XVII.] CONSTITUTION AND VOLUME OF MINERAL SPECIES. 441 



ferrocyanide of potassium with C^ = 230, and lactose with 

 C.J4 = 234 ; the equivalent weight of carbon being 6. 



[An attempt was then made to fix the volume of the pris- 

 matic and rhombohedral carbon-spars, which were compared re- 

 spectively with the isomorphous species bournonite and the red 

 silver ores, proustite and pyrargyrite. The received formula 

 of bournonite being doubled, and that of the rhombohedral sul- 

 phides made to correspond with it, we find for the prismatic 

 species an equivalent volume of 508, and for the rhombohedral 

 ones 546-564 In accordance with this the equivalent of 

 calcite corresponds to CsoCagoOgo (C = 6 and = 8), while 

 dolomite, chalybite, and diallogite become C^M^O^, and cala- 

 mine and magnesite C^M^O^. For the prismatic carbonates, 

 aragonite, like calcite, is C^MgoOgo, while strontianite, ceru- 

 site, and bromlite are C^M^C^, and witherite is C^M^O^. 

 With these were at the same time compared the homoeo- 

 morphous rhombohedral and prismatic nitrates of soda and 

 potash, from which it was suggested that the above equiva- 

 lents were to be still further multiplied. That the volume 

 above fixed for these rhombohedral species was, if not the true 

 one, a rheasure of it, was soon rendered more probable by an 

 examination of the compound of glucose and chloride of 

 sodium, which was obtained in large rhombohedral forms 

 isomorphous with calcite and having a density of 1.563. 

 Doubling the empirical formula of this body, 



C*H M 0.:NaCl . H 2 2 



we have for it an equivalent volume of 558.5, while that of 

 calcite with CgoMgoOgo, and a density of 2.72 = 555.5. (Amer. 

 Jour. Science (2), XIX. 416.) 



[From Glauber-salt and borax were deduced, in like manner, 

 an equivalent volume of about 440, corresponding nearly with 

 that of saccharose with C^ = 430, and with these were com- 

 pared the silicates of the amphibole group, from which it was 

 concluded that these silicates present among themselves rela- 

 tions similar to those of the homceomorphous carbon-spars. 

 The attempts to deduce correct formulas for these and other 

 silicates at that time were, however, vitiated by many incorrect 

 19* 



