232 PATENT FOR THE MANUFACTURE OF EPSOM SALTS. 
The mixed sulphates are separated by diffusing the solid 
residuum in water, allowing the sulphate of lime to subside, 
and drawing off the supernatant liquid, which is a solution 
of sulphate of magnesia, (epsom salts,) containing"" a small 
quantity of sulphate of iron ; this solution is freed from sul- 
phate of iron by means of caustic lime or magnesia, and is 
evaporated and crystallized in the usual way. Or the mixed 
sulphates may be calcined in a reverberatory furnace for 3 
or 4 hours, or until the whole of the iron isperoxidized ; and 
when this has been done, the sulphate of magnesia may be 
dissolved out of the mass, and the clear solution evaporated 
and crystallized. 
The method of operating according to the second improve- 
ment is as follows : — 200 lbs. of muriate of ammonia are 
dissolved in 100 gallons of water, in an iron boiler, by the 
application of heat, and the solution is allowed to cool ; after 
which 200 lbs. of thoroughly calcined dolomite are slaked 
with water, and put into an iron still (holding from 300 to 
400 gallons,) connected with a Woulf's apparatus contain- 
ing water; the solution of muriate of ammonia is then in- 
troduced, and a gentle heat applied to expel the ammonia, 
which is condensed in the Woulf's apparatus, and stored 
for use. When all the ammonia has come over, the resi- 
duum is withdrawn from the still, and the hydrate of mag- 
nesia thoroughly washed, to free it from muriate of lime. 
The magnesia is then saturated with sulphuric acid, the iron 
it contains is thrown down by means of caustic lime or mag- 
nesia, and the clear solution is evaporated and crystallized. 
The improvements in the manufacture of carbonate of 
lime consist, — 1st, in the application of carbonic acid gas to 
a solution of caustic ammonia and muriate of lime, and in 
the recovery of the muriate of ammonia for subsequent use', 
and 2d, in adding a solution of carbonate of ammonia 
(obtained by saturating a solution of caustic ammonia with 
carbonic acid gas) to asolutionof muriate of lime. 
With regard to the first improvement, the operation is 
