VOL. LXXI.] PHILOSOPHICAL TRANSACTIONS. 3 



II. Experiments and Observations on the Specific Gravities and Attractive Powers 

 of various Saline Substances. By Richard Kirwan, Esq., F.R.S. p. 7- 



The doctrine of" chymical affinities has received great improvements from the 

 labours of Mr. Bergman of Upsal, and the still later researches of Mr. Wentzel ; 

 but the order of these attractions has hitherto been the only point attended to 

 by these philosophers, as well as by most preceding chymists ; for I know of 

 none (says Mr. K.) except Mr. Morveau of Dijon, who has thought of ascer- 

 taining the various degrees of force of chemical attraction, by which one body 

 acts on various other bodies, or even on the same body in various circumstances. 

 He has however so ably shown the advantages arising from such an inquiry, that 

 I have made it the object of my attention, and bestowed much pains on it for 

 s.ome time past ; and have thence been enabled to determine pretty exactly the 

 proportion of the ingredients of many neutral salts, and the specific gravity of 

 the mineral acids in their purest state, and free from all water. The principles 

 on which these determinations are founded are the following. 



1st. That the specific gravity of bodies is as their weight, divided by the 

 weight of an equal bulk of rain or distilled water, this being at present the 

 standard with which every other body is compared. 



2dly. That if bodies, specifically heavier than water, be weighed in air and in 

 water, they lose in water part of the weight they were found to have in air ; 

 and that the weight so lost is just the same as that of an equal bulk of water, 

 and consequently that their specific gravity is equal to their weight in air, or ab- 

 solute weight, divided by their loss of weight in water. 



3dly. That if a solid, specifically heavier than a liquid, be weighed first in air, 

 and then in that liquid, the weight it loses is equal to the weight of an equal vo- 

 lume of that liquid; and consequently if such solid be weighed first in air, then 

 in water, and afterwards in any other liquid, the specific gravity of this liquid 

 will be as the weight lost in it by such solid, divided by the loss of weight of the 

 same solid in water. This method of finding the specific gravity of liquids I 

 have found much more exact than that by the areometer, or the comparison of 

 weights of equal measures of such liquids and water, both of which are subject 

 to several inaccuracies. 



4thly. That where the specific gravity of bodies is already known, the weight 

 of an equal bulk of water may also be found, it being as the quotient of their 

 absolute weight divided by their specific gravity. This I shall call their loss of 

 weight in water. 



Hence, where the specific gravity and absolute weight of the ingredients of 

 any compound are known, the specific gravity of such compound may easily be 

 calculated, as it ought to be intermediate between that of the lighter and that of 

 the heavier, according to their several proportions: this I call the mathematical 



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