112 REPORT— 1861. 



the great drawback of Leblanc's original method ; but none have been as yet 

 found to be practicallysuccessful, if, indeed, we except a process used by the St. 

 Helens Patent Alkali Company, in which the bisulphide of iron (iron pyrites), 

 being roasted in a reverberatory furnace with common salt, yields volatile 

 sesquicliloride of iron, salt-cake, and peroxide of iron, which are sepax'ated 

 by lixiviation. A process, theoretically most promising, has been proposed by 

 Mr. Gossage, to whom the alkali-trade owes so much, by which all loss of 

 sulphur is avoided ; but even this plan has not yet been successfully worked. 

 It depends ujjon the following facts : (1) that moist carbonic acid decomposes 

 sulphide of sodium, forming carbonate of soda and sulphuretted hydrogen ; 

 and (2) that dry peroxide of iron is reduced by sulphuretted hydrogen — free 

 sulphur, water, and protoxide of iron being formed, — the latter part of the 

 process having been patented by Mr. Thomas Spencer in 1859. The salt- 

 cake, made in the usual way, is in this process reduced by coal, and the fused 

 sulphide allowed to flow through a tower filled with heated coke, in which it 

 meets a current of moist carbonic acid ; the carbonate of soda runs out at 

 the bottom of the tower, whilst the sulphuretted hydrogen and carbonic acid 

 gases pass upwards through a tower tilled with peroxide of iron in porous 

 masses. The sulphur is there deposited upon the oxide of iron, and the mass 

 only needs burning in the ordinary pyrites-kilns to yield sulphurous acid 

 again. The numerous plans proposed for regaining the sulphur from the 

 alkali-waste have also all proved abortive ; nor indeed is this to be wondered 

 at when we consider the mechanical difficulties of dealing with a mass of 

 material amounting in some works to 600 tons weekly, and when we like- 

 wise remember that the waste contains only from 15 to 20 per cent, of sul- 

 phur, which, if it could all be easily extracted, Avould only make the mass 

 worth about 15*. per ton. 



The improvements of detail effected in the soda- manufacture since the 

 year 1851 have mainly been the following: — 



(!) Greater attention to economical working in all the branches than was 

 formerly given, especially in the burning of pyrites, and in the evaporation 

 of the black-ash liquors, which is now wholly effected by the waste heat 

 from the black-ash furnaces. The arrangement for the evaporation of the 

 black-ash liquors by means of the spent heat of the black-ash furnaces was 

 proposed by Mr. Gamble of St. Helens, and by him liberally presented to 

 his co-manufacturers. 



(2) The process of lixiviation of the black ash is more completely accom- 

 plished than formerly by the employment of the very ingenious and simple 

 arrangement originally proposed by Mr. Shanks, and by him given to the 

 soda-trade. According to Mr. Shanks's method, all pumping of the liquors 

 or handling of the black ash is avoided, a much more perfect abstraction of 

 the soluble constituents is gained, and a great saving in expense of evapora- 

 tion is effected. 



(3) In some works the black ash is now made by machinery, under a 

 patent granted to Messrs. Elliot and Russell in 1853, and more recently 

 improved by Messrs. Stevenson and Williamson of the Yarrow Chemical 

 Works, Newcastle. In this method the mixture of salt-cake, coal, and lime- 

 stone is introduced into revolving iron cylinders, lined with firebricks, and 

 heated by a furnace, so that thus the process of manual stirring is avoided. 



(i) The soda-ash is now in many alkali-works packed into casks by 

 machinery. 



Since the year 1851 an entirely new branch of the manufacture has been 

 introduced by the preparation of solid caustic soda, an article now largely 

 exported to America and other localities, to which carriage is expensive. 



