4. The fact that coarsely crystallized salt can be produced at the same time as the finest table salt.
5. That the proportion of the different grades of salt can be varied at will, as well as maintained constantly, to suit the varying requirements of the market.
6. The automatic and continuous removal of the salt as fast as it is precipitated from the brine.
The essential features of the Hodgkinson plant consist of (a) a mechanically-stoked furnace for the production of heat; (b) a primary closed evaporating pan, 30 ft. in diameter; (c) two secondary circular pans, 25 ft. in diameter; (d) four open rectangular pans, 60 ft. by 25 ft.; (e) a series of folded steam-jacketed pipes for heating the inflowing brine by the waste steam; and (f) a condensing arrangement to produce a partial vacuum in the closed pans.
The Hodgkinson furnace is not placed under the pan, as in the old system, but in front of the plant, and the heated gases pass under the primary pan, where the temperature ranges between 1,800 and 2,000°F. In this primary pan is made a finer and better salt than can be manufactured by any other system in the world. Moreover, by means of the mechanically-stoked furnace, and the consequent uniform high temperature, it is possible, for the first time, to control the character of the salt produced. Where the temperature varies, as in the open-pan system, crystals of varying shapes and sizes are produced, and this mixed salt must be ground to make it suitable for table purposes. Where steam heat is employed, as in the vacuum process, the temperature is not high enough to make crystals of the smallest size. By the Hodgkinson system the primary pan produces a precipitation which requires no grinding, which flows in a cascade of salt from the pan, and can be delivered to the consumer without having come into contact with the hand of man in the whole course of the operation.
The heated gases, having passed under the primary pan, are then divided and sent under the two secondary pans, and from thence they pass under the open rectangular pans, the gases being distributed by the broken columns of brickwork on which the pans stand. The temperature of the gases passing under the open pans commences at about 600° F., and gradually decreases to about 200° F. under the farthest pans. By the automatic regulation of the temperature, the waste gases are utilized to produce salts of the various degrees of coarseness required for the dairy, the stock-yard, and fishery purposes. In the two secondary closed pans, finely divided table salt is also produced, but it is possible, by opening the manhole traps in the covers, to increase the size of the crystal and make dairy salt in these pans. The coarser crystals and flake salts are made in the open pans in which the crystallization is at the lowest rate. The grain of the salt can be altered at will. In order to meet any change in the market requirements, coarser salt can be produced at a moment’s notice in the secondary pans. One very marked superiority of the whole system over all other processes is seen in the fact that a change in the type of salt produced can be immediately effected, and a constant and uniform output of any combination of products can be absolutely guaranteed.
The improvements which the Hodgkinson plant has effected in the open-pan system are: the increased production of from 2 to 7 tons of salt from the combustion of 1 ton of coal, the production of the finest table salt without grinding, and of every grade of salt from the flour-fine table to the coarsest fishery salt, in one and the same operation, and the saving of time that is required in all other processes for scraping and cleaning the pans. Its superiority over the Vacuum system lies in the facts that its initial cost is about £4,000, as against anything from £26,000 to £100,000; that the majority of the work being automatic, the expense of specially trained, skilled labour is dispensed with; that it is operated for 24 hours a day as against 20; requires no grinding process in the manufacture of table salt; and produces every grade of salt simultaneously. Sir Thomas Holland, while studying the Hodgkinson process in operation, is said to have exclaimed: “This is not an improvement, it is a revolution”; and in his subsequent report upon the process, he has declared that it “has an enormous advantage over any known process for the production of salt.”
CHAPTER VIII
THE SALT MARKET
Although no purpose would be served by dealing in detail with other of the many schemes that have been elaborated in the past three hundred years for the improvement of brine salt manufacture, the complete list of patents that have been taken out for the purpose constitutes a record of almost unrelieved failure which would occupy many pages. It has always been obvious to every intelligent investigator outside the little circle of salt proprietors, that the open-pan process was a survival of the dark ages, but the principle governing the precipitation of salt from brine is so simple that the equal difficulty presented itself to the practical salt-men, of either effecting further simplification or of securing further economies by the elaboration of the process. Individuals in every generation recognized that the methods of mediaevalism cried aloud for revision, but the salt trade resolutely and consistently set their faces, and their hands, against every suggested innovation. The salt-men were the avowed enemies of Thomas Lowndes, they drove Chrysel back to Saxony, they loaded Furnival with misfortune and landed him in gaol. In 1890, an official of the Salt Union reflected with grim complaisance that, although no trade had had more patents applied to it than the salt trade, no trade could show so large a percentage of failures in the matter of reformed methods, and since all the companies that had brought forward new plants and processes in competition with the Salt Union had come short of success, he piously concluded that the system which had survived the trial of generations must be the fittest.
The opposition of the salt trade to the introduction of new methods of manufacture is explained by the fact that the profits accruing from the old, clumsy, crude, and wasteful process were so large that the proprietors could see no possible reason for welcoming innovations. Moreover, the manufacture under established conditions was in the hands of a comparatively small number of makers, who could not adopt new measures without letting in more men, and the long tenure of their monopoly made the salt-men intolerant of a competitive system. Opposition was so abominable to them that, while they would combine as one man to keep out the daring intruder, or to crush such an one if he succeeded in getting in, they were not at all averse from employing similar tactics for the purpose of exterminating one another. Although it had cost them over a quarter of a million sterling to dispose of William Furnival, the game of price-cutting was not discontinued after 1833. In order to safeguard themselves against the periodical falls in prices, which, if persisted in, would mean wholesale ruin, all sorts of associations, syndicates, trusts, committees, and pools were formed for the regulation of stocks and prices, but each successive combination was successively abandoned, and was followed by another period of bitter jealousy and trading loss. Between 1846 and 1880, the trade was being continually reorganized for offensive and defensive commercial purposes, but, in 1881, it was admitted that, in spite of all attempts to encourage a better feeling among the leading manufacturers, “the spirit of envy, hate, malice, and all uncharitableness, which has so long been the bane of the salt trade, has again become rampant,” with the result that the price of common salt—4s., less the brokers’ discount of 5 per cent.—was the lowest that it had touched since the American Civil War. Two years later it was declared that the trade, instead of being ruled by common sense and business experience, was being ruined by personal animosities and trade jealousies.