REPORT ON CHEMISTRY. 
48 i 
preserved its original form, but by the action of heat had been 
converted externally into the rhomboidal carbonate of lime. It 
was found among the detritus of Mount Vesuvius, and it would 
appear that it had fallen among the lava, the long-continued heat 
of which had induced a new arrangement of the particles, but 
had ceased before the whole crystal had undergone the change. 
An analogous change of arrangement is exhibited in those 
crystals of augite and hornblende mentioned by Gustaf Rose 
in his admirable paper * on the identity of these two mi¬ 
nerals, in which a kernel of the one form is contained within 
a crystal possessing externally the characteristic form of the 
other. 
Hydrated carbonate of lime. —Becquerelf and Gay-Lussac 
have examined the artificial crystals of carbonate of lime, 
which are formed when a solution of quick-lime in sugar, mu¬ 
cilage or starch, is exposed to the air, or is acted on in close 
vessels by a weak galvanic energy. Gay-Lussac employs one 
part quick-lime, three of sugar, and six of water, and in forty- 
eight hours obtained a considerable quantity of crystals ; and 
in two months no lime remained in solution. The crystals are 
white, tasteless, insoluble in water, effloresce in air of 30° C., 
have a specific gravity of 1*788 at 10° C., and crystallize in rhom¬ 
boidal prisms. They contain 47*08 per cent. = 5 atoms water. 
Boiling alcohol takes up two atoms of the water, without 
changing the form of the crystals, which, however, effloresce 
now more rapidly than when they contain five atoms. 
Hyposulphite of barytes. —The hyposulphite of barytes has 
been analysed by Rose J, and its composition found as in the 
o • 
formula (2 S + 2 O) +B + H. When this salt is decomposed by 
heat in close vessels, a sulphate and a sulpliuret are formed: 
sulphur is sublimed, sulphuretted hydrogen is given off, and a 
portion of the water passes over undecomposed, presenting the 
remarkable circumstance of no less than five different products 
from the decomposition of an inorganic body, composed of four 
elements. 
Carbonate of lead.-—I have lately analysed and described § 
under the name of Plumbo-calcite a mineral crystallizing in the 
primitive form of the carbonate of lime, but which consists of 
92‘2 carbonate of lime, and 7*8 carbonate of lead. This proves 
that carbonate of lead is also capable of assuming two forms, 
which are respectively isomorphous with those of carbonate of 
lime. 
* Poggendorf’s Ann. xxii. p. 321. f Ann. de Ckim. xlvii. p. 9; xlviii. p. 301. 
+ Poggendorf’s Ann. xxi.p. 410. § Brewster’s Journ ., N. S., vi. p. 79. 
2 H 
