316 



Popular Science Monthly 



An Alarm Bell for Chemists 



r 



[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, whicli 

 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. 



