140 Domestic Science 



when in the tube. Heat the water in the larger beaker 

 to boiling. Bubbles of air will escape through the 

 coloured liquid as the water becomes hot. After the 

 water has boiled for half a minute, remove the beaker 

 and let the bulb cool down, leaving the open end ,of 

 the tube under the surface of the alcohol. As the tube 

 cools, some of the coloured liquid will be seen to travel 

 along the tube into the bulb. When this action appears 

 to have ceased, replace the beaker containing the warm 

 water, and again heat it to boiling-point. It will be 

 found that the alcohol in the bulb rapidly boils away, 

 leaving the bulb and tube apparently empty. Again 

 remove the hot water, and allow the apparatus to cool. 

 As before, the alcohol will be driven into the bulb and 

 this time the bulb will be found to become almost 

 entirely filled with the coloured liquid. By repeating 

 the heating and cooling, it is possible to expel 

 all but the smallest trace of air from the bulb 

 and tube. Let the bulb and tube cool down 

 at this stage till it no longer appears warm 

 to the hand, leaving the open end of the 

 tube under the alcohol as before. We will 

 suppose that it is desired to show on the 

 finished thermometer the ordinary tempera- 

 tures experienced in this country. To this 

 end, surround the bulb with water at a tem- 

 perature of about 40, as registered by a 

 Centigrade thermometer. Stir the water well, 

 and after leaving the bulb in the warm water 

 for a minute, seal off the upper end of the 

 thermometer by applying a small blowpipe Fl 42 - 

 flame to the end just beyond the tapering part. (Instead 

 of a blowpipe flame, the flame obtained by unscrewing 

 the barrel of a Bunsen burner, and lighting the gas at 



