48 EXPERIMENTS IN FA VOUR OF 



by the lamp ; one neck is connected with the porcelain 

 tube, as already stated, by means of an india-rubber 

 cork, and the other is bent down and inserted into a 

 vessel containing sulphuric acid. The central part of 

 the porcelain tube is heated by means of a furnace, 

 and when it has attained a vivid red heat the bulb is 

 joined on the end of the porcelain tube, which projects 

 from the furnace, being made thoroughly hot imme- 

 diately before the cork is inserted, the cork itself being 

 taken out of boiling water, and the neck of the bulb 

 being also heated with a spirit lamp before it is 

 inserted into the cork. A stream of air is now passed 

 through the apparatus by means of the gas holder, 

 and bubbles through the sulphuric acid at the other 

 end. The substance in the bulb is then boiled for ten 

 or fifteen minutes, the lamp withdrawn and the bulb 

 allowed to cool while the stream of air is still passing 

 through the porcelain tube, maintained during the 

 whole time at a vivid red heat. When the bulb is 

 quite cool the necks are sealed by means of a 

 lamp. The advantage gained by means of this 

 apparatus is that there is only one joint the perfec- 

 tion of which in any degree affects the success of the 

 experiment, and of that joint it is easy to make sure. 

 The porcelain tube also, being for a considerable part 

 of its length fitted with small fragments of porcelain, 

 all heated up to redness, easily insures that every 

 particle of air admitted to the bulb shall be thoroughly 

 heated" 



