PATENT FOR THE MANUFACTURE OF EPSOM SALTS. 231 
tion. In general the improved essence has been found to 
boil at 310°, whilst before its distillation its boiling point 
varied from 312° to 316° F. I analysed the modified oil, 
and found that its composition was exactly the same as that 
of the primitive essence, — Chemist, from Bulletin da 
Musee dt V Industrie. 
ART. LI.— PATENT GRANTED TO J. B. GREGSON, DUNSTON, 
DURHAM, FOR IMPROVEMENTS IN THE MANUFACTURE 
OF EPSOM SALTS AND CARBONATE OF LIME, COMMONLY 
CALLED PRECIPITATED CHALK, PARTS OF WHICH IM- 
PROVEMENTS ARE APPLICABLE TO OTHER PURPOSES. 
These improvements in the manufacture of epsom salts 
are two in number, and consist, — 1st, in the application of 
sulphuric acid to dolomite or magnesian limestone in the 
uncalcined state ; and 2d, in the application of muriate of 
ammonia to remove the lime from the mixed hydrates of 
lime and magnesia, obtained by thoroughly calcining and 
slaking dolomite. 
The following is the mode of carrying out the first im- 
provement : — The dolomite is reduced to powder, and made 
into a paste with water, in an open vessel lined with lead ; 
then sulphuric acid, of 1.500 spec, grav., is added in the pro- 
portion of 350 lbs. of the latter to 200 lbs. of the former, and 
the mixture is well-stirred. The sulphuric acid rapidly de- 
composes the dolomite, and carbonic acid gas is liberated . 
and when the effervescence ceases, a solid substance re- 
mains, composed of the sulphate of lime and magnesia; if 
desired, the carbonic acid gas may be collected for use, by- 
mixing the sulphuric acid and dolomite in a close vessel. 
