and the formation of Gypsum and Magnesian Rocks. 175 
sulphate of lime, equal to about 2°0 grms. of carbonate of lime to 
a litre e carbonate of soda in the alkaline filtrate was found, 
by the indirect method of § 12, equal to 434 grm.; theory re- 
quires °432. 
14. In another experiment, a dilute solution of sulphate of 
soda was treated with an excess of bicarbonate of lime, in order 
to determine whether it were possible to decompose completely 
the soda-salt by this means. After throwing down the gypsum 
by alcohol, the residue contained for a litre 1-080 of carbonate 
and 0°520 of sulphate of soda. 
15. 250 c. c. of water, containing ten grams of hydrated sulphate 
of soda, and two grams of pure carbonate of lime, were exposed 
for an hour and a half to a current of carbonic acid gas, and the 
solution was then left for four hours in a covered flask, after 
which 150 c.c. of the clear liquid were mixed with an equal 
volume of absolute alcohol. A copious precipitate was formed, 
which, after twelve hours, was collected ; it was completely solu- 
ble in 200 c. c. of water, from which alcohol threw down ‘343 grms. 
of sulphate of lime, besides a farther portion of °020 grs. from 
the evaporated filtrate, making a total of 863 grs., equal to 2-420 
grs. of sulphate of lime to the litre. 
. c.¢. of a similar solution to the last, gave with alco- 
hol, a precipitate of gypsum, which was readily soluble in water, 
and being thrown down as oxalate, gave an amount of carbonate 
-. lime equal to 1-820 grms. to the litre, or 2-475 of sulphate of 
é. 
17. A current of carbonic acid gas was passed for an hour 
_ and a quarter through a solution containing sulphate of magne- 
_ §la and carbonate of lime. The filtered liquid remained transpa- 
‘Tent many hours exposure to the air; but 200 c.c. of it 
gave with alcohol a precipitate of gypsum, which was collected 
_ after twelve hours and was completely soluble in water, from 
# Which solution the lime was thrown down as oxalate, giving an 
ig %mount of carbonate equal to 1565 grms. or to 2°128 grms. of sul- 
_ phate of lime to the litre. The alcoholic filtrate by evaporation 
__ to dryness over a water-bath, gave a little carbonate of lime, and 
_ &0 amount of carbonate of magnesia equal to 1:100 grms. to the 
_ tre; theory requires 1-312, but it is difficult to separate in this 
4 es whole of the carbonate of magnesia from an excess of 
q or m 
liquids 
hey are ‘wendy saturated solutions. The 
in $15, §16 and § 17, give respectively one 
