732 Proceedings of the Royal Irish Academy. 



that distinguished chemist effected the reduction of his metal in a 

 different manner. 



If we admit with Awdejew, and with Dehray, the numher 4-6 to 

 be the equivalent of glucinum (H =1), the question remains whether 

 the " atomic weight," so called, is a multiple of the equivalent by 

 2 or 3. 



If, as some assert, the " atomic weight " is 4*6 x 3 = 13-8, the only 

 known oxide of glucinum must resemble alumina. If, on the other 

 hand, the atomic weight is 4*6 x 2 = 9'2, glucina must be an oxide like 

 that of zinc or of magnesium. Each view has received the support of a 

 group of chemists of the highest eminence, but owing to peculiar difficul- 

 ties surrounding the case, an appeal to chemical criteria has hitherto 

 been insufficient to decide between the two conflicting opinions — a deter- 

 mination of the specific heat of the metal, or of the vapour density of one 

 of its compounds of simple constitution, being necessary for the final 

 settlement of the question. Of these methods I chose the former, and, 

 having made several determinations of the capacity for heat of metallic 

 glucinum, I have the gratification to state that the data obtained 

 lead to the conclusion that the atomic weight of glucinum is double 

 the equivalent weight. Glucinum is, therefore, a diatomic metal with 

 an atomic weight of 9*2 ; though, I may add, this number may be 

 slightly affected by a new determination of the equivalent in which 

 I am engaged. 



The method pursued in making the necessary determinations upon 

 which to found the conclusion just stated was devised for the pur- 

 pose of this inquiry ; and as it is essentially different from any with 

 which I am acquainted, I may be permitted to indicate very briefly 

 the plan adopted after a good deal of preliminary investigation.* 



The well-known law of Dulong and Petit, as modified by Can- 

 nizzaro, asserts that the atoms of elementary matter have the same 

 capacity for heat, when Ave compare them in the solid state. The 

 outstanding exceptions to this important law are few, and even these 

 appear to have been cleared away in some degree by the recent re- 

 searches of "Weber on the specific heats of silicon, boron, and carbon. 

 The principle, however, is admittedly sufficiently general in its appli- 



* The preparation of pure metallic glucinum in quantities exceeding t^ro or 

 three grammes is difficult and costly ; for this amongst other reasons, I determined 

 to employ Bunsen's admirable and theoretically perfect ice calorimeter in the esti- 

 mation of the specific heat of the metal, as small quantities of material only are 

 required. It proved, however, to he impossible, owing to various engagements, to 

 prepare the glucinum in a state of sufficient purity until the season had passed 

 when Bunsen's ice calorimeter can be conveniently used. I had, therefore, to 

 devise a calorimetric method which could be employed during warm weather, and 

 which could afford trustworthy results with small weights of material. I have 

 given in the text an outline of this method, but the details of its application to the 

 determination of atomic and molecular heat will form the subject of another com- 

 munication. 



