Scientific American Supplement, No. 717, September 28, 1889, by Various, is part of the HackerNoon Books Series. You can jump to any chapter in this book here. ALKALI MANUFACTORIES.
ALKALI MANUFACTORIES.
When the alkali, etc., Works Regulation Act was passed in 1881, it was supposed that the result would be that the atmosphere in the districts where such works are situated would be considerably improved, and, consequently, that vegetation would have a better chance in the struggle for existence, and the sanitary conditions of human dwellings would be advanced. In all these respects the act has been a success. But perhaps the most notable result is the effect which the act and those which have preceded it have had upon the manufactures which they control.
This was not anticipated by manufacturers, but now one of the principal of them (Mr. A. M. Chance) has stated that "Government inspection has not only led to material improvement in the general management of chemical works, but it has also been in reality a distinct benefit to, rather than a tax upon, the owners of such works."
This expression of opinion is substantiated by the chief inspector under the act, whose report for last year has recently been laid before the local government board.
There are 1,057 works in the United Kingdom which are visited by the inspectors, and in only two of these during 1888 did the neglect to carry out the inspectors' warnings become so flagrant as to call for legal interference; viz., in the case of Thomas Farmer & Co. (limited), Victoria Docks, E., who were fined 20l. and costs for failing to use the "best practicable means" for preventing the escape of acid gas from manure plant; and in the case of Joseph Fison & Co., Bramford, who were fined 50l. and costs for excessive escape of acid gas from sulphuric acid plant. There were seven other cases, but these were simply for failure to register under the act.
It is very evident, therefore, that from a public point of view the act is splendidly successful, and from the practical or scientific side it is no less satisfactory.
Of the total number of chemical works (1,057) 866 are registered in England, 131 in Scotland, and 44 in Ireland—a decrease in the case of Scotland of 8, and in Ireland of 2 from the previous year, while England has increased by 1. This must not, however, be taken as a sign of diminished production, because there is a tendency for the larger works to increase in size and for the smaller ones to close their operations. The principal nuisances which the inspectors have to prevent are the escape of hydrochloric acid gas from alkali works and of sulphurous gas from vitriol and manure works.
The alkali act forbids the manufacturer to allow the escape of more than 5 per cent. of the hydrochloric acid which he produces, or that that acid must not exist to a greater extent than 0.2 grain in 1 cubic foot of air, steam, or chimney gas which accompanies. The inspectors' figures for last year show that the percentage of the acid which escaped amounted to only 1.96 of the total produced, which is equal to 0.089 grain per cubic foot, and much below the figures for previous years. The figures in regard to sulphurous gas are equally satisfactory. The act allows 4 grains of sulphuric anhydride (SO3) per cubic foot to escape into the air, and last year's average was only 0.737 grain, or less than a fifth of the limit.
Of course it is now the aim of the Leblanc alkali manufacturers to reduce the escape of hydrochloric acid to the lowest possible amount, as their profits depend solely upon the sale of chlorine products, soda products being sold at a loss. In this connection it is interesting to note that the amount of common salt manufactured in the United Kingdom in 1888 was 2,039,867 tons, and of this nearly 600,000 tons were taken by Leblanc soda makers, and over 200,000 tons by the ammonia-soda makers. The figures are very largely in excess of previous years, and indicate a gratifying growth in trade.
The salt used in the Leblanc process yields the hydrochloric acid, and that in the ammonia-soda method none, so that we may put down the theoretical production of acid as 380,000 tons, 7,600 tons of which was allowed to escape.
What was a mere trace in the chimney gases amounts, therefore, to a good round figure at the end of a year, and if it were converted into bleaching powder it would be worth nearly 150,000l. These figures are, it should be understood, based on theory, but they serve to show to what importance a gas has now reached which twenty-five years ago was a perfect incubus to the manufacturers, and wrought desolation in the country sides miles and miles around the producing works. There has long been an expectation that the ammonia-soda makers would add the manufacture of bleaching powder to their process, but they appear to be as far as ever from that result, and meanwhile the Leblanc makers are honestly striving to utilize every atom of the valuable material which they handle. Hence the eagerness to recover the sulphur from tank waste by one or other of the few workable processes which have been proposed.
This waste contains from 11 to 15 per cent. of sulphur, and when it is stated that the total amount of tank waste produced yearly is about 750,000 tons, containing about 100,000 tons of sulphur, it will be seen how large is the reward held out to the successful manipulator. Moreover, the value of the sulphur that might possibly be saved is not the only prize held out to those who can successfully deal with the waste, for this material is not only thrown away as useless, but much expense is incurred in the throwing.
In Lancashire and in other inland districts land must be found on which to deposit it, and the act of depositing is costly, for unless it is beaten together so as to exclude the air, an intolerable nuisance arises from it. The cost of haulage and deposit on land varies, according to the district, from 1s. to 1s. 6d. a ton. In Widnes it is about 1s.
In the Newcastle district the practice is to carry this material out to sea at a cost of about 4d. a ton.
Mr. Chance's process for the recovery of sulphur from the waste signalizes the centenary of the Leblanc process; Parnell and Simpson are following in his wake, and lately Mr. F. Gossage, of Widnes, has been working on a process for the production of alkali, which enables him to save the sulphur of the sulphuric acid. In his process a mixture of 70 parts Leblanc salt cake (sulphate of soda) and 30 parts common salt is mixed with coal and heated in a furnace, and so reduced to sulphide of sodium. The resulting "ash" is then dissolved in water and exposed to the action of carbonic acid, when sulphureted hydrogen is given off, to be dealt with as in Mr. Chance's sulphur process, while bicarbonate of soda is formed and separates by precipitation from the solution of undecomposed common salt.
Ere long it is expected this new method will be in active operation in some Leblanc works, the plant of which will, in all probability, be utilized. It has these great advantages: The absence of lime, the recovery of the sulphur used in the first instance and the consequent absence of the objectionable tank waste. Thus a bright promise is held out that the days of alkali waste are numbered, and that the air in certain parts of Lancashire will be more balmy than it has been in the memory of the oldest inhabitant.—Chemist and Druggist.
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