Atomic Vokime and Specific Gravity. A$5 



gree connected with the law of gaseous volume. We tliere- 

 fore thought it desirable to enter into a series of inquiries on 

 this most important subject, and we have now the honoup tb 

 lay before the Society the First Part of these researches, i*^ 

 .-J; Hitherto the inquiry has been principally confined lo solid 

 bodies, on the just ground that their diminished rate of ex- 

 pansion offers less difficulty to the discovery of the law regu- 

 lating volumes. But there is an objection to the use of so- 

 lids, which to a certain extent counterbalances this advantage, 

 viz. that tliey do not present matter in a perfectly uniform 

 condition, free from cohesion. On consideration, therefore, we 

 were led to believe this objection to be so powerful, that we 

 conceived it to be preferable, so to se}iarate the particles of 

 the body under examination, as to destroy their cohesion, 

 without at the same time altering their chemical properties. 

 Solution in water was the obvious means of effecting this 

 purpose, according to the notions generally entertained of so- 

 lution, and it was therefore resolved to experiment princi- 

 pally upon soluble bodies of well-known and defined constitu- 

 tion. At the same time, it was necessary to examine the re- 

 lation of the solid volume to the volume of the body when in 

 solution, so as to indicate the connection between the solid 

 and the liquid atom. 



The specific gravities of salts are little known, and even 

 when recorded are described so differently by different ob- 

 servers, that it was necessary to determine the specific gravity 

 in each of the cases upon which the experiments were insti- 

 tuted. Hitherto the volumes of solids had always been re- 

 ferred to an equal volume of water; in other words, the solid 

 form of matter had been reierred to its liquid form. This dif- 

 ference of conditions was no small impediment to the discovery 

 of a law which might beVmodified for each form of matter*. 

 By determining the volume of the substance in solution, we 

 compared it in its liquid state to the liquid form of matter in 

 which it was dissolved; and by contrasting the volume of the 

 solids with each other, and also with their volume when ren- 



♦ Before leaving the notice of the labours of those who have preceded 

 'tis in inquiring into the nature of specific gravity, we must not omit to no- 

 tice the speculations of the ingenious Persoz, who (in vol. xl. of the 

 Ann. de Ch. et de Phys., p. 119) drew attention to the equality in volume 

 of isomorphous bodies, and even of some which were not isomorphous. 

 Persoz also believes that the volumes of all bodies are multiples of 56, or 

 half the atomic weight of water ; but this idea does not agree with recorded 

 observations, and is directly contradicted by accurate estimations of spe- 

 cific gravities. — See the work of M. Persoz, Introduction h V Etude de la 

 Chimie Moleculaire, page 834 et seq. 



