Sn EE MD 
ON THE CHEMICAL MANUFACTURES OF THE NORTHERN Districts, 711 
manufacture of the district, with the exception of prussiate of potash, which 
has greatly fallen off in extent, a more rational system of medicine having 
diminished the use of purgatives, and reduced the demand for Epsom salts to 
about one-third of what it was twenty years ago. The annual production is 
still 1500 tons, two-thirds of which are made from the rough salts. 
Carbonate of Magnesia.—This compound has long been produced in this 
district, where it was formerly, and is still to a limited extent, manufactured 
from the mother liquors of the salt-pans known as Bittern, to which carbonate 
of soda is added to precipitate the magnesia in the form of carbonate. This 
old plan has been largely superseded by the elegant process of the late Mr. 
H. L. Pattinson, which consists in submitting calcined magnesian limestone 
to the action of carbonic acid and water, under pressure. The magnesia dis- 
solves out as bicarbonate of magnesia, from which the neutral carbonate of 
magnesia is precipitated by the application of heat. The quantity manufac- 
tured is said to be about 250 tons per annum. 
Superphosphate of Lime.—The manufacture of this article was commenced 
at Blaydon in 1844, by Dr. Richardson, soon after the publication of Liebig’s 
celebrated report on agricultural chemistry. Various materials are employed 
as the source of phosphate of lime, viz. bones, bone-ashes from South America, 
exhausted animal charcoal from the sugar-refineries, coprolites from Suffolk 
and Cambridgeshire, phosphorite from Spain, Sombrero guano, &c. Improve- 
ments have been introduced in the manner of mixing the acid with these 
substances, in drying, and in the riddling of the superphosphate. The quantity 
produced amounts to between 15,000 and 16,000 tons per annum. 
Pearl-hardener.—This article has only recently been manufactured here, 
and its introduction is due to Dr. Jullion, who has applied it to the hardening 
of paper. It is produced by precipitating hydrated sulphate of lime from a 
perfectly pure solution of chloride of calcium by means of sulphuric acid, 
Great care is taken in its preparation, and it is being generally introduced 
among the manufacturers of paper. The quantity made is said to be about 
2000 tons per annum. 
Sulphate of Iron.—The first manufactory for the production of green 
copperas in England was founded about the year 1579, when one Matthew 
Falconar, a Brabanter, “did try and draw very good brimstone and copperas 
out of certain stones, gathered in great plenty on the shore, near unto 
Minster, in the Isle of Sheppey.” Mr. Thomas Delaval commenced to 
manufacture copperas at Hartley about the year 1748, but he subsequently 
sold the manufactory to his brother, Lord Delaval, and by an Act of Parlia- 
ment, 11th of George III., 1771, power was given to Sir Francis Blake 
Delaval to grant to Sir John Hussey Delaval, in fee simple, all the copperas- 
works then and there existing; which may enable us to form some idea of 
the importance then attached to this manufacture. The late Mr. Barnes and 
Alderman Forster erected the first copperas-works on the Tyne, at Walker, 
in 1798, which are still in operation. The quantity at present manufac- 
tured is about 2000 tons per annum, and the process is still the same; but 
Mr. Thomas Barnes has applied the refuse crystals to a novel purpose. This 
refuse was, and is, generally thrown away; but Mr. Barnes uses it as a 
manure on his farm, on the thin soil which lies on the magnesian limestone. 
He finds that the depth of the soil is gradually increasing by the disintegra- 
tion of the rock, and that the more he uses, the more satisfactory are the 
results. The beneficial effect of the copperas is doubtless partly due to the 
natural decomposition of the carbonate of lime with the sulphate of iron, and 
partly to the action of the peroxide of iron on the organic matter of the soil. 
