Intelligence and Miscellaneous Articles. 401 



ON METALLIC CARBONATES. BY M. J. LEFORT. 



The author obtained the metallic carbonates which he examined 

 by treating the salts with neutral alkaline carbonates and bicarbo- 

 nates, both cold and hot. 



Carbonate of Manganese obtained by the above methods is always 

 represented by C0 2 + MnO-fHO. When heated it begins to lose 

 water at about 1 94° F ; it may be rendered perfectly anhydrous 

 without any notable change of colour ; it does not absorb oxygen 

 below 576° F. ; it is a white powder with a rose tint. 



Carbonate of Cadmium. — Almost all treatises on Chemistry gives 

 C0 2 +CdO as the formula of this compound ; the author's analyses 

 prove that it always contains 4 to 5 per cent, of water, or half an 

 equivalent ; this it loses between 180° and 248° F. Its composition 

 is then 2CO°- + CdO + HO. 



Carbonate of Nickel. — Oxide of nickel forms three perfectly defi- 

 nite compounds with carbonic acid : — 



1 . A basic carbonate whenever cold solutions of the salts of nickel 

 are precipitated by cold solutions of neutral carbonates. It is of an 

 apple-green colour, and represented by 2C0 2 +5NiO + 8HO. 



2. A sesquibasic carbonate; the colour very nearly resembles that 

 of the preceding ; it is formed when the salts of nickel are treated 

 with bicarbonates. Its formula is 2C0 2 + 3NiO + 6HO. 



3. A pentabasic carbonate, which may be prepared by boiling the 

 two preceding salts, or still better precipitating the hot solutions of 

 the salts of nickel by neutral carbonate of potash or soda. Its 

 colour is meadow-green, and its formula C0 2 + 5NiO + 5HO. 



Carbonate of Chromium. — The salts of sesquioxide of chromium 

 give with the alkaline carbonates and bicarbonates, sometimes a^pe- 

 culiar hydrate, and sometimes a definite compound represented by 

 C0 2 +Cr 2 3 + 4HO. When sulphuret of chromium of the green 

 variety is treated with a neutral or alkaline bicarbonate, all the car- 

 bonic acid is disengaged, and hydrate of sesquioxide of chromium is 

 at the same time precipitated ; but if the operation be conducted 

 with a salt of the violet blue modification, the salt formed is always 

 that of the above-stated composition. 



Carbonate of sesquioxide of chromium, exposed to the action of 

 heat, loses at about 167° F., 19*58 per cent, of water, which cor- 

 responds to three equivalents ; it does not lose its last equivalent of 

 water and its carbonic acid till heated to above 572° F. 



Carbonate of Bismuth exists in the anhydrous and hydrated state. 



It is anhydrous whenever a salt of bismuth, as neutral as possible, 

 is treated with an alkaline carbonate either cold or hot ; no carbonic 

 acid is evolved, and the precipitate formed has always the formula 

 CO 2 Bi 2 O*. But if instead of a neutral carbonate a bicarbonate is 

 employed, much acid is disengaged, and a white precipitate, much 

 lighter than the preceding, is obtained, represented bv C0 2 Bi 2 3 + 

 HO ; it loses its equivalent of water at 212° to 248° F. 



Carbonate of Lead. — Carbonate of lead obtained by treating a salt of 

 lead with a neutral or bicarbonated alkali, possesses, as has been long 

 known, the formula C0 2 + PbO ; but when hot solutions are used, the 

 composition is very different, and represented by 2C0 2 + 3PbO + HO. 



