Description of an Apparatus, &c. 277 



intense heat should be continued for some minutes to drive 

 off the last portions of- potassium which adhere to the turn- 

 ings with great obstinacy. 



Explanation of the Plate. 

 A The iron tube containing the potash. 

 B The stopper, ground air-tight. 

 C The central situation of the iron turnings. 

 D The furnace* 

 E The tube of safety. 

 F The pipe of the bellows. 



XLII. Description of an Apparatus for the Analysis of 

 the Compound Inflammable Gases by Slow Combustion ; 

 \uith Experiments on the Gas from Coal, explaining its 

 Application. By William Henry, M. D. Vice-Pres. 

 of the Lit. and PhiL Society, and Physician to the In- 

 firmary, at Manchester. Communicated by H. Davy, 

 Esq. Sec. R. 5.* 



JL he aeriform compounds of hydrogen and carbon, which 

 were already entitled to accurate investigation, as objects of 

 scientific research, have derived an additional claim to the 

 attention of the chemist, from their application to an import- 

 ant ceconomical purpose, described in a late communica- 

 tion to the Royal Society \. Yet there is, perhaps, no part 

 of chemistry, the investigation of which is beset with greater 

 difficulty, or with more numerous sources of error ; inso- 

 much, that the actual state of th*e science enables us to at- 

 tain scarcely more than approximations to the truth, and de- 

 grees of probability of greater or less amount. It was the 

 object of the experiments, which are described in the follow- 

 ing pages, rather to remove some of the obstacles, which 

 present themselves to a successful inquiry into the nature of 

 these bodies, than to acquire such facts, as may enable the 



* From Philosophical Transactions for 1808. Part II. 

 f See Mr. Murdoch's paper, p. 124.; and PhiL Mag. p, 113 — 119 of this 

 volume. 



3 3 chemical 



