404? Prof. Graham on Phosphuretted Hydrogen, 



2. The self-accendible gas procured from phosphorus, water, 

 and lime, is always mixed with free hydrogen, varying in 

 quantity from 25 to 50 per cent., while the non-accendible 

 gas from phosphorous acid contains no hydrogen gas, but is 

 pure. Rose concludes, that the spontaneous inflammability 

 of the first species cannot depend upon this hydrogen, for 

 the other species is not made self-accendible by the addition 

 to it of any proportion of free hydrogen. On trying the ex- 

 periment, however, I obtained a different result. A quantity 

 of gas had lost its self-accendibility by standing over water 

 for two or three hours. To my surprise the addition to this 

 gas of hydrogen, in any proportion from one third of a volume 

 to three volumes, restored the self-accendibility of the gas. 

 Spontaneous inflammability was communicated likewise to the 

 gas procured from phosphorous acid, in some cases, merely 

 by adding hydrogen to it. It was perceived, however, early 

 in the course of the investigation, that hydrogen did not uni- 

 formly communicate the property in question, and that its 

 influence depended on something accidental, and not essential 

 to the gas. For instance, the hydrogen which comes over 

 almost pure, towards the end of the process for phosphuretted 

 hydrogen, itself had none of this property; nor did it appear 

 in hydrogen obtained from the following sources : From the 

 electric decomposition of water ; from the decomposition of 

 steam by iron; from the action of water on amalgam of potas- 

 sium ; or from the action of the following acids on zinc, namely, 

 muriatic, arsenic, and phosphoric. Even in the case of the ac- 

 tion of sulphuric acid on zinc or iron, which had first afforded 

 hydrogen possessing the property in question, it turned out 

 that only the hydrogen evolved at an early period of the ac- 

 tion is efficient, while the gas evolved after the vivacity of 

 the action is impaired, is nearly, and sometimes entirely, desti- 

 tute of any influence. The activity of the hydrogen was, in 

 short, traced to a slight impregnation of nitrous acid vapour 

 which it possessed. The sulphuric acid of commerce always 

 contains a small portion of some acid of nitrogen, probably 

 the hyponitrous, from which I find it cannot be freed by boil- 

 ing or concentration, continued for any length of time. On 

 quickly mixing sulphuric acid with two or three volumes of 

 water, the presence of nitrous acid is attested by its peculiar 

 odour, and almost certainly by the appearance of brown 

 fumes. 



That the hydrogen did not owe the property in question to 

 a trace of nitric oxide, which, combining with oxygen, might 

 by a slight consequent evolution of heat have an effect in 

 kindling the phosphuretted hydrogen, was proved by the fact 

 that the property in question could not be imparted to hydro- 

 gen by any proportion of nitric oxide : but to this point there 



