SAL
SAL
pit-coal is lighted in the furnace, and then, for a pan which contains about fourteen hundred gallons, the fait boiler takes the whites of three eggs, and incorporates them all with two or three gallons of fea water, which he pours into the fait pan, while the water contained therein is only luke- warm, and mixes this with the reft by ftirring it about with a rake. In many places they ufe inftead of eggs the blood of flieep or oxen to clarify the fea water ; and in Scotland they do not give themfelves the trouble of clarifying it at all. As the water heats, there arifes a black frothy fcum upon it, which is to betaken off with wooden fkimmers. After this the water appears perfectly clear, and by boiling it brifkly about four hours, a pan loaded in the common way, that is about fifteen inches deep, will begin to form cryftals upon itsfurface. The pan is then filled up a fecond time with frefh fea water; and about the time when it is half filled, the fcratch pans are taken out and emptied of a white powder, feeming a kind of calcarious earth, which feparates itfelf from the fea water, during its boiling before the fait begins to moot. When" thefe have been emptied, they are again put into their places, where they are afterwards filled again. This powder being violently agitated by the boiling liquor, does not fubfide till it comes to the corners of the pan where the motion of the mafs is fmaller, and it there falls into thefe pans placed on purpofe to receive it. The fecond filling of the pan is boiled down after clarifying in the fame manner as the firft, and fo a third and a fourth ; but in the evaporation of the fourth, when the cryftals begin to form themfelves, they flacken the fire, and only keep the liquor fimmering. In this heat they keep it all the while that the fait is granulating, which is nine or ten hours. The granules or cryftals all fall to the bottom of the pan ; and when the water is almoft all evaporated, and the fait lies nearly dry at the bottom, they rake it all together into a long heap on one fide of 'the pan, where it lies a while to drain from the brine, and then is put into barrows and car- ried to the ftore-houfe, and delivered into the cuftody of his majefty's officers. In this manner the whole procefs is ufually performed in twenty-four hours, the fait being com- monly drawn out every morning. This is the method in molt of our fait works, but in fome they fill the pan feven times before they boil up the fait, and fo take it out but once in two days, or five times in a fortnight. In the common way of four boilings, a pan of the ufual fize, containing one thoufand three hundred gallons, they draw from fifteen to twenty bufhels of fait every day, each buftiel weighing fifty- fix pounds.
When the fait is carried into the ftore-houfe it is put into drabs, which are partitions, like ftalls for horfes, lined at three fides, and the bottom with boards, and having a Aid- ing board on the forefide to draw up on occafion. The bottoms are made Shelving, being higheft at the back, and gradually inclining forward ; by this means the brine re- maining among the fait, cafily feparates and runs from it, and the fait in three or four days becomes fufficiently dry ; in fome places they ufe cribs and barrows, which are long and co- nic wicker bafkets for this purpofe, and in fome places wooden troughs with holes in the bottom. The faline li- quor which remains from the making of fait is what is called bittern. See the article Bittern.
The fides of the pans in which the fait is made, are foon crufted over with the fame fort of matter formed into cakes or cruils, that falls in powder into the fcratch pans ; this the workmen call ftone fcratch ; they are obliged to cleanfe the pans of it once in a week or ten days, otherwife they will be burnt : in England they do this with iron picks, but at Hall in Saxony they have a much better method ; for they then take out the pans, and turning them bottom upwards, burn ftraw under them, by which means the matter of the cruft loofens itfelf, and after this it falls off on being ftruck with a mallet or hammer. Brownrig of Salt, p. 62. In Lancashire, and forne other parts of England, fczfalt is made in this manner : they pare off, in dry weather, in fum- mer, the furface of the flats, which are covered at full fea, and bare when the tide is out. When they have procured heaps of this they put it into troughs, and pour frefh water on it; this wafhes oft the fait that hung about the fand, and is received fo impregnated into veflels (et underneath the troughs. So long as this liquor is ftrong enough to bear an egg they put on more water ; when an egg finks in it they throw the fand out of the troughs, and put in frefh from the heaps. The water thus impregnated with fait they boil in leaden pans, and evaporate toadrynefs, the fait remaining behind. Ray's Englifh word, p. 179. Rock Salt, a name given by the common people of England to the foflile fait, or fal gem, found in feveral parts of the worjd.
It was in the year 1670 that we firft difcovered the mines of rock fait in Chefhire, where it was accidentally found on the lands of Mr. Marbury, of Marbury, in that county, in boring for coal. It lay there thirty-three or thirty-four yards from the furface, and there iflued from it a vigorous {harp brine ftronger than any of the Chefhire fait fprings before known afforded. Since that many other mines of it
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have been found in the fame county, and a great many are now worked by a company of proprietors, and yield vaft quantities of fait \ but this is efteemed unfit for domeftic ufes in its natural ftate, and for that reafon the proprietors ufe the method practifed in Poland, Hungary, and many other places on the coarfer rock fait, that is, the refining it, by diffolving it in weak brine, and then boiling it into fait again ; this is done with great quantities on the fpot ; and beftde this great quantities are carried in the rough Hate to Liverpool, and there refined with the water of the river Merfey at full fea, or elfe fhipped at Liverpool, and thence tranfported to other parts of England and Ireland, where it is wrought into fait with fea water.
The rock fait refined upon the fpot is alfo exported to Ire- land ; and in times of war, to our American colonies, when they cannot have bay fait. The works wheie they refine the rock fait are called refineries, and the rock fait is broken fmall and put into leaden cifterns, where it is diflblved cold in fea water. When the folution has ftood a day and night to fettle, it is drawn off from the fediment into the fait pan, and refined into fait in the fame manner that common brine is boiled up. The fame additions are ufed in the clarifying it, and the fcratch or calcarious matter falling from it, forms a cruft as in the other works. The brine left in the pans after the fait is taken out is not thrown away, but is added to the next quantity put into the pan, and fo on to the end of the works. Brownrig on Salt,
P- J39-
In Hungary, near the city of Eperes, they have a very re- markable mine of th\s fait which fupphes the whole country thereabout. The-mine is near two hundred fathoms deep, and in the greaieft part is funk through earth, not through rock. The veins of fait are fo large, that there are many blocks of it weighing two thoufand pounds, fome of ten or more. The fait is ufually hewn out into long fquare pieces of about two feet, and is afterwards ground between two grindftones, to reduce it to a powder fit for ufe. Though the mines of fait are ufuaily cold and damp, yet the fait it- felf being very folid, and in the rock or mafs, is feldom much affected by the dampnefs. The fait in many of the mines is not of a fine white, but fuch as is of a dufky grey in the mafs, often becomes very white when powdered, and made fit for ufe. Salt upon Salt, a name given to a kind of common/^// pre- pared by the Dutch, of great ufe in preferving herrings and other fifh, and to which they principally owe their advan- tages in the herring trade. The Dutch prepa e two kinds of refined fait, one of a fmall grain, intended for the ufe of the table, and called butter fait. They export large quanti- ties of this to the countries upon the Rhine, and into other parts of Germany. The other kind is a very ftrong and pure fait, and is of the largeft grain of any boiled fait, now- made : this laft they call the St. Ubes or Lifbon fait, from its refemblance to the pure bay fait made in thofe places. The fait, which they refine, is altogether marine bay falt> and they chiefly have it from France and Spain ; but they find, by experience, that any one kind of bay fait does not anfwer their purpofes, fo well as two or more kinds ; they therefore frequently mix three parts of Cadiz fait with one part of that of SoufVon, which is of great ftrength, but very dirty, and of a green colour, and docs not coft above half the price of the Spanifh fait ; for difiblving the bay fait, they ufe fea water, which they bring in lighters to Dort and Rotterdam from below the Brill or Hel- voet ; out of thefe lighters it is craned into cellars, and is thus impregnated with bay fait to a certain degree of ftrength, which they determine by hydrometers made for that purpofe. After the heavy drofs of the fait is fubfided to the bottom of the cellar, the clear brine is pumpted up into the fait pan through a mat, which retains the light fcum, ftraws, or other impurities, which floated on the fur- face of it. Thefe fait pans are of iron, of a round figure, and commonly forty feet in diameter, and eighteen inches deep. Thefe pans are placed over a hearth furnace, and the only fuel they ufe in the boiling the fait is dry turf. The fire is kept up fo high, that the liquor boils brifkly all the time, and if any fcum aiifes, they carefully take it off, but they ufe no clarifying mixtures. A little before the fait be- gins to granulate, they add to the pan a lump of butter, of the bignefs of a walnut, and half a pint of four whey, which has ftood at leaft half a year. When thefe things are per- fectly mixed in by a good ftirring, they fhut the doors and windows of the houfe, that no air can blow in cold, and the houfe is kept thus hot all the time that the fait is form- ing. This method is not new, or peculiar to the Dutch works, for Agricola defcribes an apparatus of boards, to keep the cold air out of the fait pan all the time that the fait is forming; and the Germans ufe it In many places at this time.
It is out of this fame brine, and by the fame procefs, that they make the table fait and the ftrong fait ; only toward the end of the procefs they make this difference, if the pan is to be wrought into table fait, the brine is kept gently fim- mering during the whole operation, and all is finifhed in
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