PSEUDOMORPHISM, ETC. T>;> 



(like- form) * peculiarities are exceedingly common, and 

 the discoverer of the phenomena, Mitscherlich, an- 

 nounced the above law. It cannot, however, be regarded 

 as a philosophical expression of the fact, and requires 

 reconsideration chemical elements of a dissimilar cha- 

 racter may have the same law of aggregation, and thus 

 produce the same form, without having any relation to 

 the number of atoms. 



We also find compounds which have two distinct 

 systems of crystallisation. This property, Dimorphism, 

 is very strikingly shown in carbonate of lime, which 

 occurs in rhombohedrons, in calc spar, and in rhombic 



* " Gay Lussac first made the remark, that a crystal of potash 

 alum, transferred to a solution of ammonia alum, continued to in- 

 crease without its form being modified, and might thus be covered 

 with alternate layers of the two alums, preserving its regularity and 

 proper crystalline figure. M. Beudaut afterwards observed that 

 other bodies, such as the sulphates of iron and copper, might pre- 

 sent themselves in crystals of the same form and angles, although 

 the form was not a simple one, like that of alum. But M. Mits- 

 clicrlich first recognised thisjcorrespondenee in a sufficient number 

 of cases to prove that it was* a general consequence of similarity of 

 composition in different bodies." Graham's Elements of Che- 

 mistry (1842), p. 136. 



The following remarks are from a paper by Dr. Hermann Kor>^, 

 On the Atomic Volume and Crystalline Condi' ion of Bodies, Sfc., 

 published in the Philosophical Magazine for 1841 : " The doctrine 

 of isomorphism shows us that there are many bodies which pos- 

 sess an analogous constitution, and the same crystalline form. 

 Our idea of the volume (or, in other words, of the crystalline form) 

 of these bodies must therefore be the same. From this it follows 

 that their specific weight is connected with mass contained in the 

 same volume. From these considerations the following law may 

 be deduced : The specific weiyht of isomorphous bodies is propor- 

 tional to their atomic weight, or isomorphous bodies possess the same 

 atomic volume.'' page 255. A translation appears in the Caven- 

 dish Society, from Dr. Otto's Chemistry, On Isomorphism, which 

 may be advantageously consulted. See also a paper by M. Hose, 

 translated from the Proceedings of the Royal Berlin Academy for 

 the Chemical Gazette, Oct. 1848, entitled, On the Jsomeric Condi- 

 tions of the Peroxide of Tin. 



