418 Rev. J. B. Emmett on the Specific Gravity of Compounds. 



pear, that, with the exception of the deutosulphuret of iron, 

 there is a great expansion during combination ; or that the 

 compound is much lighter than it ought to be, according to 

 calculation ; whereas the calculated, except that of the proto- 

 sulphuret of arsenic, is always less than the true density; which 

 by analogy might be expected. 



The same philosopher has constructed a table of the speci- 

 fic gravity of certain saline solutions. (See Thomson's Che- 

 mistry, vol. iii, p. 97.) He gives the weight of the salt; the 

 specific gravity of a saturated solution; the proportion of the 

 ingredients; and the specific gravity of the salt in the solu- 

 tion, supposing, in all probability, that the salt alone suffers 

 expansion or contraction during solution ; or calculating what 

 must be the specific gravity of the salt, did no expansion or 

 contraction take place. I have calculated a few of the numbers 

 by the above formula. 



Sulphate of Potash. Diff. 



Hassenfratz's computation 1*859 — "S-tSS 



True specific gravity 2*4073 



Computed by Newton's formula 5*39 +2*9827 



Muriate of Baiytes. Diff. 



Hassenfratz 1*937 — '889 



True gravity 2*826 



By Newton's formula 3*84 +1*014 



Muriate of Zinc. Diff. 



Hassenfratz 1*773 + -196 



True gravity 1*577 



Newton's formula 1*925 + "348 



Nitrate of Potash. Diff. 



Hassenfratz 1*628 — *3089 



True gravity 1*9369 



Newton's formula 2*19 + *1531 



In these cases, which might easily be multiplied, there is a 

 manifest condensation during solution : however, no precise 

 conclusions can be drawn until the specific gravity of crystal- 

 lized salts shall be determined by a method which is free from 

 sources of fiillacy. 



In the following table I have given the specific gravity of 

 saturated solutions of various neutral salts, experimentally as- 

 certained, from Thomson's Chemistry, vol. iii. p. 97, and the 

 density calculated by Newton's formula. 



By inspection, it is manifest that condensation takes place 

 in all cases, except those marked + : yet, since the specific 

 gravity of the salts is probably in most cases greater than that 



given 



