ON THE PREPARATION OF SODA AND CHLORINE. 45 



the whole of the chlorine contained in the common salt is liber- 

 ated in the gaseous state. By means of the exhausting apparatus, 

 the chlorine, together with the nitrogen of the atmosphere, which 

 is not absorbed by the mixture, is drawn, first through a 

 layer of coke kept moist by water trickling over it, and then 

 through lime slaked to a dry powder, somewhat in the same man- 

 ner as common illuminating gas is passed through the dry lime 

 purifier. The gases are freed by the water from any muriatic 

 acid they may contain, and the chlorine is then quickly absorbed 

 by the lime, and bleaching powder, or chloride of lime obtained. 

 In the furnace there remains a residue consisting of about 427 

 parts of sulphate of soda and 312 parts peroxide of iron, which is 

 withdrawn and treated in the manner about to be described. This 

 production of chlorine and bleaching powder, and of a residue of 

 sulphate of soda and peroxide of iron, may be called the first 

 part of the new process. 



This mixture of sulphate of soda and peroxide of iron is next 

 mixed with 144 parts of powdered coal or charcoal, and is then 

 introduced into a reverberatory furnace, the hearth of which has 

 been previously prepared in the following manner : 100 parts of 

 ground quicklime are mixed with 16 parts of basic slag, such as 

 commonly produced in copper-smelting works, or of any other 

 slag or glass not too difficult of fusion. This mixture is beaten 

 into the bottom of the furnace, when in a dry state, the depression 

 is then scooped out in it, and the tap-hole formed through it at 

 the bottom, as is customary in preparing the hearths of furnaces 

 intended for smelting. The furnace is now gradually heated up, 

 and a strong heat continued, until the materials of the hearth have 

 slightly caked together. As soon as this takes place a mixture of 

 100 parts of sulphate of soda and 25 parts of powdered coal or 

 charcoal is introduced. This soon fuses and is totally absorbed 

 by the hearth. More of the same mixture is then introduced, and 

 this continued until no more of the resulting sulphuret of sodium 

 is absorbed by the hearth. The furnace is then kept at a red heat, 

 and is ready to receive the mixture of sulphate of soda, peroxide 

 of iron and chareoal or coal already referred to. As soon as this 

 mixture has entered into quiet fusion it is drawn off by the tap- 

 hole into iron moulds or wheel-barrows, in which it solidifies 



t 



in large blocks. It is totally without corrosive action on the 

 hearth ; and an almost unlimited number of charges may be smelt- 

 ed down, without the hearth being at all affected. This on the 



