On the rule for obtaining atomic volumes. 601 



they should all be brought to the same degree of liquidity, 

 i. e. they should not be lieated or cooled above or below the 

 point of liquidity, or in the same relative state as water at 32°. 



Let us again take the rule before alluded to, and ascertain 

 the relative volumes of the atoms of oxygen and of mercur}'; 

 the specific gravities of these two elements at the same tem- 

 perature will be, oxygen '00134, and mercury 13'545; if we 

 divide their atomic weights by these specific gravities, we ob- 

 tain for the atomic volume of oxygen 5970, and for that of 

 mercury 14*91 : now are we to conclude from this that the 

 ultimate atom of oxygen fills a space 400 times the size of one 

 of mercury? I think not; for if we could liquefy the oxygen 

 gas and also reduce the mercury to —39°, and then take their 

 specifie gravities in this state, it is not altogether improbable 

 to suppose that their atomic volumes might approach equality. 



Again, if we take the two isomorphous elements, iodine 

 and chlorine, we find one in the solid, and the other in the 

 gaseous state ; if we take their specific gravities in these states 

 at the same temperature, that of iodine will be 4'948, and that 

 of chlorine '00305; divide their atomic weights by these spe- 

 cific gravities, and we obtain 25*58 for the atomic volume of 

 iodine, and 1 1 '629 for that of chlorine. What analogies or 

 laws can be deduced from this result? But if we liquefy the 

 chlorine and then take its specific gravity as 1*380, then its 

 atomic volume will be 25*70, approaching to within 0*12 of the 

 other; and is it unreasonable to suppose that if we reduced 

 the iodine also to the liquid state, that the atomic volumes 

 might approach still nearer, if not exactly coincide? and yet 

 what reason can be assigned why, if we liquefy the chlorine, 

 we should not also liquefy the iodine ? 



Several ways have occurred to me of manipulation to pro- 

 cure the specific gravities on the principle I have proposed. 

 For those bodies liquefiable in glass vessels, the common spe- 

 cific gravity bottle might be employed ; of course the water 

 used as the standard must be at 32°; having obtained this 

 standard in the usual manner, the bottle may then be filled 

 with the substance operating on and heated to liquefaction, 

 adjusted while liquid so as to occupy the same bulk as the 

 standard water, allowed to cool, and then weighed. For sub- 

 stances that cannot be melted in glass vessels some other means 

 must be adopted ; perhaps a metallic hydrometer might be 

 constructed to insert into the liquid metal. 



The process would require variation to meet all the variety 

 of the elementary bodies, and would be both tedious and la- 

 borious, but of course it would have only to be ojice correctly 

 performed. 



