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ON THE CHEMICAL MANUFACTURES OF THE NORTHERN Districts. 705 
manufactory where the waste heat of coke-ovens is utilized in evaporating 
the liquors formed by dissolving rock-salt. Nearly all the salt used in the 
alkali-works is carried by canal to Hull, Goole, or Grimsby, whence it is 
brought to the Tyne at a nominal freight, generally by foreign vessels, that 
take it as ballast when coming to the Tyne for an outward cargo of coals. 
This is the only practical result of the repeal of that portion of the navigation 
laws which prevented foreign ships carrying cargoes coastwise. The annual 
consumption 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, but are omitted here, 
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, 7450 tons; 4, caustic soda, 580 tons. The manu- 
facture is so well understood, that only local peculiarities and recent im- 
provements need be noticed. 
Alkali.—All the Tyne soda-ash is fully carbonated, sawdust being gene- 
rally 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 dissolving, 
settling, evaporating, and calcining, thus producing 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 Lancashire, where a 
hard limestone is used for balling, the percentage of caustic soda is large, 
while the sulphuret exists in small proportion, and is easily oxidized. 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. Consequently the Tyne red liquors 
require a very large quantity of nitrate for their oxidation, and yield so little 
caustic soda that this process has been abandoned in favour of the well- 
known method of boiling a weak solution 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 gene- 
rally 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 fur- 
_ naces 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 
Dunlop. They are so arranged as regards their connexions with one another, 
_ that water runs into the tank which has been most nearly exhausted, and 
liquor of full strength runs off the tank which has been most recently filled. 
The balls are always under the surface of the liquor, and thus escape the 
22 
. partial decomposition and consequent formation of sulphuret, which resulted 
1863. 
