CHEMICAL MANUFACTURES ON THE TYNE. 131 



sition of common salt in the district is 90,000 tons, requiring 73,800 

 tons of sulphuric acid, and producing 100,000 tons of dry sulphate of 

 soda. The whole of this quantity is used in the manufacture of alkali. 

 A few hundred tons are consumed in the glass manufacture, hut are left 

 out of this account, as no account has been taken of the sulphate of 

 soda made from the nitrate of soda in the sulphuric acid process. The 

 alkali is produced in the four forms of — 1. Alkali or soda ash, 43,500 

 tons. 2. Crystals of soda, 51,300 tons. 3. Bicarbonate of soda, 7,450 

 tons. 4. Caustic soda, 580 tons. The manufacture is so well understood 

 that only local peculiarities and recent improvements need be noted. 



Alkali. — All the Tyne soda ash is fully carbonated, sawdust being 

 generally used in the furnace for this purpose, so that it contains merely 

 a trace of hydrate of soda. The greater part of it is also refined by dis- 

 solving, settling, evaporating, and calcining ; producing thus an article 

 of great whiteness and purity. 



Caustic Soda. — This manufacture is as yet quite in its infancy in 

 this district. In Lancashire very large quantities are made from the 

 " red liquors " which drain from the soda salts. These liquors always 

 contain caustic soda, sulphuret of sodium, and common salt. In Lan- 

 cashire, where a hard limestone is used for balling, the percentage of 

 caustic soda is large, while the sulphuret exists in small proportion, and 

 it is easily oxidised. It would seem that the London chalk which is 

 used here produces a lime, chemically much less energetic, forming less 

 caustic soda, and holding sulphur more loosely in combination. Con- 

 sequently, the Tyne red liquors require a very large quantity of nitrate 

 for their oxidation, and yield so little caustic that this process has been 

 abandoned in favour of the well-known method of boiling a weak solu- 

 tion of alkali with lime. This has the advantage, however, of producing 

 a richer and very pure article, sometimes as strong as 74 per cent. 



The improvements (besides such as have been already noticed) which 

 have been introduced into the alkali trade since the last meeting of the 

 British Association in Newcastle, may be divided into those which have 

 been generally adopted, and the special improvements of individual 

 manufacturers. 1st. Economy of labour has been attained by using 

 larger furnaces, in which a workman can manipulate a larger charge 

 with less toil, and by various other appliances purely mechanical. 2nd. 

 Economy of fuel has been largely attained by the application of the 

 waste heat and flame from the ball furnaces to the surface evaporation 

 of the tank or black ash liquor. Formerly this was evaporated in 

 hemispherical cast-iron pans, each with a fire below. 3rd. Economy of 

 water and fuel by the adoption of the circulating tanks for lixiviating 

 balls, first introduced at Glasgow by the late Mr. Charles Tennant Dun- 

 lop. They are so arranged as regards their connections with one 

 another that water runs into the tank which has been most nearly ex- 

 hausted, and liquor of full strength runs off the tank which has been 

 most recently filled. The balls are always under the surface of the 



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