395 How inflammable Air may be procured. [Book V. 



bent fo that it may be patted into a glafs vefiel full of 

 water inverted in the pneumatic apparatus. There 

 will then pafs into the glafs vefiel an aeriform fluid, 

 which is inflammable air or hydrogen gas. In this 

 ' procefs the water fuffvrs a decompofition, and while 

 the hydrogen pafles into the glafs receiver, the oxygen 

 unites with the fubftance of the gun barrel, and oxy- 

 dates or rufts its internal furf ice. 



By means of acids, however, inflammable air may 

 be obtained in greater abundance, and with more fa- 

 cility. When iron, zinc, or tin, are acted upon by 

 diluted vitriolic, or marine acid, confiderable quanti- 

 ties of this gas are extricated. In this cafe alfo the 

 water is decompofed, as is plain from the concen- 

 trated vitriolic acid not anfwering the fame ends as 

 the diluted, either in furnifhing the air or diflblving 

 the iron, &c. 



The apparatus for procuring this gas is the fame as 

 that which has been defcribed for producing fixed air, 

 only employing inftead of chalk, iron filings, fmall nails, 

 fmall pieces of iron wire, or grofsly powdered zinc. To 

 thefe materials fome oil of vitriol and water muft be 

 added, in the fame proportion as in the procefs for pro- 

 duping fixed air. 



The electric fpark, taken in any fpecies of oil, pro- 

 duces hydrogen or inflammable air, this fubftance being 

 a coniliiuent part of all the oils. The fame may be 

 iaid of ether, and alcohol or fpirits of wine, which con- 

 tain a great proportion of hydrogen. 



Mr. Cavallo informs us, that he has procured this 

 kind of air from the ponds about London, in the fol- 

 ing manner. Fill a wide--mouthed bottle with pond- 

 water, and keep it inverted in it; then with a ftick 

 ftir the mud at the bottom of the pond juft under the ' 



inverted 



