In several former notes and articles in these pages, we have spoken of the severe crisis through which the old established, or "Leblanc," process has now for some years been passing. It is, in fact, pushed well nigh out of the running by the newer process, known as the "ammonia-soda" process, and would have had to give up the battle before now were it not for the fact that one of its by-products, bleaching powder, cannot, so far, be produced at all by the ammonia-soda works. The bleaching powder trade has thus remained in the hands of the workers of the Leblanc process, and its sale has enabled them to cover much of the loss which they are suffering on the manufacture of soda ash and caustic soda.
In brief outline, the old Leblanc process consists in the following operations: Salt is decomposed and boiled down with sulphuric acid. Sulphate of sodium is formed, and a large amount of hydrochloric acid is given off. This is condensed, and is utilized in the manufacture of the bleaching powder mentioned above. The sulphate of sodium, known as "salt cake," is mixed with certain proportions of small coal and limestone, and subjected to a further treatment in a furnace, by which a set of reactions take place, causing the conversion of the sulphate of sodium of the "salt cake" into carbonate of sodium, a quantity of sulphide of calcium being produced at the same time. The mass resulting from this process is known as "black ash." It is extracted with water, which dissolves out the carbonate of sodium, which is sold as such or worked into "caustic" soda, as may be required. The insoluble residue is the "alkali waste," which forms the vast piles, so hideous to look at and so dreadful to smell, which surround our large alkali works.
The sulphuric acid required for the conversion of the salt into "salt cake" is made by the alkali manufacturer himself, this manufacture necessitating a large plant of "lead chambers" and accessories, and keeping up an immense trade in pyrites from Spain and Portugal. The development of the alkali trade in this country has been something colossal, and the interests involved in it and connected with it are so great that anything affecting it may safely be said to be of truly national importance, quite apart from what technical interest it may possess.
The "ammonia-soda" process, which has played such havoc with the old style of manufacture, proceeds on totally different lines. Briefly stated, it depends on the fact that if a solution of salt in water is mixed with bicarbonate of ammonium, under proper conditions, a reaction takes place by which the salt, or chloride of sodium, is converted at once into bicarbonate of sodium, the bicarbonate of ammonium being at the same time converted into chloride of ammonium.
The bicarbonate of sodium settles out at once as insoluble crystals, easily removed, marketable at once as such, or easily converted into simple carbonate of sodium, and further into caustic soda, as in the ordinary "old" process. The residual chloride of ammonium is decomposed by distillation with lime, giving ammonia for reconversion into bicarbonate of ammonium, and chloride of calcium, which is a waste product.
The maker of "ammonia" soda works direct on the brine, as pumped from the salt fields. His plant is simpler and less costly, and he arrives at his first marketable product much more rapidly and with very much lower working costs than the maker of Leblanc soda, in spite of all the great mechanical improvements which have of late years been introduced into the old process, and which have cheapened its work.
The original patents on the use of ammonium bicarbonate have, we understand, long since expired. But the working details of the process and much of the most successful apparatus have undergone great development and improvement during late years, all the important points being covered by patents still in force, and mainly, if not wholly, in the hands of the one large firm which is now carrying on the manufacture in this country, and is controlling the market.
The one weak spot of the ammonia-soda process, as we mentioned before, is its inability to supply hydrochloric acid or chlorine, and so allow of making bleaching powder. Time after time it has been announced positively that the problem was solved, that the ammonia-soda makers had devised a method of producing hydrochloric acid or chlorine, or both, without the use of sulphuric acid. But the announcements have so far proved baseless, and at present the Leblanc makers are getting incredulous, and do not much excite themselves over new statements of the kind, though they know that if once their rivals had this weapon in their hands the battle would be over and the Leblanc process doomed to rapid extinction.
Such is at present the state of the struggle in this great industry, and the above outline sketch of the two processes is designed to give some idea of the conditions to such of our readers as may not have any special knowledge of these manufactures.
At the present moment great interest is being taken in a new process, about to be put to work on a large scale, which is designed to take up the cudgels against the ammonia process and enable the Leblanc makers to continue the fight on something more like equal terms.
We allude to the process proposed and patented by Messrs. Parnell & Simpson, and about to be worked by the "Lancashire Alkali and Sulphur Company," at Widnes. We recently had the opportunity of inspecting fully the plant erected, and of having the method of procedure explained to us. We look upon the new process as such a spirited attempt to turn the tide of a long and losing battle, and as so very interesting on its own merits, that an account of it in these pages will be thoroughly in place.
The main idea of the process is to combine the "Leblanc" and the "ammonia-soda" manufacture. But in place of using caustic lime to decompose the ammonium chloride and get back the ammonia, the "alkali waste" spoken of above is employed, it being found that not only is the ammonia driven off, but that also the sulphur in the "waste" is obtained in a form allowing of its easy utilization, it and the ammonia combining to form ammonium sulphide, which passes over in gaseous form from the decomposing apparatus. This ammonium sulphide is, as we shall see, quite as available for the working of the ammonia-soda manufacture as pure and simple ammonia, and all the sulphur can be obtained from it.