176 CHEMICAL MANUFACTURES ON THE TYNE. 



from which Prussiate of potash was afterwards manufactured. This salt 

 was not known in commerce in a crystallised form, however, till about 

 the year 1825, when the price was 5s. per pound. The price has now fallen 

 to ll^d. Mr. Bramwell has introduced various improvements in the 

 manufacture of this salt, employing close pots, in which the fused ma- 

 terials are worked by machinery, and substituting sulphate of potash 

 for the more expensive potashes ; but notwithstanding the application 

 of every chemical and mechanical appliance, and the low prices at which 

 the prussiate of potash is sold, the demand has fallen off, and at present 

 only two .tons of yellow prussiate, and three-quarters of aton of red prus- 

 siate are manufactured weekly. The decline in this trade has arisen 

 partly from the American civil war, and partly from the introduction 

 of the aniline colours. The celebrated attempt in 1844 to produce 

 cyanogen from the nitrogen of the air, was made at these works, and 

 although the efforts of Mr. Bramwell and his friends were perfectly suc- 

 cessful in a chemical point of view, these gentlemen were induced to 

 abandon the process as a manufacturing operation. 



Alum. — The first alum works established in England were erected 

 at Guisbro' in 1460, by Sir Thomas Challoner, who brought over a work- 

 man from France to carry out the then secret process, the monopoly of 

 tliis trade being in the hands of the Pope. The works were subsequently 

 decreed to be a royal mine, and passed into the possession of the crown. 

 They were afterwards farmed to Sir Paul Pindar at a rental of 15,000?. 

 per annum. He employed about 800 persons, and made large profits, 

 his monopoly enabling him to keep up the price to 261. per ton. The 

 Long Parliament restored the mines to the original owners, and at the 

 Restoration not less than five manufactories were in operation. The pro- 

 cess is well known, but potash alum (formerly the only alum made) is 

 now only produced at the Loftus Works, all the other manufacturers em- 

 ploying the cheaper sulphate of ammonia. From the mother liquors large 

 quantities of an impure sulphate of magnesia are obtained, which are partly 

 refined, and partly consumed as a manure, mixed 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, 4,000 tons ; rough 

 Epsoms, 1,800 tons. Some improvements in the details have been intro- 

 duced to economise 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 Guisbro' Alum Com- 

 pany have introduced an aluminous cake, containing sulphate of mag- 

 nesia, which has been found to answer very well in dyeing certain 

 colours, as browns, blacks, &c, and in the manufacture of all kinds of 

 coarse paper. 



Epsom Salts. — The abundant supply of Dolomite 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 



