1819.] Combination of Carbonate and Hydrate of Lime. 51 
and its quantity ascertained. Dissolve the anthrazothionate of 
manganese in water, and precipitate the manganese by means of 
potash. From the oxides thus obtained, we may determine the 
quantity of metal by Berzelius’s method; but this method of 
separating the two metals is not absolutely correct, because 
anthrazothionate of manganese is slightly soluble in alcohol. 
EE EAS LS 
ArTIcLe VIII. 
A remarkable Combination of Carbonate of Lime and Hydrate of 
Lime, observed by Theodor von Grotthuss.* 
WueEN a strong current of carbonic acid gas is suddenly 
passed through lime water, there is formed not a pure carbonate 
of lime, but a mixture of carbonate and hydrate. This fact deserves 
attention, because in many cases it is easy to mistake one of 
these compounds for the other. It is very bulky, and falls slowly 
to the bottom in flocks ; but it has only an ephemeral existence ; 
for as soon as these flocks approach near each other, they lose 
at once their voluminous appearance, and do not assume it again 
when agitated. They have now a granular, powdery consist- 
ence, and a much greater specific gravity, in consequence of 
which they sink rapidly to the bottom, and do not appear in 
flocks. The substance in this last state is pure carbonate of 
lime. If concentrated acetic acid be poured upon the bulky 
precipitate when first formed, not the smallest evolution of air 
bubbles is perceptible ; because the carbonic acid as it is set at 
liberty, finds, in consequence of the great bulk of the hydrate 
and of the water which it contains, so many points of contact 
with it, that it cannot assume the gaseous form. If a concen- 
trated solution of an ammoniacal salt, for example, sal ammoniac, 
be poured into the bulky hydrate, which renders the water as 
white as milk, the liquid becomes immediately almost colourless, 
because the hydrous carbonate passes at once into the state of 
pure carbonate, which last has a very small volume when com- 
cs with the former. Were the bulky precipitate merely a 
ydrous carbonate, we might suppose that the salt deprives it 
of its water ; but a concentrated solution of common salt does 
not, by any means, produce the same appearance. The bulky 
Bete, therefore, must be a compound of carbonate and 
ydrate of lime. The hydrate unites with the acid of the ammo- 
niacal salt and sets the ammonia free, while the pure carbonate 
only remains behind. The action of the water and attraction of 
cohesion of the carbonate of lime, a pear gradually to destroy 
the compound. It has, therefore, as has been already observed, 
* Translated from Schweigger’s Journal, xx. 275. 
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