SODA PROCESS. 



471 



use, but is now superseded by sulphate of magnesia. It is still, 

 however, combined with the tartrate of potash and soda, in 

 Seidlitz powders. 



PREPARATION OF CARBONATE OF SODA FROM THE SULPHATE. 



The sulphate of soda is chiefly formed, as a step in the pro- 

 cess of preparing soda from common salt. The same manufac- 

 ture requires large quantities of sulphuric acid, not less than 

 1 2,000 tons of sulphur being annually converted into that acid 

 in England ; and by means of the acid, 50,001 ) tons of salt con- 

 verted into sulphate of soda. From the last, upwards of 50,000 

 tons of soda ash, and 20,000 tons of crystallized carbonate of 

 soda were manufactured, in 1838 j and the manufacture is greatly 

 on the increase.* 



A reverberatory furnace is employed in soda-making and 

 various other chemical manufactures, to afford the means of ex- 

 posing a considerable quantity of materials to a strong heat, 

 of which a perpendicular and a horizontal section are given in 



FIG. 48. 



figure 48. It consists of a fire- 

 place a, in which the fuel is burned, 

 of which b is the ash-pit, with a 

 horizontal flue expanded into a 

 small chamber or oven d d, which 

 is raised to a strong red heat, by 

 the reverberation on its walls of 

 the flame, or heated air from the 

 fire, on its passage to the chimney. 

 The matters to be heated are placed 

 upon the floor of this chamber. It 

 has an opening i in the side, for 

 the introduction of materials, and 

 another opening g at the end most 



oxygen, or with two. The relation between the two salts is thus brought 

 out : 



Hypermanganate of barytes is, .... Ba O + Mn 2 O ? 



Or, on the binary theory of salts, . . . . Ba + Mn 2 O 8 . 



Two atoms of sulphate of soda, on the same theory, are Na 2 + S 2 O 8 ; 



Or, 2Na being really " So," " So" + S 2 O 8 . 



It will be observed that, as represented by the second and fourth formulae, 

 hypermanganate of barytes and sulphate of soda have a similar atomic con- 

 stitution ; they should therefore be isoraorphous. (Records of General Sci- 

 ence, Vol. IV., page 45.) 



* Information supplied by Mr. Muspratt of Liverpool. 



