into the solution, contains a drawn- glass tip, from the ends of which plati- num wires protude. At the upper ends they are connected to batteries and a bell. At the lower end they are bent into any desired shape, so that the circuit is closed when the float rises.

The float consists of a sealed-off glass tube containing a drop of mercury to prevent it from being too buoyant. The float can be tipped with metal, so than an electrical connection is formed between the wires when the tip touches them; or it may consist merely of the sealed-ofY tube, which, in rising, presses the wires together. The lower end of the tube containing the float is curved inwards, so that the float will not drop out when the device is removed.

Getting Iron Scraps Out of Deep Holes

APIECE of iron or steel can be removed from a small, narrow hole with the use of a hor.seshoc magnet and a nail. The nail is magnetized its full length and thus attracts the piece of iron or steel which can then be very easi- ly removed.

����Rope and a Lever as a Pipe Wrench

SOMETIMES in ""* '"* ' tightening or loosening pipes and pipe fittings, a suit- able wrei.ch may not be at hand. This difficulty is easily overcome by using a piece of rope and a lever which may be a bar of iron, or a piece of pipe or wood.

The method of using this de\-ice is shown in the accompanying illustration. The rope is doubled and gi\en a few turns about the pipe (enough to insure a grip), the lever A is then inserted in the loop of the rope at B, and a strain is put on the end C to prevent the rope's slip- ping. The more turns of rope about the pipe, the less strain is required at C. The pipe is turned by the lever A the same as by any pipe-wrench used by steam-fitters. — William Philip.

A Safety-Holder for Hatpins

THE loss of an expensive hat- \)m may be preven- ted in the following manner. Cut 4 ins. from the point of an old hatpin; and bend it into a ring, allowing the point to overlap the blunt end about 3^ in. Bend the point slightly to one side so it can catch on to the hat. Solder the ring on to the back of the head of the hatpin. When the pin is inserted in the hat, it is slightly turned to enable the cur\ed point to grip the material of the hat, thus preventing its being lost. — Thomas Sheehan.

Taking the Yellow out of Rubber

OFTEN experimenters find that hard rubber is affected by the sun, which gives it a yellowish color. A good remedy is to rub the rubber with dr\- pumice until the owtler turns yellow and then to polish with carbon disulpiiide which can l)e bought at any drugstore. This gives it a beautiful black finish.

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