523 



his mathematical pursuits must be the wish of every friend of 

 science. 



Dr. Andrews, 



1 have the honour of presenting to you one of the Royal Medals, 

 which has been adjudged to you for your valuable paper on the 

 Thermal Changes accompanying Basic Substitutions'^. I hope this 

 will not be the last on chemical subjects that we shall receive at 

 your hands. 



Since our last Anniversary we have lost many distinguished mem- 

 bers of our Society, of whom the usual obituary will contain a short 

 account ; among these we have to regret the death of Sir Henry 

 Halford, who for so long a period presided over the College of Phy- 

 sicians ; and of Dr. Hope, who for very many years was Professor of 

 Chemistry in the University of Edinburgh. We have still more 

 immediate reason to lament the decease of one of our ablest and 

 most zealous colleagues, — of that distinguished astronomer the late 

 Mr. Baily, who has always taken an active share in the business 

 as well as in the scientific pursuits of the Royal Society. We have 

 also to deplore the death, at a venerable age, of Dr. Dalton of Man- 

 chester, whose eminent discoveries have so largely contributed to 



* The Royal Medal in Chemistry is awarded to Dr. Andrews of Belfast, 

 a chemical investigator of acknowledged ability and accuracy. He may be 

 said to have first opened the subject of the Heat evolved in Chemical Com- 

 binations, by a valuable paper published three years ago in the Transactions 

 of the Royal Irish Academy, which was followed by a second, and attracted 

 to the inquiry the attention of the French Academy, who lately proposed 

 it as the subject of the great Monthyon prize, with special reference to the 

 experiments of Dr. Andrews contained in these papers. 



One of the most important general results of the former papers was, that 

 the heat on uniting a particular base or metallic oxide with an acid is con- 

 stant, although the acid be varied. This result was brought out by using 

 dilute solutions, and is certainly established in a considerable number of 

 acids within that degree of accuracy which thermal experiments appear to 

 admit of. 



In such neutralizations of an acid by a base, it is well known that what 

 really happens is not the simple and direct combination of the acid and 

 base, but the displacement of the basic water of the acid by a more power- 

 ful base. Hence Dr. Andrews is led, in the paper in our Transactions 

 which is rewarded by the Medal, to inquire, whether, in the displacement of 

 other bases than water, such as lime, oxide of copper, &c., the same law 

 holds. He employed potash as the displacing base, and found that the 

 sulphate, nitrate, acetate and chloride of copper, when decomposed by that 

 base, all evolve the same heat ; or that the heat is determined by the base, 

 and not by the acid. The experiments are very numerous, embracing the 

 principal magnesian oxides, also soda, ammonia and peroxide of iron ; and 

 the results accord with the general conclusion. 



This extension or generalization of his former law is possessed of much 

 chemical interest, and is the first great step in a line of inquiry of which 

 the further pursuit is greatly to be desired, from the light which it may be 

 expected to throw upon the fundamental laws of chemical combination. 



