CHEMICAL ANALYSIS OV SOME CALAMINES. 85 



penfion in the air like that which takes place with camphor'ElucIdations of 

 when, after having been Come time inflamed, it is blown out. '1^=™'"' theory, 



A moment's reflection muft evince, how injudicious is the 

 common opinion, of cryftallizalion requiring a ftate of folution 

 in the malter ; fince it muft be evident, that while folution fub- 

 fifls, as long as a quantity of fluid admitting of it is prefenl, no 

 cryftallization can take place. The only requifite for this opera- 

 tion, is a freedom of motion in the maflTes which tend to unite, 

 which allows them to yield to the impulfe which propels them 

 together, and to obey that fort of polarity which occafions 

 them to prefent to each other the parts adapted to mutual union. 

 No ftale fo completely affords ihefe conditions as that of me- 

 chanical fufpenfion in a fluid whofe denfity is fo great, rela- 

 tively to their fize, as to oppofe fuch refiftance to their defcent 

 in it as to occafion their mutual attraction to become a power 

 fuperiorto tlieir force of gravitation. It is in thefe circumftances 

 that the atoms of matters find themfelves, when, on the fepa- 

 ration from them of the portion of fluid by which they were 

 diflolved, they are abandoned in a difengaged flate in the 

 bofom of a folulion ; and hence it is in faturated folutions fuf- 

 taining evaporation, or equivalent cooling, and free from 

 any perturbing motion, that regular cryftallization is ufoally 

 eflfeded. 



But thofe who are familiar with chemical operations, know 

 the fort of agglutination which happens between the particles 

 of fubfided very fine precipitates : occafioning them^ on a 

 fecond diffufion through the fluid, to fettle again much more 

 quickly than before, and which is certainly a cryftallization, 

 but under circumftances very unfavourable to its perfe6l per- 

 forrnance. 



5. No calamine has yet occurred to me which was a real, 

 uncombined, calx of zinc. If fuch, as a native produft, fhould 

 ever be met with in any of the ftill unexplored parts of the 

 earth, or exift amongft the unfcrutinized pofl'efiions of any 

 cabinet, it will eafily be known, by producing a quantity of arid 

 vitriol of zinc exadly double its own weight ; while the hydrate 

 of zinc, fhould it be found fingle, or uncombined with the car- 

 bonate, will yield, it is evident, 1.5 its weight of this arid fait. 



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