710 REPORT—1863. 
with other substances. Alum and sulphate of alumina are also made from 
sulphuric acid and clay or shale, but the quantities are not very large. The 
quantities produced annually are as follows :—Alum, &c., 4000 tons; rough 
Epsoms, 1800 tons. Some improvements in the details have been introduced 
to economize labour and save materials. The precipitation of the iron from 
aluminous liquors by means of prussiate of iron was first employed here by 
Messrs. Lee and Co.; and the Guisborough Alum Company have introduced 
an aluminous cake, containing sulphate of magnesia, which has been found 
to answer very well in dyeing certain colours, as browns, blacks, d&c., and in 
the manufacture of all kinds of coarse paper. . 
Epsom Salts—The abundant supply of magnesian limestone on the coast 
of Marsden, three miles south of the Tyne, and at other places in the county 
of Durham, has for many years sustained the manufacture of sulphate of 
magnesia on the Tyne. The mineral is a tolerably pure double carbonate of 
lime and magnesia, containing about 21 per cent. of magnesia. The follow- 
ing is an analysis by Mr. Clapham :— 
Per cent 
Pilichn AV slik. BRR OORL Re 10:00 
Alumina £94,336 8.08 se ee 1:60 
Owide. of nonwss 2h tk, Sse 0-50 
Carbonate of magnesia ........ 35°33 
Carbonate of lime ............ 52-50 
99°93 
The process formerly employed was to calcine the limestone, and wash it 
repeatedly with water, by which, however, the lime is only imperfectly 
remoyed, the residue being dissolved in acid and crystallized. The principal 
source of sulphate of magnesia for many years past has been the rough 
Epsoms obtained from the residual mother liquors of the Yorkshire Alum 
Works. In these salts protoxide of iron replaces a variable proportion of 
magnesia, forming a double salt, and an excess of sulphuric acid is always 
present. 
The following is an analysis of rough Epsom salts by Dr. Richardson :— 
Per cent, 
Solphuric agid.,~):\. «oi¢ babu Pe - 32°26 
BM apRON a. .bs - wxnds. ‘ler $65 eeeivaes 15°35 
Protoxide Of Anon. cewidcclivswicie 1-73 
Oxides of nickel and cobalt...... 012 
LAT eg Se I, ee 0:09 
"ALTMIRS dre adowugare auyste Hale Mlle 1:33 
ROAR ee a taatatc mee Ch. tw este oxke hs 0-83 
VALOR or nte acoso ott cicists kttcts 48-29 
100-00 
Formerly these salts were mixed with washed magnesian lime, and then 
calcined in order to peroxidize the iron. It is found, however (as first 
suggested by Dr. Richardson), that calcination is unnecessary when the solu- 
tion is sufficiently diluted, and when space is provided in the precipitating- 
tank for the bulky precipitate of protoxide of iron which is formed by the 
gradual addition of magnesian lime. This is probably the only chemical 
¢ 
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