1 80 Mr. H. Croft's Abstract of Dr. H. Kopp's Researches 



volume of B, and from the atomic volume of C O that of C. 



For instance, in the case of the oxides : — 



The atomic volume of Pb O = 146, Cd O == 1 13, Zn O = 90 



Pb = 114, Cd = 81, Zn =_58 



32 32 32 



Or for the nitrates : — 

 Atomic volume of Pb W 0<^ = 472, Ag N^ 0« = 488 



Pb = n_4, Ag = 130 



358 358 



For the explanation of the atomic volumes of these bodies, 

 we see that one assuujption as to the atomic volume of one 

 element is quite sufficient. We assume that the metal is 

 contained therein with its primitive atomic volume. In the 

 nitrates we say that the radical N- O" has the atomic volume 



358. 



Dr. Kopp examines first the salts, and divides them into 

 two groups, — salts of heavy metals and salts of light metals. 

 He considers them according to the hydracid theory. 



In the salts of heavy metals he assumes that the metal pos- 

 sesses its primitive atomic volume; but with the salts of the 

 liwht metals this is not possible, for the atomic volumes of the 

 salts are often smaller than the primitive atomic volumes of. 

 the component metals. 



He therefore assumes for the light metals a peculiar atomic 

 volume, which remains the same in all their salts; we will 

 give these atomic volumes in the following table : — 



Ammonium 218 Magnesium 40 



Barium 143 Sodium 130 



Calcium 60 Strontium 108 



Potassium 234 



He determines these numbers in the following manner: — 

 Suppose M + R to l)e a compound of a heavy metal, m + R 

 the analogous compound of a light one. Suppose A to be 

 the known atomic volume of M + R and a that o( m + R, B 

 the primitive atomic volume of M, and b of >w. 

 Then, atomic volume of M + R = A 

 Prim. atom, volume of M = B 



A - B = ,r, 

 the atomic volume with which R is contained in the com- 

 pound. It is assumed that R retains its value in M + R ; 

 and therefore 



Atomic volume of m + R = a 



R = .r 



therefore peculiar atomic volume of m = a — x, which are 

 both known. 



