TRANSACTIONS OF SECTION B. 659 



Section B.— CHEMICAL SCIENCE. 



President of the Section — 

 Professor Sir H. E. Eoscoe, Ph.D., LL.D., F.R.S., F.C.S. 



THURSDAY, AUGUST 28. 



The President delivered the following Address : — 



With the death of Berzelius in 1848 ended a well-marked epoch in the history of 

 •our science ; with that of Dumas — and, alas ! that of Wurtz also — in 1884 closes a 

 second. It may not perhaps he unprofitable on the present occasion to glance at 

 some few points in the general progress which chemistry has made during this 

 period, and thus to contrast the position of the science in the' sturm und drang' 

 year of 1848, with that in the present, perhaps, quieter period. 



The differences between what may properly he termed the Berzelian era and 

 that with which the name of Dumas will for ever he associated show themselves 

 in many ways, but in none more markedly than by the distinct views entertained 

 as to the nature of a chemical compound. 



According to the older notions, the properties of compounds are essentially 

 governed by the qualitative nature of their constituent atoms, which were supposed 

 to be so arranged as to form a binary system. Under the new ideas, on the other 

 hand, it is mainly the number and arrangement of the atoms within the molecule, 

 which regulate the characteristics of the compound, which is to he looked on not 

 as built up of two constituent groups of atoms, but as forming one group. 



Amongst those who successfully worked to secure this important change of view 

 on a fundamental question of chemical theory, the name of Dumas himself must 

 first be mentioned, and, following upon him, the great chemical twin-brethren 

 Laurent and Gerhardt, who, using both the arguments of test-tube and of pen in 

 opposition to the prevailing views, gradually succeeded, though scarcely during the 

 lifetime of the first, in convincing cbemists that the condition of things could 

 hardly be a healthy one when chemistry was truly defined ' as the science of bodies 

 which do not exist.' For Berzelius, adhering to his preconceived notions, had been 

 forced by the pressure of new discovery into the adoption of formulae which gra- 

 dually became more and more complicated, and led to more and more doubtful 

 hypotheses, until his followers at last could barely succeed in building up the 

 original radical from its numerous supposed component parts. Such a state of 

 Things naturally brought about its own cure, and the unitary formulae of Gerhardt 

 began to be generally adopted. 



It was not, however, merely as an expression of the nature of the single chemi- 

 cal compound that this change was beneflcial, but, more particularly, because it laid 

 open the general analogies of similarly constituted compounds, and placed fact as 

 the touchstone by which the constitution of these allied bodies should be ascer- 

 tained. Indeed, Gerhardt, in 1852, gave evidence of the truth of this in his 

 well-known theory of types, according to which, organic compounds of ascer- 

 tained constitution can he arranged under the four types of hydrogen, hydrochloric 

 acid, water, and ammonia, and of which it is, perhaps, not too much to say that 

 it has, more than any other of its time, contributed to the clearer understanding of 

 the relations existing amoiiL"t chemical compounds. 



Another striking difference of view between the chemistry of the Berzelian era 

 and that of what we sometimes term the modern epoch is illustrated by the so- 



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