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gined I have mistaken his ideas, I will take the liberty of giving the fubftance of this paper, and of making fuch extras from it as may ferve to fhew that he entertains the fentiments which I have imputed to him.

The author begins by ftating the importance of the alt-rade to the United ·States. He goes on to fay, that "though the falt fprings in New York, Ohio, Kentucky, &c. furnish the interior with large quantities of muriate of soda, ftill by far the greatest proportion of the falt confumed is brought from abroad." The total quantity imported into America, from October 1, 1800, to September 30, 1801, was 3,282,063 bushels, of 56 lb. to the bufhel. Of this quantity, 1,269,398 bufhels, or rather more than one-third of the whole quantity imported, was brought from England, and was of English manufacture. He then states, “ that the British fait imported into the United States comes chiefly from Cheshire, from the mines which contain it. It is found there near Northwich. The firft was dif covered in boring for coal, in 1670, by one John Jackson. Rock flt, and the white-falt made from it, are exported free from duty."

"Northwich rock-falt is never used in its crude state at table; and the employment of it for pickling, or curing fleth or fifh, or preferving any provisions, without being previously diffolved in water, and boiled down into a white falt, is prohibited under a penalty of forty fhillings for every pound of rock-falt fo applied.They use the rock-falt for ftrengthening brine-fprings, or fea-water, preparatory to boiling down."

"The white fine filt is prepared by a boiling heat. Sea-water, brine-fprings, and rock-falt, generally abound with various other earthy and faline ingredients, fuch as lime, magnefia, Epfom falts, gypfum, Glauber's falts, &c. all of which injure the quality of the salt, and difqualify it for preferving animal-fleh every where, but especially in hot counties and feafons. Therefore the British falt, which comes to us chiefly from Liverpool and the Merfey, is a molt pernicious article of import. It is both weak and impure; and, deceived by its tempting appearance, the Americans have ufed it for curing their fifh, beef, pork, and butter. In fuch cafes, thefe kinds of provili ns have generally spoiled, and become putrid. The feptic (i. e. putrid,) gaffes, exhaling therefrom, poifon the atmosphere of our cities and fhips, and in

feet the people with peftilential diseases; the way to avoid which is to avoid Liverpool falt."

The author's philippic against British falt does not end here. After enumerating the other fources from which America derives its fea-falt, which are chiefly the Weft Indies and Portugal, he adds "Thefe kinds of falt, any indeed that we import, befides that from Liverpool, may be employed with fafety in preferving animal-flesh for food; but that Britifh falt, which they make to fell abroad, and not to confume at home, ought to be fhunned, as a moft pernicious article in trade, and the caufe of incalculable sicknels, death, and lofs of property, among the American confumers."

He goes on to fay, "As foon as the ufe of British falt is discontinued, there will be lefs corruption of the provisions, which form so great a part of our WeftIndia exports; there will be lefs feptic and venomous air engendered in the veffels which contain them; there will be proportionally lefs fickness and mortality from their mifchievous agency; and of course there will be lefs and lefs neife about importing yellow-fevers, &c. from the tropical latitudes. Thus, by degrees, we fhall learn not to blame the West Indies for our own mifdo ngs. The evil lies chiefly at home, and in our own veffels; and this is one of the modes of correction and prevention.".

On reading the first part of this paper, I was led to imagine that the object of the author, in levelling his abufe at the falt of foreign manufacture, was to induce his countrymen to improve the advantages which nature had afforded them, and to fhew them that they might manufacture a falt of fuperior quality from their own brine-springs ; an object in itfelf laudable. On proceeding, however, with the paper, I was soon aware of my error, and found that this was far from being the design of the author: that he allowed the Americans freely to use falt imported from any other country; whilft he afcribed to that of British manufacture all the long catalogue of evils which he enumerates.

Without entering into the motives of this inveterate and exclufive hoftility. against Brith falt, I fhall briefly mention what the falt is that is exported to America, and examine the proofs adduced of its impurity, and confequent weakness.

That the quantity of white-falt which has been exported from Great Britain to

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the United States, in twelve months, has been at least equal to what is ftated by the author of this paper, there can be little doubt. From an account which was ordered to be laid on the table of the Houfe of Commons, of the rock and white-falt exported from Great Britain to different countries, for feveral years, it appears, that, from January 5, 1801, to January 5, 1802, 1,946,321 bushels of White-falt were exported to the States of America. Large as this quantity feems, it constituted a very fmall proportion of the total export of falt from Great Britain, which amounted in that year to 6,582,329 bushes. The mere duy on the falt confumed at home, which is used in curing of fish and provifions, in preferving buter, in the making of cheese, and for all domeftic purpofes,* amounted to little lefs than a million ferling. Is it not fingular, that, from the United States alone, we should have heard of the dreadful effects which the importation of this "pernicious article has occafioned?" though it has been fent in fuch large quantities to different European States, to Africa, to our own American colonies: though it has been used in our own fisheries, and in curing the provifions for our navy: yet no yellow fever, no peftilential disease, has been here produced by it :-pretty ftrong proofs that this falt is not difqualified for preferving animal-fleth" every where. Why in America alone its baneful effects fhould fhew themselves, it is not eafy to conceive!

From the account which the author next gives of the discovery of reck-falt in Cheshire, he feems to imagine, either that the falt is fent to America in the ftate in which it is procured from the mines "the British falt imported into America comes chiefly from Cheshire, from the mines which contain it," or that it is manufactured principally from the "rockfalt ufed in ftrengthening brine-fprings or fea-water, preparatory to boiling down." He appears to fuppofe that no white-falt was manufactured in Cheshire previous to the accidental difcovery of rock-falt.Whether thefe are his ideas, or whether they are facts, may not be of importance in difcuffing the question of the compara tive purity of Liverpool falt, but the truth is, that no rock-falt, or falt in the ftate in which it is gotten from the mines,

* No mention is here made of the falt ufed in manufactures, as this is unconnected with the subject of the prefent inquiry.

is ever exported to the United States, though very large quantities of it are annually exported to other countries; and that by far the greatest proportion of the whitefalt exported from England, or used at home, is manufactured from the natural brine fprings, without any artificial addition of rock-falt, and has been procured from thefe fources as long as we have any records of the hiftory of the country.After having, however, endeavoured to give the idea, that it is only the "fait from the mines," or falt prepared from this, which is exported from England into America, he feems, in introducing the account of the penalty attached to the use of crude rock-falt in England, to wish to lead his readers to believe, that, though the English are very ready to supply the Americans with this, they take care not to use it themselves. That he wishes to imprefs upon them this idea, we are juftified in supposing from what he afterwards iays, "but that British falt, which they make to fell abroad, and not to confume at home, ought to be shunned as a molt pernicious art cle in trade," &c.

What is the difference alluded to, it is for the author to explain. In England it it is perfectly well known that no diftinetion is made, no difference known, betwixt the falt exported and that confumed at home; while England efcapes all the terrible evils afcribed to this manufacture. It is hardly neceffary to ftate, that the penalty on the ufe of rock-falt is intended merely to prevent frauds on the revenue.

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The next part of the paper feems to contain the ground-work of the author's charge against falt of British manufac ture; and the inference which he produces from the premiles he gives us, is furely. not a little fingular and extraordinary !— "Sea-falt, brine-fprings, and rock-falt, generally abound with various earthy and faline ingredients, fuch as lime, magnefia, Epfom falt, gypsum, Glauber's falts, &c. all of wh ch injure the quality of the falt, and difqualify it for preferving animal-fleth every where, but especially in hot countries and feafons. Therefore this British falt, which 'comes to us chiefly from Liverpool and the Merfey, is a moft pernicious article of import. It is both weak and impu e," &c.

That fea water, brine-fprings, and rock-salt, each contain, befides muriate of foda, various earthy and falne ingredients, often those which the author of this paper enumerates, is perfectly well known. But before he had prefented us with the conclufion he draws, we might

have

have expected that he would have fhewn us, either that the falt imported into America from other countries, was procured from other and purer fources, or that the Cheshire falt, exported from Liverpool, contained a larger proportion of these earthy impurities, than the falt received from other quarters. Can the author be fo ignorant of the subject about which he writes, as not to know that falt is procured in the large way from no other fources than fea-water, brine-fprings, and rock-falt, (or, in fome countries, from inland falt lakes, which partake of the nature of the former fources,) and that the Portugal and Mediterranean falt is obtained by flow evaporation of fea-water alone; whilft the Chefhire-falt is procured from native brine-(prings and rockfalt? In his eagerness to vilify the falt of British manufacture, he has, with fingular inconfitency, included all kinds of falt in the fame indifcriminate cenfure; for, fince all the fources of manufactured falt 'contain the'e impurities, and fince the author attributes to thefe impurities an imperfection in the power of preferving animal-flesh, the fair inference would be, not that Liverpool falt alone must be weak and impure, but that every kind of falt is unfit for the prefervation of animal food in hot climates, and is therefore "a moft pernicions article of import."

But had the author given himself the trouble of examining into the component parts of Cheshire falt, he would have dif covered that this very falt, which he fates to be neceffarily fo impure, is almost entirely free from thofe earthy falts, which he ftats to be contained in the various fources whence muriate of foda is ex. tracted; and he would have learnt, that even the rock-falt found in England confifts of pure muriate of foja, combined with a certain proportion of argillaceous earth, with fcarcely any other earthy or faline admixture. The argillaceous earth, being perfectly infoluble in water, is com pletely feparated when the rock-falt is diffolved; and if any earthy matter be found mixed with the falt afterwards mad, it can be derived only from the water by which the folution is formed. In the natural brine fprings, which owe their ori

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gin to the waters of the furface finding their way through the fuperincumbent earth to a stratum of rock-falt, and diffolving a certain portion of this, (greater or lefs as it is more or lefs expofed to their action,) the brine contains fcarcely any more earthy matter than the water did previous to its action on the falt, or no more than the water of springs or rivers.

It is certainly only by experiment that the relative purity of the different falts, and of the different fources from which they are procured, can be ascertained.Such experiments we have, and the following are their results:

First, with regard to the comparative purity of the fources whence the different kinds of falt are obtained; the bay falt is procured entirely from fea-water, and the Cheshire falt from the brine-fprings and rock-falt in that part of England. The rock-falt, as we fhall prefently fhew, contains few other foluble parts than pure muriate of foda, and therefore the proper fübjects for comparison are the Cheshirebrine and fea-water.

To our ingenious countryman, Mr. William Henry, whose chemical knowledge and accuracy of research are well known, we are indebted for an examination of the brine from the springs at Northwich.

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Examining it by re-agents, he found": 1. That muriate of barytes gave a white precipitate."

2. That there was a precipitation on the addition of oxalic acid.

3. That with pruffiate of potash there was no immediate change, but after fome hours the brine acquired a blue tinge.

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4. That all the aikalies, fixed and volatile, threw down an abundant white precipitate:

The first and fecond experiments indicate fulphate of lime, and the third, an inconfiderable quantity of iron.

All the earths were precipitated from two quarts of brine, by carbonate of potash. This precipitate, washed and dried, weighed two hundred grains, and con fifted of a mixture of carbonate of lime and carbonate of magnefia, principally the former. The muriate of foda in the fame quantity of brine was 20 oz. 256 grains.”

Hence it appears, that a wine-pint of grains, of muriate of foda, together with a the brine contains 5 oz. 64 gr. or 2464 quantity of earthy falts, which are to be confidered as impurities, and of which the mere earthy part, brought to the state of a carbonate, amounts to 50 grains. On the other hand, we have an analyfis of

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of fea-water by the illuftrious Bergman, whofe authority ftands among the very highest as a practical operator. This excellent chemist ascertained the contents of fea-water to be the following, (reducing the measures from the Swedish to the English, for the fake of comparifo: ): ' One English wine pint of fea-water, taken up at the latitude of the Canaries, contains:

Of common falt
Of muriated magnesia
Of fulphate of lime

grains.

241

65 8

Of these three ingredients, the two laft are the earthy impurities, from which, if the earth were precipitated by a carbon ated alkali, as in the former experiments, the 65 grains of muriated magnefia would yield 45 grains, and the 8 grains of fulphate of lime would yield about 6 grains of earth total 51 grains.

Thus we fee that the abfolute quantity of earth precipitable from a pint of Chefhire-brine, is nearly the fame as from a pint of fea-water; but the relative proportion of this earth to the pure muriate of foda, is totally different; fince a given bulk of the Chefhire brine contains full ten times as much pure falt as the fame quantity of fea-water. Confequently it would be neceffary to evap rate at least ten times as much fea-water as Cheshire-brine, to obtain a pound of falt ; and, therefore, if the impurity of the fource whence falt is obtained were to affect the quality of the manufactured product, as the author of the paper infinuates, it would follow that the bay-falt, which is procured from feawater, ought to contain ten times the impurity of that of Cheshire manufacture, which is fo much reprobated.

The following experiments will fhew how fmall is the proportion of earthy falt contained in rock falt, or in the falt which is procured from the Cheshire brine-fprings, either natural, or when ftrengthened with rock falt. They will convince us, that if this last be not found to preferve animal fubftances from putrefaction, at least equally well with other falts, it cannot be owing to the want of purity in the falt, but must be ascribed to fome other caufe.

·Experiments.-480 Grains of rock-falt were diffolved in four ounces of diftilled

water.

1. On addition of carbonate of potash, there was no precipitare.

2. No alteration was produced by this folution on blue vegetable juices.

3. On addition of a few drops of tinc

ture of gals, a flight purple tinge was given to the solution; and, after standing fome hours, th re was a brown fed.ment at the bottom of the phial.

4. On addition of muriate of barytes, no pr cipita e.

The fift experiment fhews that the rock-falt has no inuria e of lime or muriate of magnesia combined with it, earthy falts always met with in fea-water, and generally in brine. The fecond that it has no uncombined acid or alkali. The third, that it contains fome portion of iron. The fourth, that there is no fulphate of Time (gypfum) contained in it.

Though the prefence of a fmall quantity of iron gives a brownish tinge to a large quantity of falt, it has never been fufpected to injure the quality of the falt, or to leffen its power of refifting putrefaction. The iron here found is a carbonate; and if the brine be left for a few days in the reservoir, previous to its being drawn into the evaporating-pan, the greater part of the acid leaves the iron, and the oxyd fubfides to the bottom of he citern. If any ft remain united with the acid, when the brine is heated to 100 degrees of Fahrenheit in the evaporatingpan, the acid quits the iron, and the latter then fubfides. As the oxyd of iron affects only the colour, and does not diminish the ufe of the falt, lefs pains is taken to separate it.*

Similar experiments made with folutions of foved (or fine-grained), falt, and with large-grained (fishery) salt, of Cheshire manufacture, fuch as are indifcriminately exported or used in England, fhew, that the portion of earthy-falts contained in them is much too small to have any effect in leffening the value of the falt, and much smaller than is met with in falt of any other manufacture.

Experiment.-480 Grains of ftovedfalt (prepared by a boiling-heat) were diffolved in 4 oz. of distilled water.

1. A precipitate was produced by a folution of carbonate of potash, which, when dried, amounted to 3 grains, and was found to confift of carbonate of lime and carbonate of magnesia.

2. On adding muriate of barytes, there was a white precipirate.

3. No alteration was produced by a fimilar folution on blue vegetable juice;

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but on adding to it a fingle drop of muriatic-acid, a fentible redness was given.➡ By the addition of a few drops of a folu tion of carbonate of potash to a like folution of stoved-falt, a light green col ur was given to the blue juice of vegerables.

On making finlar experiments with a folution of 480 grains of large grained fifhery-falt, prepared by an evaporation conducted at 110 degrees of Fahrenheit, the refult was the fame, excepting that the precipitate, on the addition of the folution of carbonate of potash, amounted to one grain onlv.

From the first experiment it appears, that there is a fimall quantity of muriated lime and magnefia combined with each kind of falt; but that even in the ftoved, or the falt prepared by a boiling-heat, thefe do not amount to part of the muriate of soda; and in the large-grained, to little more than soo part. The fecond experiment fhews that fome fulphate of lime is in the falt; but as this is foluble in water only in the proportion of 1 to 500, it is obvious how fmall the quantity of this must neceffarily be and

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* It may here be remarked, that the proportion of earthy-falts to the muriate of foda,

is ftill fmaller in the manufactured-falt than

in the brine, small as it is even in the latter; for on the application of heat to the brine, a portion of the acid may be obferved to leave the carbonate of lime, and this is no longer held in folution; while, as the evaporation proceeds, the fulphate of lime fubfides, and mixes with the carbonate of lime which has been feparated. Thefe earthy falts are partly taken out in the early stage of the process of manufacture, with a portion of the muriate of foda first formed, by the operation of "clearing" the pan; and partly fubfide and adhere to the upper furface of the pan, forming that incrustation there which is called by the workmen panfcratch," or "fcale," and which gradually accumulating, it becomes neceffary to remove from the pan every three or four weeks by "picking."

From an analyfis of the " clearings," by the excellent chemift above-mentioned, Mr. William Henry, it appears that 480 parts contained 384 of muriate of foda, 20 of carbonate of lime, and 76 of fulphate of lime.— He found 430 parts of the "pickings" to contain 40 of muriate of foda, 60 of carboAate, and 380 of fulphate of lime. Circumftances are, of course, occurring to vary these proportions. No muriate of magnesia is found in either the clearings or pickings, fince this, being much more ready of folution than muriate of foda, remains in the liquor left at the bottom of the pan after the muriate of foda has been drawn out,

as it has appeared that none is contained in the rock falt, what little, there is of it can be derived only from the water of folution, and can contain no more than this. No one will, I believe, be found to fufpect that the mail portion there is of it can injure the quality of the fait.

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The tourd experiment thews, that there or either in the foved, or the largegrained fishery-falt, any uncombined acid or alkali.

It was an idea of the late Dr. Brownrigg, when he publified his ingenious and philofophical work on the Manufac ture of common Salt, that by a boilingheat, a portion of the acid in the muriate of foda was expelled, and that the falt prepared in this procefs had an excess of alkali. The learned Bishop of Llandaff seems to have entertained the fame opinion.He afcribes the fuppofed fuperiority of Dutch falt to the addition of four whey which they make to the brine, and which, he imagines, unites with any uncombined alkali in it. The above expe riment, which was frequently repeated, fhews that this is not the cafe. It correSpons with the experiments made by Mr. Boyle, and proves that no feparation takes place in the component parts of the muriate of joda by boiling the brine.

ti ned, and the statement of facts which The experiments which have been menhas been given, muft, we prefume, have convinced every unprejudiced perfon that the lait manufactured in Chefhire is almost entirely free from any foreign contents, and that it confifts of pure muriate of foda, with fcarcely any other faline or earthy addition. But, though more pure than any other falt manufactured, it does not neceffarily follow, that, in every form in which it is prepared, it should poffefs superior advantages in the prefervation of animal-food, fince feveral other circum ftances are here to be taken into confideration. These will be belt understood by examining what is the procefs of nature in forming the crystals of muriate of foda; and by stating the different ways in which the manufacture is conducted in Cheshire.

The natural form of the crystals of muriate of soda, is that of a perfect cube; and they regularly affume this figure, when the due arrangement of their par ticles has not been interrupted by agitation, or the application of ftrong heat. "Thefe cubes exhibit diagonal strie, and frequently, on each fide, produce fquares parallel to the external furface, gradually decreafing inwards, circumftances which

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