] 824.] On the Combination of Potassium and Oxygen. 205 



and the whole disappears. Thus it cannot be consumed com- 

 pletely by two different proportions of oxygen gas, which dis- 

 tinguishes it i'rom phosphuretted hydrogen gas. 



The effect produced by subliming sulphur in this gas shows 

 that it contains its own volume of hydrogen gas. Hence the 

 hydrogen in a volume of it will require for combustion half a 

 volume of oxygen gas. The remaining 0*75 volume of oxygen 

 gas must have combined with the phosphorus vapour, and con- 

 verted it into phosphoric acid. Now phosphorus vapour requires 

 for this its own volume of oxygen gas. Thus it is evident that 

 phosphuretted hydrogen gas when left standing over mercury 

 loses one-fourth of its phosphorus, and becomes a compound of 



Sp. gr. 



1 volume hydrogen gas 0*0625 



f volume phosphorus vapour 0-6250 



0-6875 



So that its specific gravity is reduced from 0-9027 to 0*6875, and 

 it contains just ten times as much phosphorus by weight as of 

 hydrogen. It is a compound of 4 atoms hydrogen and 3 atoms 

 phosphorus. 



M. Vauquelin will see from the above statement that the gas 

 in question is not the same as Davy's gas to which I gave the 

 name of bihydroguret of phosphorus (a harsh term, but expres- 

 sive of the composition of the gas). We may call it, for the 

 sake of distinction, subphosphuretted hydrogen gas. 



Thus phosphorus and hydrogen gas unite in at least three 



proportions; viz. 



Hydrogen. Phosphorus. 



1. Phosphuretted hydrogen composed of. . . 1 atom + 1 atom 



2. Subpliosphuretted hydrogen 4 +3 



3. Bihydroguret of phosphorus 2 H- 1 



I am, Sec. Thomas Thomson. 



Article VIII. 



On an Anomaly presented by I he Combination of Potassium and 

 Oxygen; with some general Observations on Combination. By 

 the Rev. J. B. Emmett. 



(To the Editors of the Annals of Philosophy.) 



GENTLEMEN, Great Oiiseburn, Aug. 6, 182-1. 



In estimating the specific gravity of oxygen as it exists in 

 different solid compounds, potash presents a remarkable pheno- 



