180 CHEMICAL MANUFACTURES ON THE TYNE. 



The sulphate of ammonia is manufactured direct from the gas water, 

 in the following manner : — A large cylindrical boiler is filled two-thirds 

 full with the gas liquor, and gently boiled. The gaseous products and 

 steam are conducted into a mother liquor, from a previous operation, 

 which is kept slightly acid. When no more ammonia comes over, a 

 quantity of milk of lime is added to the boiler and a strong heat ap- 

 plied, until the colouring matters cease to be disengaged. The gaseous 

 products are collected as before, and the colouring matters are skimmed 

 off the surface of the liquor. The boiling is then moderated, and during 

 the whole operation, a stream of acid is supplied to the !cistern. The 

 sulphate of ammonia salts out, and is fished up into baskets to drain, 

 when it is ready for the market. 



Cement.— The manufacture of this material, on a large scale in this 

 district, is of comparatively recent origin. A small quantity of cement 

 has long been made on the Yorkshire coast, near Whitby, where a 

 peculiar mineral is found in the alum shale, called the " Cement Stone." 

 This mineral has been analysed by Dr. Richardson, who found it to 

 contain — 



Clay insoluble in Acids 18*41 



Consisting of Silica 



,, of Alumina 



Alumina soluble in Acids 



Oxide of Iron 



Lime 



Magnesia 



Soda and Potash ... 



Organic Matter 



Carbonic Acid and Water 



9977 



About 20 cwt. of this mineral is found in every 60 tons of shale, 

 and the greater proportion is sent to Hull, where it is manufactured 

 into a cement, sold under the name of Mulgrave Cement. 



The mineral is burnt in small open kilns, and afterwards ground to 

 a fine powder. 



The production of cement on a large manufacturing scale, dates from 

 the establishment of the works of Messrs. T. C. Johnson and Co., in 

 1856. This firm manufactures Portland Cement, Roman Cement, 

 Keene's Marble Cement, and Plaster of Paris ; and they have recently 

 introduced improved machinery for the more perfect levigation of the 

 raw materials, by which the subsequent chemical action is much 

 facilitated. 



Portland cement is very extensively used in this country, in France 

 and Germany, for dock works, basins, fortifications, and for fronting 

 houses in imitation of stone. It is also used for coating the inside of all 



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6-89 





0-54 





37*68 





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traces 





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