30 G. H. KNIBBS. 



Let us briefly glance at a few of the greater facts of chemical 

 science, facts revealed to the world almost wholly in the century 

 just closing. Its origin is shrouded in as much mystery as 

 one of the most interesting personalities connected with its 

 early development, viz., Abu Musa Dschabir (Geber) [died about 

 776 A.D.?]. It is questionable, however, whether the term 

 4 chemistry' ought in strictness, to be applied to that body of 

 knowledge concerning metallurgy, tanning, and dyeing, possessed 

 by the ancients even long before Geber's time, since the facts were 

 unassociated ; that is to say, they were disconnected items of 

 knowledge. The alchemists, who flourished between the eleventh 

 and fifteenth centuries, and who made a considerable number of 

 chemical observations, proposed what was to some extent a really 

 general problem, viz., the transmutation of metals into gold, not 

 even now a wholly ridiculous conception ; for the idea of a protyle 

 is by no means excluded by the data of observation. But the 

 attack on the problem was unsystematic. Paracelsus [1493- 

 1541], on the other hand, boldly declared pharmacology to be the 

 legitimate aim of chemistry. These facts are interesting as shew- 

 ing the range and character of the early conceptions of the science. 

 The then prevailing theory of the threefold constitution of matter 

 was attacked in 1661 by the sceptical Boyle [1626-1692], an 



P V=kO 

 which expresses Boyle and Mariotte's and Charles' laws, provided we 

 reckon $ from the ' absolute zero.' In order to make this equation agree 

 more exactly with the volume changes of gases of different density sub- 

 jected to pressure, Van der Waals proposed in 1872 the modification 



the a term denoting an attraction coefficient andi> the sum of the volumes 

 of the molecules, or amount by which the space V in which they moved 

 was actually diminished by their own dimensions. Unfortunately Van 

 der Waals' equation does not wholly meet the difficulty. A fair idea of 

 the problem to be solved may be had by reading say, Tait's ' foundations 

 of the kinetic theory of gases/ and Burbury's criticism thereon, the latter 

 points out that Tait's system of elastic -spheres cannot discharge all the 

 functions of gaseous molecules, especially when the explanation of spectro- 

 scopic phenomena has to be made out. 



