Prof. Graham on Phosphnretted Hydrogen. 405 



will be occasion to recur. At an earlier stage in the inquiry, 

 some experiments were made upon the effect of other gases 

 than hydrogen upon phosphuretted hydrogen. None, with the 

 exception of sulphuretted hydrogen, (evolved by the action of 

 sulphuric acid on sulphuret of iron, and which, therefore, con- 

 tains free hydrogen,) appeared to favour the accendibility of 

 the gas. On the contrary, the addition of all others, and even 

 of hydrogen and sulphuretted hydrogen themselves above a 

 certain proportion, distinctly impeded or destroyed the ac- 

 cendibility of this gas. Thus, one volume phosphuretted 

 hydrogen ceased to be inflammable when mixed with the fol- 

 lowing proportions of different gases : 

 With 5 volumes hydrogen. 



2 — — — carbonic acid. 



S nitrogen. 



1 volume olefiant gas. 



„* — * — & — 

 sulphuretted hydrogen. 



T 1 ^ nitric oxide. 



^i_ muriatic acid. 



£ ammoniacal gas. 



It is to be remarked, however, in reference to the preceding 

 table, that some specimens of phosphuretted hydrogen appear 

 to be more highly accendible than others, and that there is 

 considerable latitude in the proportion of foreign gas which 

 may be requisite for destroying the spontaneous inflamma- 

 bility of a given specimen. Often a much smaller portion 

 suffices than is stated in the table. I have found half a vo- 

 lume of carbonic acid or nitrogen to have the effect in certain 

 cases. Of course the introduction of any trace of air with the 

 gases must be carefully guarded against. Nitrous acid, when 

 present in hydrogen in too small a proportion to enable that 

 gas to communicate spontaneous inflammability to phosphu- 

 retted hydrogen, or to be perceived by the smell, may be de- 

 tected by the effect of the hydrogen upon a prepared mixture 

 of non-accendible phosphuretted hydrogen and air, which 

 mixture may be had transparent and quite free from white 

 smoke. The addition of hydrogen to this mixture occasions 

 the immediate appearance of a dense white smoke, the oxida- 

 tion of the phosphorus being partially induced if an infini- 

 tesimal proportion even of nitrous acid exist in the hydrogen. 

 Although the oxidation of the phosphorus takes place at the 

 expense of the air present, and only when air is present, yet 

 the nitrous acid appears to be speedily consumed ; the fumes 

 soon ceasing, but appearing again on every subsequent addi- 

 tion of active hydrogen, till several volumes have been added, 

 or till the oxygen of the air present is exhausted. 



That the influence of the hydrogen was referrible to the ni- 



