OXYGEN. 37 



acid. It may be likewise obtained in great quan- 

 tity from nitrat of potass (salt petre) in an earthen 

 retort exposed to a strong fire ; also from the red 

 oxide of lead, heated with or without sulphuric acid. 



Having procured a sufficient quantity of this 

 gas in separate vessels, its properties may be easily 

 examined. 



It will be found that water does not absorb it ; 

 for if some of it be agitated in a small vial half filled 

 with water, and again immersed into the trough, 

 it will not be diminished in quantity ; nor will the 

 water rise in an inverted vessel of this gas, if left 

 on the shelf of the trough for a day. 



Oxygen gas is eminently calculated to support 

 the combustion of bodies. Plunge a lighted taper 

 fixed to an iron wire, or a lighted splinter of wood, 

 and the combustion will proceed with a splendour 

 much encreased. 



The flame of a lamp urged by a stream of oxygen 

 gas, instead of common air, excites a heat more 

 intense than the hottest furnace. 



Even the metals which are not easily combustible 

 in common air burn in oxygen gas with great readi- 

 ness. Iron or steel wire burns in a very striking 

 manner. It should be kindled by having a small 

 bit of wood fastened to the point ; the combustion 

 of this will communicate to the steel wire, which 

 will continue to burn. The fused drops of iron 

 that fall down, when examined, will be found to be 

 no longer malleable, but brittle and converted into 

 the oxide of iron. The same change will take 

 place when the other metals are burnt in this gas. 



If a piece of charcoal, fixed to an iron wire, be 

 lighted by a blow pipe, and put into ajar of oxygen 

 gas, it will burn with a brilliant light, and throw 



D 3 



