412 Prof. Graham on Phosphuretted Hydrogen. 



it explodes with a puff, like loose grains of gunpowder, and not 

 with the usual snap, the oxidation of the nitric oxide pre- 

 ceding by a sensible interval the oxidation of the phosphu- 

 retted hydrogen. Nitric oxide in a considerably smaller pro- 

 portion than g'jjth of a volume exhibits a sensible effect in re- 

 tarding the combustion of self-accendible gas, but does not al- 

 together prevent it. 



In the case of phosphuretted hydrogen which was not self- 

 accendible, small additions of nitric oxide, such as one to one 

 hundred, to five hundred, to one thousand, or to two thousand 

 volumes phosphuretted hydrogen, did not induce self-accen- 

 dibility when the nitric oxide employed had been previously 

 washed with caustic alkali. The experiment was tried with 

 three different specimens of washed nitric oxide. But nitric 

 oxide which had not been washed with alkali, particularly if 

 it resulted from a turbulent action of the nitric acid on cop- 

 per, and came over charged with red fumes, and was withal 

 newly collected, was pretty often efficient in making the gas 

 self-accendible. The proper proportion of such nitric oxide 

 for this purpose was found to be one volume to a quantity 

 between those of one thousand and two thousand volumes of 

 phosphuretted hydrogen. A greater or a less proportion of 

 the nitric oxide failed to produce the desired effect. All these 

 experiments with nitric oxide were made over water. 



It is well known that a mixture of phosphuretted hydrogen 

 and nitric oxide may be exploded by a bubble of oxygen gas, 

 a method of firing these gases first practised, I believe, by 

 Dr. Thomson. But Dr. Dalton found pure nitric oxide ca- 

 pable of oxygenating phosphuretted hydrogen in a gradual 

 manner when the two gases are left together, nitrous oxide 

 and nitrogen resulting. Possibly, therefore, it is by acting 

 itself upon phosphuretted hydrogen that nitric oxide pre- 

 vents atmospheric air from acting upon that gas in our expe- 

 riments. It is conceivable that the oxygenating action of ni- 

 tric oxide upon phosphuretted hydrogen may be promoted, 

 like that of air upon the same gas, by the presence of nitrous 

 acid, which will explain Dr. Thomsons experiment. 



The impregnating nitrous mixture of the foregoing experi- 

 ments was not destitute of nitric oxide ; but what proves that 

 the efficiency of the mixture did not depend upon the last-men- 

 tioned ingredient is the circumstance that the mixture lost 

 its virtue by standing over mercury for a week, during which 

 period the acid vapour was absorbed by the mercury, but the 

 nitric oxide remained, as appeared on admitting air to the 

 gaseous mixture. Hence we may conclude, that when nitric 

 oxide acts in producing inflammability in phosphuretted hy- 



