24 



M. J. A. Groshans on the 



Again, comparing the pairs Hg and Zn, which are diad in 

 compounds such as Zn(C 2 H 5 ) 2 , and Pb and Sn, which are 



Table VIII. 



Atomic 

 weight. 



Density- 

 number. 



Atomic 

 weight. 



Density- 

 number. 



Zn 65 



135 

 Hg 200 



11 



15 

 26 



Sn 118 



89 

 Pb207 



14 



15 

 29 



tetrad in corresponding compounds, we find that in the first 

 pair, where the difference in the atomic weights 135 =3 x 45, 

 that in the density-numbers = 15 = 3 x 5 ; but that this is 

 not the case with lead and tin ; for while the difference in 

 atomic weights ( = 89 = 2x45) is double, the difference in 

 density-numbers is treble. In time, I trust, as the gaps in 

 Table I. are filled up, it will be possible to extend and 

 generalize considerations of the above nature. 



After this digression I shall return to the application of the 

 law to hydrated crystals, and shall apply it to the results of 

 the well-known experiments of Schiff on the density of alums 

 and isomorphous sulphates. 



Table IX. 

 Experiments of Schiff. 



Salts. 



B. 



9. 



k. 



(a) Alums: — 



A IK (S0 4 ) 2 12H.,0 



AlNa(SO t )., „ 



OrK(S0 4 ); „ 



57 

 56 

 62 



1-722 

 1-641 

 1-845 



331 

 341 

 336 



(b) Sulphates: — 



McSO, 7H o 



32 



38 

 38 

 38 

 36 



1-685 

 1-953 

 1-931 

 1-924 



1-884 



19-0 

 19-5 

 197 



19-8 

 191 



ZnS0 4 „ 



Ni S0 4 „ 



CoSO t „ 



FeS0 4 „ 



(c) Double Sulphates : — 



MgK 2 (S0 4 ) a 6H a O 



ZnK 2 {8Q\ „ 



NiK^SOJa .» 

 CoJQSOJ., ,, 



FelCtSOj: „ 

 CdK o (S0 4 ): „ 



Cuk;(so 4 ) 2 „ 



45 

 51 

 51 

 51 

 49 

 56 

 51 



1-995 

 2153 

 2123 

 2-154 

 2-189 

 2438 

 2-137 



22-4 

 23-7 

 24 

 23-7 

 22-4 

 23-0 

 23-9 



