1824.] Scientific Notices— Chemistry. 147 



2. Note on a Contradiction in Thomson's System of Chemistry 

 respecting Phosphuretted Hydrogen Gas. By M. Vauquelin * 



At p. 273 of Thomson's System of Chemistry, article " Phos- 

 phuretted Hydrogen," we read as follows : " When electric 

 sparks are parsed through this gas for some time, the phospho- 

 rus is deposited, and pure hydrogen gas remains. But the 

 volume of the gas is not altered by this process. Hence it 

 follows, that phosphuretted hydrogen gas consists of hydrogen 

 gas, holding a quantity of phosphorus in solution. This quan- 

 tity is discovered by subtracting the specific gravity of hydro- 

 gen gas from that of phosphuretted hydrogen." Further on, p. 

 275, it is said that bihydroguret of phosphorus (proto-phosphu- 

 retted hydrogen) " may be procured by exposing phosphuretted 

 hydrogen to the direct rays of the sun. A quantity of phospho- 

 rus is deposited, and the gas is changed into bihydroguret of 

 phosphorus." 



" When sulphur is sublimed in this gas," continues Dr. 

 Thomson, " the volume is doubled, and two volumes of sulphur- 

 etted hydrogen gas are formed. When potassium is heated in 

 it, the volume is also doubled. Hence it is obvious that it 

 (proto-phosphuretted hydrogen gas) is a compound of two 

 volumes of hydrogen gas, united with the same quantity of 

 phosphorus that exists in a volume of phosphuretted hydrogen 

 gas, and condensed into one volume." 



Here is a manifest contradiction : in fact, if phosphuretted 

 hydrogen gas (perposphuretted hydrogen) be a solution of phos- 

 phorus in the hydrogen without condensation, and if this gas be 

 converted by the luminous rays, or by electricity, into proto- 

 phosphuretted hydrogen, without any change of volume, it is 

 evident that the latter is also a solution of phosphorus in hydro- 

 seen without condensation, and that the only difference between 

 the two gases consists in the quantity of phosphorus. 



If the second part of Dr. Thomson's reasoning be true, the 

 phosphuretted hydrogen gas must be reduced to half its volume 

 by being converted into protophosphuretted hydrogen ; but, 

 according to Thomson bimself, that is not the case. It would 

 probably be the first instance in which hydrogen has been found 

 to be condensed, on abandoning a solid which it had held in 

 solution : the contrary more frequently occurs. 



It was important, however, to ascertain if the volume of pro- 

 tophosphuretted hydrogen gas be doubled by heating sulphur in 

 it ; for, as it is proved by accurate experiments, that sulphuretted 

 hydrogen contains an equal volume of hydrogen, if the volume 

 of protophosphuret be actually doubled by the process, it must 

 contain two volumes of hydrogen condensed into one. 



* From the Annalcsde Chimie. 



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