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XLVIII. Note on the Atomic Volume of Solid Substances. By 

 James Dewar, F.R.S.E., Chemical Demonstrator in the Uni- 

 versity, Lecturer on Chemistry , Veterinary College, Edinburgh*. 

 THE investigation of the volume retained by different elemen- 

 tary substances, when combined in the solid condition, has 

 attracted the attention of many chemists. We have only to look 

 at the laborious memoirs of Schroter, Kopp, Playfair and Joule, 

 Boullay, Filhol, and others, to be convinced of the great amount 

 of labour expended on the subject. Nor is it at all remarkable 

 that so many workers should take to this field of research, 

 when we remember the simplicity of the laws regulating the 

 combining volumes of gaseous substances, and the probable 

 extension of some such similar law to the solid condition of 

 matter. Emboldened by analogy, the forementioned workers 

 endeavoured to find some constant to which volumes of ele- 

 ments and compounds held the relation of some simple multi- 

 ple, and thus extend the apparent simplicity of Prout's law of 

 combining weights to combining volumes. The great object hi 

 view was evidently to extend the speculations and laws of l)alton 

 and Gay-Lussac to the volumes of solid substances, and thus to 

 arrive at some general explanation of the results. However 

 creditable the desire to reveal simplicity out of the apparent 

 chaos, no one, in examining the subject, can help arriving 

 at the conclusion that the means employed to extract the seem- 

 ing harmony from the results were purely arbitrary. It does 

 not follow, however, that the results were fruitless, although no 

 .great generalization was discovered. The solid state of matter 

 is relatively far more complicated than either the liquid or 

 gaseous condition. The uniformity of expansion of gaseous 

 matter, and the easy comparison of liquid substances under 

 similar conditions, enable us to arrive at some satisfactory con- 

 clusions regarding the volume in these states : but in examin- 

 ing solid matter, we have no guarantee that the substances are 

 under similar physical conditions ; we cannot, therefore, ex- 

 pect the same uniformity in the results. But although, strictly 

 speaking, we may entertain grave doubt on the real value of the 

 results, yet in some cases we cannot help recognizing some 

 curious analogies, especially on comparing similar classes of 

 compounds. It is not the object of this note either to criticise 

 or discuss the labours and speculations of others, no originality 

 being claimed in the subject matter itself, all that is original 

 being merely the addition of a few new analogies. 



The first important discovery in the subject of atomic volumes 

 was made by Schroter. He observed that the equivalent volume 

 of oxygen, obtained by subtracting the volume of metal in the 



* From the Proceedings of the Royal Society of Edinburgh, Session 

 1869-70. Communicated bv the Author. 



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