Proceedings, 



iii 



R. B, Smythj Esq., said with regard to the maximi of densities, 

 which it was the object of Mr. Stewart's paper to elucidate, he 

 would beg to refer to the following observations of Dr. Ure, who 

 computed the tables on which that paper was founded. 



"Dilute acid having a specific gravity = 1*6321 has suffered the 

 greatest condensation ; 100 parts in bulk have become 92 14. If either 

 more or less acid exist in the compound, the volume will be increased. 

 A¥hat reason can be assigned for the maximum condensation occurring 

 to this particular term of dilution? The above dilute acid consists of 

 73 per cent, of oil of vitrol, and 27 of water. But 73 of the former 

 contains by this table 59*52 of dry acid, and 13*48 of water. Hence 

 100 of the dilute acid consists of 59-52 of dry acid + 13'48 x 3 

 ~ 40.44 of water — 99*96; or, it is a compound of one atom of dry 

 acid, with three atoms of water. Dry sulphuric acid consists of three 

 atoms of oxygen united to one of sulphur. Then each atom of oxygen 

 is associated with one of water, forming a symmetrical arrangement. 

 One may therefore infer, that the least deviation from the above defi- 

 nite proportions, must impair the balance of the attractive forces, 

 whence they will act less efficaciously, and therefore produce less con- 

 densation. 



" The very minute and patient examinations which I was induced to 

 bestow on the tables of specific gravities, disclosed to me the general law 

 pervading the whole, and consequently the means of inferring at once 

 the density from the degree of dilution, as also of solving the inverse 

 proportions." 



Subsequently Dr. Ure gives clear directions for ascertaining the dry 

 acid and sulphuric acid in any dilate acid of given specific 

 gravity. As Dr. lire's tables are dependent upon the nicety of his 

 apparatus, and care in truly estimating the various influences to 

 which experiments with sulphuric acid are liable, we cannot im- 

 plicitly rely upon their accuracy. As a foundation for calculation, 

 such as Mr. Stewart's, he held them to be objectionable. Sulphuric 

 acid, as Dr. Ure observes, has only a small specific heat, and is 

 affected by changes of temperature, which would scarcely be 

 recognised by the most delicate instruments. 



Mr. Smyth considered the subject to be highly useful in a 

 scientific point of view, if tested by actual experiment. 



Presents acknowledged : — Eossils and Minerals from Mount Ida, 

 M'lvor, Capt. Clarke, E.E. 



Septemler ISth, 1854. 

 Special General MsETiNa. The President in the Chair, 



The Minutes of the last Meeting were read and confirmed. 



The Honorary Secretary read the following Report of the Sub- 

 Committee, appointed at the last meeting, to consider the details of 

 the project for organising exploring expeditions: — 



