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On Phosphuretted Hydrogen. By Tuomas Granam, Esq, 
F. R. S. Ed., Lecturer on Chemistry in the Andersonian In- 
stitution, and V. P. Phil. Soc. Glasgow. 
(Read 1st December 1834.) 
Few substances have been made the subject of experimental 
inquiry more frequently than the compounds of phosphorus and 
hydrogen, and no subject is so remarkable for the various and 
conflicting results which it has presented to chemists of the 
greatest acuteness and practical skill. The obscurity which long 
hung over the subject has been dispelled, however, in a great 
measure, by the recent investigations of Henry Rose of Berlin. 
Although baffled in his early researches, that philosopher return- 
ed again and again to the subject, and at last succeeded in de- 
termining the chemical functions and true constitution of phos- 
phuretted hydrogen. He has shewn it to be analogous to am- 
monia in chemical character and composition. But hitherto two 
compounds of phosphorus and hydrogen had generally been ad- 
mitted to exist, which were believed to differ in composition, as 
they do in properties, one being spontaneously inflammable in 
atmospheric air, and the other not so. Rose establishes beyond 
all doubt that these gases are essentially of the same composition, 
and of the same specific gravity ; and, indeed, that they are mu- 
tually convertible, each into the other, without any addition or 
subtraction of matter that could be perceived. In explanation 
of their possessing different properties, under the same composi- 
tion, allusion is made by Rose to Jsomerism, or the doctrine that 
two bodies may exist identical in composition, but differing in 
properties. Certainly the existence of two gases, constituted 
