TRANSACTIONS OF THE SECTIONS. 



71 



specific gravity of the mixture is greater than it would have been had no contraction 

 taken place. 



Assuming the specific gravity of strong liquid acid to be 1'8485 (that of water 

 being 1), we may find what ought to be the specific gravity of any mixture of acid 

 and water, did no contraction take place. 



By Dr. lire's table we can tell the actual specific gravity of such a mixture. 



Dividing this by the former, we have the proportional condensation. 



The proportional condensation is greatest for strength 73 of Dr. Ure's table, which 

 denotes a hydrate composed of 1 equivalent liquid acid and 2 equivalents of water. 



Let us now suppose all mixtures stronger than a given mixture to be formed by the 

 combination of that mixture with liquid acid, and all mixtures weaker than it to be 

 formed by its combination with water. 



If we call this given mixture our standard, and take its specific gravity from Dr. 

 Ure's table, we shall, by means of it, be referred to new proportional condensations 

 diflferent from those already alluded to. 



Taking as our standards strengths 40, 43 and 45, we are referred to a maximum 

 of condensation at strength 73, as before. 



Taking as our standards strengths 50, 53 and 55, we are referred to a maximum 

 between strengths 84 and 85, denoting a hydrate composed of 1 equivalent of liquid 

 acid and 1 equivalent of water. 



Taking as our standards strengths 38, 40 and 45, we are referred to a maximum 

 at strength 82, denoting probably a hydrate composed of 5 equivalents of liquid acid 

 and 6 equivalents of water. 



From this it appears, that were we to use as standards all the 100 strengths in 

 Dr. Ure's table, we should be referred to maxima of condensation the number of 

 which would be much less than 100. May we hot infer, that when liquids or 

 other substances mix with each other in all proportions, all strengths of such mix- 

 tures may be viewed as derived from definite compounds having a tendency to com- 

 bine with their components and with each other, thereby forming other compounds, 

 so that at length mixtures of any strength may be produced 1 



It might be advantageous to lay off the diSerent strengths in Dr. Ure's table as 

 abscissa of a curve, of which the corresponding proportional condensations (for a 

 given standard) are the ordiuates ; thus the irregularities would become apparent. 



It might also be advantageous to apply this analysis to metallic alloys and amal- 

 gams, where it would probably indicate those possessed of properties the most marked. 



On the Condition of the Atmosphere during Cholera. 

 By R. D. Thomson, lU.D., F.R.S. 



The chemical condition of cholera atmospheres is a question of intense interest in 

 the subject of public health ; but, with the exception of the unpublished experiments 

 of Dr. Prout in 1832, comparatively little attention appears to have been bestowed 

 on it. One of the most striking circumstances connected with the occurrence of the 

 disease is, that no change very palpable to the senses prevails, and even one may 

 have remarked that the weather has usually been exceedingly agreeable. In Lon- 

 don, at St. Thomas's Hospital, the neighbourhood of which afforded a large supply of 

 cholera cases, the relative weight of the air in August 1854, a cholera month, and in 

 August 1855, when the metropolis was in an extremely healthy condition, is exhi- 

 bited in the following table, in grains per cubic foot : — 



