REPORT ON CHEMISTRY. 
427 
On this list it is to be remarked,— 
1 °. That the isomorphism of the several groups of the ele¬ 
mentary substances, with the exception of the first four of those 
constituting group I., is inferred from that of their compounds 
with an equal number of atoms of oxygen. 
2 °. That the groups I. IV. VIII. IX. are connected to each 
other by one or two links, which render it highly probable that 
these and all other elementary substances will prove isomor- 
phous, conformably to Mitscherlich’s law, quoted in page 4 22. 
Manganese forms the link between the groups I. IV. and VIII.; 
the hypermanganic being isomorplious with the hyperchloric 
acid; the manganic with the chromic, and the protoxide and 
peroxide of manganese with the protoxide and peroxide of iron. 
3°. The connexion between groups VIII. and IX., by the 
elements calcium and lead, will be explained more fully under 
the head of Isodimorphous Bodies. 
4°. The three bases constituting group XV. form isomor- 
phous compounds with the hydracids. 
5°. Gold and silver have been selected (XVII.) from the 
other electro-positive metals, because G. Rose has lately esta¬ 
blished their isomorphism by an extensive examination of their 
secondary forms; they are probably isomorphous with all the 
other electro-positive metals, but no measurements have yet 
been made of their secondary forms. Sodium is added to the 
same group, in consequence of the identity of form of the sul¬ 
phate and seleniate of silver, and the anhydrous sulphate and 
seleniate of soda, as shown by Mitsclierlich. 
Besides these groups of isomorphous elements and binary 
compounds, other instances of identity of form have been ob¬ 
served, which cannot be comprised w r ithin these groups. 
Thus one of the forms of sulphur is identical with those of 
the bisulphate and biseleniate of potash. 
Relation of the forms of Potash and Soda .—The form of 
the nitrate of potash and those of the carbonates of barytes, 
strontian and lead, are alike: 
While nitrate of soda is isomorphous w r ith the carbonates of 
lime, magnesia, and the other bases in group V. 
From these two latter observations on the alkaline nitrates, 
it appears that soda and potash have the same relation to each 
other as the bases included in groups VIII. and IX. 
Forms of Mineral substances .—In the mineral kingdom, 
bodies belonging to the same isomorphous group are occa¬ 
sionally met with in identical forms, thus confirming the con¬ 
clusions drawn from the isomorphism of their similar com¬ 
pounds. Thus w r e have 
