GOi REPORT— 1897. 



part of a system. The rise and fall of Taleucy in the linearly arranged elements 

 follows this form : — 



in general terms, therefore, the valency for the eight families is the same as the 

 number of the family. General formulae can be written for the chlorides, oxides, 

 and hydroxides, MC1„, M^O,,, M(OH)„, where M stands for any member of a family, 

 and n for the number of the family. The derivation of the ortho acids and salts, 

 the pyro and meta salts and acids, is shown in Table III., which exhibits the 

 ideal system of compounds which the elements tend to form. The gist of this is 

 not new ; but is not the whole system, exhibited en bloc, more easily comprehended 

 than as usually presented, and would not a chart of this form in the lecture-room 

 rand laboratory simpUfy the matter of naming compounds and reduce a chaos of 

 symbols and names into impressive order ? 



Isomorphism is another physical phenomenon easily shown and appreciated. 

 It is of value because it gives an optical demonstration of the fact that when 

 elements act with similar valency, they show other chemical likenesses, even when 

 they are widely separated in the natural classification, e.g., Ca, Sr, and Ba and 

 dyad manganese ; aluminium, and triad chromium, &c. Tho table of isomorphism 

 becomes much more suggestive if, instead of being arranged in the form in which 

 it is copied from text-book to text^hook, it is set in the following form : — 



Table IV. 



I. Li, Na, Rb, Cs ; T\\ Ag ; Cu', Ag ; Au'. 



il. Ca, Sr, Ba, Pb» ; Mg, Zn, Mn", Fe''; Ni", Co", Cu" ; Cd, Be, In with 

 Zn. 

 Ce», La", Di-', Er", Y with Ca ; Cu'', Hg^' with Tb ; Tl with Pb. 



III. Al, Fe'", Cr»', Mn'» ; Ce"', U'", Ga ; B, N'", Ta ; N'», P»' (in organic 

 bases ?) 



lY. C, Si, Ti, Zr, Th, Sn ; Fe"", Ti. 



V. As, Sb, Bi ; P and V (in salts) ; N and P (in organic bases). 



YI. S, Se, Te (in tellurides) ; Cr, Mn", Te ; Cr, Mo, A\' ; As and Sb in the 

 glances. 



YII. CI, Br, I ; Mn"". 



YIII. Os, Ir, Pt, Ru, Rh, Pd ; Fe, Ni, Au ; Sn, Te. See Ostwald's Outlines. 



A table of solubility may be constructed of such symmetry that it is but a 

 ■slight act of memory to carry all the more important cases used in analysis (see 

 Table Y.). After half an hour's pr.actice with this table the student can pick cut 

 .the soluble and insoluble salts from a page of formulae. 



