PRESIDENT S ADDRESS. Xlll 



hydrocarbon, ethane. The latter is a gaseous compound whose 

 structure is represented by the formida CH3-CH3 By the action 

 of bromine upon it Tve obtain bromethane, CHy-CH, -Br, a 

 pleasant smelling, volatile liquid. Acting on this Tvith a suitabk 

 metallic hydroxide should replace the bromine by an oxygen and 

 hydrogen atom and hence should yield alcohol if our constitutional 

 formula is correct. — 



CHo-CH.-Br - M0H=CH3-CH,-0H - MBr. 

 This result has been experimentally verified. 



In the c-onstitutional formula of alcohol just given, the assump- 

 tion is made that one atom of carbon can combine vrith another. 

 An extension of this assumption explains the remarkable com- 

 pound-forming capacity of carbon already mentioned^ By 

 supposing that one atom of carbon can combine with another, one 

 of these with a third, this in turn with a fourth, and so on, we 

 should obtain a structure analogous to a chain, of which carbon 

 atoms are the links. Xo other element seems to have any apjDreci- 

 able power of forming such atomic chains, and on the other hand 

 there appears to be practically no limit to the number of carbon 

 afoms that can enter into the carbon chain. Hence the multipli- 

 city and complexity of carbon compounds, and the variet}" and 

 difficulty of the problems presented by the synthesis of them. 



AVe owe the theory of valency to the labours of Frankland, 

 C'ouper, and Kekule. With its development, progress in the 

 formulation of the constitution of carljon compounds became 

 exceedingly rapid: and no less rapid was the advance of organic 

 synthesis, for the determination of the constitution of a compound 

 usually implied that either immediately, 01 at all events in no 

 long time, methods would be devised for the synthesis of it. In 

 this way. one by one. many of the organic compounds found in 

 Xature were artificially prepared. But numerous as these 

 preparations were they formed but a fmall fraction of the stream 

 of carbon compounds entirely new to the world which now began 

 to pour from chemical laboratories. The stream became a flood 

 when a few years later, Kekule, in a memoir regarded as the most 

 brilliant piece of reasoning in the literature of organic chemistry, 

 showed how the theon- of valency could be applied to explain the 



