8 Mr. D alt on on Phosphuretted Hydrogen. [Jan. 



1 . There is but one combination of phosphorus and hydrogen, 

 as far as can be deduced from experiments hitherto made ; all 

 the varieties of phosphuretted hydrogen have arisen from the 

 circumstance that free hydrogen is liable to be produced less or 

 more in all the processes used for the generation of phosphu- 

 retted hydrogen. 



2. Phosphuretted hydrogen may be obtained in great purity 

 from phosphuret of lime by the method recommended by Dr. 

 Thomson (Annals of Philosophy, vol. viii. p. 89), provided the 

 phosphuret has been well secluded from the atmosphere ; but if it 

 has been previously exposed for a few hours to the atmosphere, 

 the gas will be much more copious, and contain from 50 to 80 

 per cent., less or more, of free hydrogen, and only the rest 

 phosphuretted hydrogen. 



3. Pure phosphuretted hydrogen may easily be withdrawn 

 frern hydrogen by liquid oxymuriate of lime ; it absorbs the 

 former gas, and converts it into phosphoric acid and water, 

 almost as readily as green sulphate of iron absorbs nitrous gas ; 

 and the latter or free hydrogen is left unaffected. 



4. Pure phosphuretted hydrogen may be mixed with safety in 

 narrow tubes (-fe of an inch diameter) with pure oxygen ; and in 

 due time the mixture may be transferred into any sort of vessel 

 without explosion, and kept many hours without any sensible 

 chemical action. An electric spark fires it instantly, with a 

 violent explosion and a brilliancy surpassing that of any other 

 gas. Prudence requires that very small portions of the mixture 

 should be exploded ; with a strong tube having the glass -i- of an 

 inch thick, I do not think it safe to explode more than 15 water 

 grain measures of phosphuretted hydrogen at once. 



5. One volume of phosphuretted hydrogen requires, as nearly 

 as I have ascertained, two volumes of oxygen for its complete 

 combustion. Phosphoric acid and water are formed. 



6. Pure phosphuretted hydrogen, by being electrified for one 

 or two hours in due quantity, expands nearly 4- of its original 

 volume. Phosphorus is deposited, and the residual gas is 

 hydrogen mixed with less or more of phosphuretted hydrogen 

 which may have escaped decomposition, and which is deter- 

 minable by exploding with oxygen. If any atmospheric air be 

 present (which is almost unavoidable in the small quantity of 

 five or six per cent.), at first electricity perceptibly diminishes 

 the gas ; but it soon begins to expand, though in that case it 

 can scarcely be made to exceed 25 per cent, on the first volume. 



7. Water freed from air absorbs fully ± of its volume of this 

 gas. This was first announced by Sir H. Davy, of what he 

 calls hydrophosphoric gas, which appears from this and other 

 properties to have been nearly pure phosphuretted hydrogen. 

 The gas, I find, is capable of being expelled again by ebullition, 

 or by agitation with any other gas in the usual way, but not 

 without a loss of less or more phosphorus. 



