PROGRESS OF CHEMISTRY IN SOUTH LANCASHIRE. 113 



In the preparation of solid caustic soda advantage is taken of the facts, that 

 in all the black-ash liquors nearly one-third of the total alkali is present 

 as the hydrate, and that on concentrating these liquors by boiling, the whole 

 of the carbonate, and the greater part of the chloride, sulphate, and other 

 neutral salts separate, and may be removed by mechanical means, leaving 

 in solution the caustic alkali with a small quantity of sulphides and cyanides 

 <vhich are oxidized by nitrate of soda, as afterwards described. Sometimes, 

 however, it is found convenient to caustitize with linie the whole of the 

 black-ash liquor before evaporation : the caustic alkali must then be prepared 

 in a dilute solution ; otherwise, as is well known, a complete decomposition 

 does not occur. In order to utilize the heat wasted by the necessary evapo- 

 ration of the lye, Mr. Dale has patented a plan for boiling down the caustic 

 liquors iu closed iron boilers, employing the steam for motive power or for 

 heating purposes. . Mr. Dale finds that the liquors may be thus concentrated 

 to sp. gr. ISO without in any way injuring the boilers. When the lye has 

 obtained the above strength, it is concentrated in open iron pans, and nitrate 

 of soda is added to oxidize the sulphides and sulphites, large quantities of 

 ammonia being evolved. As soon as the greater portion of the uncombined 

 water has gone off, and the mass begins to undergo igneous fusion, the 

 cyanides are decomposed by the nitrate — nitrogen and oxygen gases being 

 liberated, and the carbon of the cyanogen appearing as a crust of finely 

 divided graphite. This interesting fact of the production of graphite by 

 decomposition, probably, of the cyanides, was first observed by Dr. Pauli of 

 the Union Alkali-works of St. Helens. The caustic soda thus prepared is 

 often perfectly white, although generally of a greenish colour from traces of 

 manganese; it contains neither iron noralumina, the former being precipitated 

 as an insoluble anhydrous peroxide, and the latter separating out as a crystal- 

 line alkaline silicate of alumina. 



In concentrating the strong lye, the manufacturers were much troubled by 

 the continual boiling over of the fusing mass, but this has been remedied by 

 an ingenious application of the "Geyser" principle, also used in the kiers 

 employed in bleaching cotton goods, which we saw in operation at Messrs. 

 Gaskell and Deacon's Works at Widnes. At the bottom of the round pan 

 in which the evaporation is conducted is placed a conical pipe of sheet iron, 

 open at both ends, and reaching about an inch above the level of the fusing 

 mass. This tube does not rest close to the bottom of the pan, openings 

 being left for the entrance of the liquid. In contact with the heated iron, 

 steam is formed at the bottom of the tube, and the liquid is thus forced out 

 at the top of the tube, preventing altogether any violent ebullition occurring 

 in the other part of the pan, and consequently effectually stopping the boiling 

 over of the fused mass. 



The proposition recently made by Kuhlmann for the employment of the 

 alkali-waste as a cement is not new, Mr. Deacon of Widnes having used this 

 waste material for making floors twelve years ago. 



The investigations of Mr. Gossage on the constitution of black ash have 

 been the base of a very important branch of that manufacture. This gentle- 

 man, so long ago as 1838, expressed his doubts as to the correctness of the 

 view taken by Dumas and other chemists concerning the composition of the 

 black ash, namely, that the separation of the soluble carbonate of soda from 

 the compounds of sulphur and lime by treatment with water depends upon 

 the formation of an insoluble oxysulphide of calcium. Mr. Gossage showed 

 that in all the liquors obtained by dissolving the black ash nearly one-third of 

 the total quantity of alkali is present as caustic soda, and that this closely 

 corresponds to the excess of caustic lime practically employed, whereas in 



186J. J 



