132 



Domestic Science 



found to burst into flame, and to burn with greater 

 brilliancy than was the case when it was burning in 

 air. The partial extinction and re-ignition of the splint 

 may be effected several times in fact, as long as there 

 remains any powder at the end of the strongly heated 

 tube. When all the powder has disappeared, dis- 

 continue the heating, and examine the walls of the tube 

 just above the portion which has been heated. A thin 

 silvery metallic deposit is to be seen, which, on being 

 rubbed with the end of the splint, collects into small 

 globules easily recognised as quicksilver or mercury. 



Fig. 38. 



In this case, two effects of the action of heat have 

 been shown. The first was the change of colour, the 

 second the disappearance of the original substance and 

 the simultaneous appearance of two new bodies, the 

 gas which re-ignited the glowing splint and the mercury 

 left in the tube. The former change resembled those 

 previously observed regarding the action of heat upon 

 bodies, in that the body was not completely altered 

 by the change, but could be readily recognised as the 

 same substance after the withdrawal of the disturbing 

 effect of the heat. Such changes are distinguished as 



