CONSTITUTION OF AIR 



121 



continue to burn. The fumes which are formed are stopped by the asbestos 

 fibre. A quantity of red deposit is also found (this is really another form 

 of phosphorus), but may be got rid of by strongly heating it. 



When the apparatus is cool, disconnect the tube BA from the test-tube 

 and aspirator, and again weigh. It will be found that a decided increase 

 of mass has occurred. 



t t 



PHOSPHORUS ASBESTOS 

 FIBRE 



FIG. 93. Experiment to show that the fumes produced by burning phos- 

 phorus in a current of air are heavier than the phosphorus used. 



Different kinds of phosphorus. There are two kinds of phosphorus, 

 one called yellow phosphorus, and the other red, or amorphous, phos- 

 phorus. Yellow phosphorus catches on fire very easily ; the warmth 

 of the hand is quite enough to inflame it. For these reasons it is always 

 kept under water. It is generally bought in the form of sticks, which, 

 when freshly manufactured, are of a yellow waxy colour. This phos- 

 phorus can easily be cut with a knife, but the cutting should always 

 be done under water. However small the piece, it must never be 

 touched with the bare fingers but always lifted by small tongs or forceps. 

 If this precaution is not taken, the warmth of the fingers may cause 

 the phosphorus to catch on fire, and, as it is difficult to shake it off 

 when once alight, the burn which it causes is very severe and dreadfully 

 painful. In all experiments with yellow phosphorus these warnings 

 must be borne in mind. The red or powder form of phosphorus is 

 not so inflammable as the yellow kind, but it must be used with care. 



Phosphorus readily burns in the air. It is only necessary to touch 

 a piece of dry phosphorus with a hot wire to make it catch on fire and 

 burn. It burns with a dazzling bright flame, and at the same time 

 dense clouds of white fumes are formed, which spread throughout 

 the room. These facts are noticed until all the phosphorus has 

 disappeared. 



