BSH Soa ag OT Bes Seas iy a ea are ae D 
T. S. Hunt on Lime and Magnesia Salts. 59 
retaining all its carbonate of magnesia. When the recent solu- 
tion is boiled there is formed a i seo precipitate of ei 
of magnesia, with some lime, and after evaporation to drynes 
in a water-bath, a portion of soluble lime-salt remains in the 
residue. 
$92. The transparent crystals which are slowly deposited 
from these solutions contain neither magnesia nor sulphurie 
acid. At low w temperatures they are permanent in the air, but 
when heated to about 30° C. change into an opaque pasty mass. 
Analysis gives for their composition, carbonate of lim 
water 47°7. These crystals agree in their physical chaveeeve 
with the stg mor carbonate of lime, C,Ca,O,, 10HO, which 
requires water 47° 
9 s shown in §75, precipitated and even crystalline car- 
bonate of lime is permanently soluble to a large extent in solu- 
tions of sulphate of soda or of magnesia in presence of an excess 
of ssi acid, in which case sulphate of lime and bicarbonate 
of soda or of magnesia result from double decomposition. This 
process is, however, entirely different from the ready dissolving 
Me recently precipitated and as yet unaggregated carbonate of 
me in solutions of sulphate or chlorid of magnesium which 
solutions of the carbonate of lime. The difference in the condi- 
tion of the lime in the two cases is readily shown by the action 
of alcohol, which from the first solutions at once precipitates the 
whole of the lime as gypsum, and from the second separates it 
no less completely in the form of carbonate. It suffices, how- 
ever, in the second case to saturate with carbonic acid before the 
addition of alcohol to reproduce the ee vs the first case, 
and stig instead of carbonate, sulphate of lim 
94. The solubility of the yet uncondensed arbi et of lime 
in neutral sot power are without action upon it in another 
state of aggregation, 1 a good example of the modified frtinsse 
bo 
of the solutions thus obtained affords an instructive instance 
the influence of time on chemical changes. 
§95. I have found that monocarbonate of magnesia is still 
more soluble than monocarbonate of lime under the conditions 
described, and have in this way obtained more than 5:0 gr. of 
carbonate of magnesia in solution in a liter of water holding 
six per cent of hydrated sulphate of magnesia and a little chlo- 
rid of sodium. ‘This solution, strongly alkaline in its reactions, » 
gave, when gently heated, a or ri een which was 
almost wholly dissolved after some hours repose in the cold. I 
have already shown (§ 23) Sand Satna sulphate of magne- 
