CARBONATE OF SODA.

Ir 5

Carbonate of soda..Sulphuret of calcium

Caustic lime. io

Carbonate of lime . 5

Foreign matter . 10

3. The next stage is the refining of the crude soda by lixiviation and evapora-tion. 100 parts of raw soda have been found to yield—

Soluble matter.45 m parts.

Soda-waste .cc-? „

1007 „

We shall presently see how this waste is made a source of profit to themanufacturer, but we must now continue to trace the course of the product inwhich our reader is immediately interested.

The lixiviation can be effected by simple filtration, the lumps of crude sodabeing generally placed in tanks with perforated bottoms, but this method entails

Fig. 12.

great labour. The method of lixiviation invented by Mr. James Shanks,of St. Helen’s, is the most economical, as well as the most philosophical.The apparatus is based upon the principle that a short column of a liquid ofsuperior density can be made to balance a higher column of a liquid of aninferior density. A series of tanks are placed together, as shown in the wood-cut, Fig. 13, each tank being about 7 feet 6 inches broad, by 6 feet in depth.

Fig. 13.

At the bottom of the tank is a perforated false sheet-iron bottom, A. From thebottom of each tank to the top is carried a pipe, B, to which, at right angles,is fitted a smaller pipe, 6, communicating with the next tank. Water can besupplied to each tank from the pipes, c; and by means of the taps, c, the lyecan be run off into a trough, d. In the first tank is placed crude soda that