142 



CHEMISTRY. 



Fig. 68. 



German chemist who invented it. Coal 

 gas enters at , Fig. 58, and air enters at 

 #/ they mix in the tube before they issue 

 at c, and on applying a light at this orifice 

 we have a very clean hot flame. By stop- 

 ping up the hole, , with your fingers you 

 can cut off the supply of air, and conse- 

 quently of oxygen, and the flame will in- 

 stantly change its appearance, burning 

 with the usual partially smoky yellow 

 light of ordinary coal gas. Removing 

 your fingers, oxygen enters, a perfect com- 

 bustion of the carbon particles takes place, and the flame is 

 colorless again. 



In all chemical laboratories where gas is to be had, these 

 burners, and stoves constructed on the same principle, are 

 in constant use, being clean, cheap, and needing no attention. 

 After a Bunsen burner has been long in use it sometimes 

 burns badly, the gas igniting at the base of the tube, c, and 

 burning within it with an illuminating flame. This is be- 

 cause there is too much air in proportion to the gas, and by 

 cleaning the little hole in the jet at the base of the tube, <?, 

 more gas may be admitted and the evil reme- 

 died. 



182. Blowpipe. The oxidizing and deoxidiz- 

 ing flames referred to in 174 are obtained with 

 greater distinctness by using the little instru- 

 ment called a blow-pipe. This consists of a short 

 tube, generally of metal, either curved at one end 

 or made of two pieces, one fitting into the other 

 at right angles. By applying to a flame the 

 end which terminates in a jet with a very small 

 hole, and then blowing through the other end 

 with the mouth, the flame is materially altered 



