1841.] Report on the Soda Soils of the BarramahaL 161 



ness in a gentle heat, by which the extractive and vegetable matters are 

 converted into charcoal, and can then be simply extracted by filtering, and 

 the solution will then crystallize on evaporating to a pellicle. The first 

 crystallization gives a tolerably pure soda, coloured a little by the impuri- 

 ties, but after crystallizing 3 or 4 times the crystals are beautifully white 

 and transparent, and after six crystallizations, the salt is so pure as hardly 

 to give any precipitate with nitrate of silver or nitrate of barytes after 

 supersaturation with nitric acid, denoting thereby the nearly total absence 

 of any muriate or sulphate. 



In England great quantities of carbonate of soda are required in glass 

 making, soap making and dyeing. This was formerly prepared from the 

 Spanish Barilla, which contains, according to Dr. Ure, muriate and sul- 

 phate of soda, lime and abumina, and only at most 24 per cent, of soda. 

 A large quantity was also made from kelp prepared in the Scottish Isles, 

 but this is no longer manufactured, as it has been found that in conse- 

 quence of the cheap price of sulphuric acid, soda can be manufactured by 

 decomposing the muriate of soda (common salt) at a price which remu- 

 nerates the manufacturer. 



In this operation the muriate is first decomposed by heating it in leaden 

 vessels with sulphuric acid, by which the muriatic gas is driven off and 

 which is condensed and allowed to run to waste as of no value, the demand 

 in the arts for muriatic acid being very small. The resulting sulphate of 

 soda is then mixed with charcoal and some lime, and is roasted by a 

 powerful heat in a reverberatory furnace by which it is partly decomposed 

 and formed into sulphurate of soda, which by further heat and stirring is 

 again decomposed and the sulphur volatilized and an impure mixture of 

 carbonate of soda ashes, and charcoal results, which is called in trade 

 \ black balls,' and is an article of commerce. 



This impure product is then further purified by solution in water, fil- 

 tering, and evaporation to dryness without crystallizing, in which state it 

 is called ' Soda Ash' and is used by the glass blowers. 



The salt is still very impure, being mixed with sulphate and muriate of 

 Soda, and does not contain its full equivalent of carbonic acid, being in 

 facta mixture of caustic and carbonate of soda. 



For the makers of plate glass who require a very pure carbonate of soda 

 as a flux, to prevent the chance of the glass being discoloured, the soda 

 ash is mixed with sawdust, and is again fused in a powerful furnace, by 

 which it is fully carbonized and rendered capable of crystallizing. It is 

 then dissolved in water, and is crystallized once for the use of the plate 

 glass makers, and six or seven times for the use of apothecaries. In the 



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