194 Scheerer on Isomorphism. 
5. Copper Mica. 
The composition of the Cornish copper mica, according to 
Chenevix, is arsenic acid 21, oxyd of copper 58, water 21 = 100, 
corresponding to the oxygen ratio, 7°29 ‘As : 11-70Cu : 18°67 H, . 
which may be likewise thus expressed, 729.As : 15-00Cu: 
12-07 H, representing pretty closely the formula, 2(Cu)! ° As+ 
15H, which requires the oxygen ratio, 7‘50 : 15-00 ; 11:25. 
6. Lenticular Copper. 
Rammelsberg proposes for this mineral, as analyzed by Chene- 
vix, the formula, Cu’ As+30H, which represents very closely 
the result of that analysis, and harmonizes well with the formula 
proposed for the preceding mineral. ‘This formula can be also 
expressed as follows, 4(Cu)! . As +308. 
V. SuLpHates. ® 
“ 1. Melanterite. 
According to Mitscherlich, the formula of sulphate of iron is 
7m. The former formula, taking 3£ = 1Fe; may be converted 
to (Fe)? S, and the latter to (Fe)*S+H. Since protoxyd of 
iron and water appear to exist always in sulphate of iron in de- 
terminate proportions, the former formula, properly speaking, may y 
Fe S+6H. According to Graham, on the contrary, it is Fe S+ f 
i 
be expressed more correctly thus, Fe? S+2()5 S, and the latter 
also in the same manner, but with + #. 
2. Epsomite. (Beudant. ) 
The formula thereof is Mg$+7x, which is convertible to 
» 
(Mg)* S+H, the remarks appended to melanterite being likewise 
applicable in this case. 
3. Gloslarite. (Haidinger. ) 
Its formula is Zn S-+73, which is equivalent to (Zn)? 8 +H. 
4. Bieberite. (Haidinger.) 
The sulphate of cobalt from Bieber consists, according to Win- 
kelblech, of sulphuric acid 29-05, protoxyd of cobalt 19-91, mag- 
