860 SODA, CARBONATE OF 



monocarbonate is dissolved in the mother-liquor, and the passage of carbonic 

 acid through it repeated. By this method a pure bicarbonate is obtained, but the 

 process is costly. 



2. By exposing solid monocarbonate of soda- to an atmosphere of carbonic acid gas. 

 This is known as Smith's process. The crystals of the monocarbonate are placed on 

 shelves, slightly inclined to allow the water to run off, in a large box, containing a 

 perforated false bottom ; carbonic acid is passed into this box under pressure, which 

 latter is scarcely necessary, since the monocarbonate so rapidly absorbs the carbonic 

 acid. When the gas ceases to be absorbed, the salt is taken out and dried by a 

 gentle heat. 



The crystals are found to have lost their water of crystallisation, and to have 

 become opaque and porous, and a bicarbonate, still, however, retaining their original 

 shape. These are ground between stones like flour, care being taken to avoid the 

 evolution of much heat. 



3. Its formation by the action of bicarbonate of ammonia has been already described. 

 Bicarbonate of soda crystallises in rectangular four-sided prisms, which require 



about ten parts of cold water to dissolve them, and if the solution be boiled, it loses 

 carbonic acid, becoming first sesquicarbonate, and ultimately monocarbonate. As 

 usually met with in commerce this salt is a white powder. Its taste is slightly 

 alkaline. It is largely used in medicine, for making seidlitz powders, &c., but the 

 salt generally found in the shops is only a sesquicarbonate, or a mixture of bicar- 

 bonate and sesquicarbonate. 



The latest obtainable returns, show that the materials used on the Tyne in producing 

 soda, and its alkaline manufactures, amount to 1,070,000 tons annually, consisting 

 chiefly of pyrites, salt, chalk, coal, and manganese, the value of which is about 850,000/. 



This outlay produces : 



Tons. 



Soda crystals . 



Alkali 



Bicarbonate of soda 



Sulphate of copper 



Sulphate of soda . 



Bleaching powder 



86,000 Caustic soda 



74,000 Epsom salts 



11,000 Glauber salts 



200 Oil of vitriol 



2,400 Hyposulphite of soda 



27,000 Muriatic acid 



I Chloride of manganese 



Total tons. . 216,330 

 Having an aggregrate value of 1,929,825^. 



The products of the Lancashire chemical works are about the same, the total for all 

 England being : 







Kaw materials ....... 1,700,525 



Manufactured article 3,813,-604 



The remarkable extension of the Alkali trade will be seen by the following state- 

 ment of Exports : 



1858 1859 1860 1861 1862 1863 



cwts. cwts. cwts. cwts. cwts. cwts. 



1,618,289 2,029,761 2,049,582 1,420,327 2,095,249 2,137,015 



1864 1865 1866 1867 1868 1869 



cwts. cwts. cwts. cwts. cwts. cwts. 



2,192,771 2,572,794 2,997,479 3,164,425 3,499,587 3,514,382 



1870 1871 1872 1873 



cwts. cwts. cwts. cwts. 



3,853,393 4,176,667 4,453,068 4,754,425 



In the manufacture of carbonate of soda from common salt, there was always a 

 considerable escape of muriatic acid, which was highly injurious to all surrounding 

 vegetation. This led to the passing of a Bill to regulate this manufacture. 



The Alkali Act of July 28, 1863, is 'An Act for the more effectual Condensation 

 cf Muriatic. Acid Gas in Alkali. Works.' An alkali work is defined by the Act to be 

 1 every work for the manufacture of alkali, sulphate of soda, or sulphate of potash, in 

 which muriatic acid is evolved.' It is required that 'every alkali work shall be 

 carried on in such a manner as to secure the condensation to the satisfaction of the 

 inspector, derived from his ewn examination or from that of a sub-inspector, of not 

 less than 95 per centum of the muriatic acid gas evolved therein.' 



