COMPOUNDS OF HYDROGEN. 



51 



pared by boiling together hydrate of lime, water, and phosphorus ; 

 the water is decomposed, and hypophosphite of Hme and phosphu- 

 retted hydrogen are formed, thus : — 



Water J Hydrogen 

 ^^*^' i Oxygen 



2 Phosphorus. 

 Lime 



^ Phosphuretted 

 I Hydrogen 



^ Hypophosph 

 rous acid, 



°-( 



Fig. 19. 



-^ K Hypophosphite 

 f of lime. 



The most remarkable feature of this gas is its spontaneous inflam- 

 mability ; so that if the beak of the retort in which it is evolved be 

 placed under water, as each bubble of gas rises through the liquid 

 it takes fire, and forms a beautiful ring of a dense white smoke, 

 which enlarges as it ascends. 



Compomids of Carbon and Hydrogen. — The number of these 

 compounds has now become very great ; but most of them belong 

 properly to the domain of organic chemistry ; two of them, how- 

 ever, are generally considered under the head of inorganic che- 

 mistry : these are Light carburetted hydrogen and Olefiant gas. 



Light carburetted hydrogen^ 77iarsh gas, fire-damj), dicarburet 

 of hydrogen, CH^ ; — is formed in stagnant pools by the decomposition 

 of vegetable matters ; and may be procured by stirring up the mud 

 at the bottom of the pool, and collecting the gas. It may be pre- 

 pared by strongly heating -a mixture of acetate of soda, hydrate of 

 potash and quicklime : the gas is derived from the de- 

 composition of the acetic acid of water. 



Frop. — Colourless, tasteless, nearly inodorous ; a 

 non-supporter of combustion or respiration, but very 

 combustible, burning with a bright yellow flame ; — mixed 

 with oxygen in due proportions, it forms an explosive 

 mixture ; products of its explosion or combustion, water 

 and carbonic acid ; sp. gr. '559. This gas is fre- 

 quently evolved in large quantities from coal mines, 

 and explodes on contact with the flame of the miner's 

 lamp, causing the most disastrous consequences. 

 Sir H. Davy's safety-lamp) was invented to obviate 

 these fatal results. It consists of a common oil-lamp, 

 enclosed in a cage of wire-gauze, made double at the 

 upper part, containing about 400 apertures to the 

 square inch. When this lamp is taken into an ex- 

 plosive mixture, although the fire-damp, passing inside 

 the gauze, may burn within the cage with such energy 

 as to heat the. metallic tissue to redness, the flame is 

 not communicated to the mixture on the outside, in 

 consequence of the cooling effect produced upon the 

 heated gas by the wire-gauze ; most fortunately, the 



