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dern improvements in chemistry were made, a great part of the acid escaped for want of water to combine with; but by the use of Woulfe's apparatus, (See LABORATORY,) the acid air is made to pass through water, in which it is nearly condensed, and forms muriatic acid of double the weight of the water, though the bulk of this fluid is increased one-half only. The acid condensed in the first receiver, which contains no water, is of a yellow colour, arising from the impurities of the salt.

The marine acid in commerce has a straw colour: but this is owing to accidental impurity; for it does not obtain in the acid produced by the impregnation of water with the pure aëriform acid.

The muriatic acid is one of those longest known, and some of its compounds are among those salts with which we are most familiar.

* The muriates, when in a state of dryness, are actually chlorides, consisting of chlorine and the metal; but since moisture makes them instantly pass to the state of muriates, we shall describe them under this article. The sulphates and nitrates, when destitute of water, may in like manner be regarded as containing neither acid nor alkali, and might therefore be transported to some new department of classification, to be styled sulphides and nitrides, as we shall see in treating of salts.*

The muriate of barytes crystallizes in tables bevelled at the edges, or in octaëdral pyramids applied base to base. It is soluble in five parts of water at 60°, in still less at a boiling heat, and also in alcohol. It is not altered in the air, and but partly decomposable by heat. The sulphuric acid separates its base; and the alkaline carbomates and sulphates decompose it by double affinity. It is best prepared by dissolving the carbonate in dilute muriatic acid; and if contaminated with iron or lead, which occasionally happens, these may be separated by the addition of a small quantity of liquid ammonia, or by boiling and stirring the solution with a little barytes. Mr. Goettling recommends to prepare it from the sulphate of barytes: eight parts of which in fine powder are to be mixed with two of muriate of soda, and one of charcoal powder. This is to be pressed hard into a Hessian crucible, and exposed for an hour and a half to a red heat in a wind furnace. The cold mass, being powdered, is to be boiled a minute or two in sixteen parts of water, and then filtered. To this liquor muriatic acid is to be added by little and little, till sulphuretted hydrogen ceases to be evolved; it is then to be filtered, a little hot water to be poured on the residuum, the liquor evaporated to a pellicle, filtered again, and then set to crystallize. As the muriate of soda is much

more soluble than the muriate of barytes, and does not separate by cooling, the muriate of barytes will crystallize into a perfectly white salt, and leave the muriate of soda in the mother water, which may be evaporated repeatedly till no more muriate of barytes is obtained. This salt was first employed in medicine by Dr. Crawford, chiefly in scrofulous complaints and cancer, beginning with doses of a few drops of the saturated solution twice a-day, and increasing it gradually, as far as forty or fifty drops in some instances. In large doses it excites nausea, and has deleterious effects. Fourcroy says it has been found very successful in scrofula in France. It has likewise been recommended as a vermifuge; and it has been given with much apparent advantage, even to very young children, where the usual symptoms of worms occurred, though none were ascertained to be present. As a test of sulphuric acid it is of great use.

The muriate of potash, formerly known by the names of febrifuge salt of Sylvius, digestive salt, and regenerated sea salt, crystallizes in regular cubes, or in rectangular parallelopipedons; decrepitating on the fire, without losing much of their acid, and acquiring a little moisture from damp air, and giving it out again in dry. Their taste is saline and bitter. They are soluble in thrice their weight of cold water, and in but little less of boiling water, so as to require spontaneous evaporation for crystallizing. Fourcroy recommends, to cover the vessel with gauze, and suspend hairs in it, for the purpose of obtaining regular crystals.

It is sometimes prepared in decomposing sea salt by common potash for the purpose of obtaining soda; and may be formed by the direct combination of its constituent parts.

It is decomposable by the sulphuric and nitric acids. Barytes decomposes it, though not completely. And both silex and alumina decomposed it partially in the dry way. It decomposes the earthy nitrates, so that it might be used in saltpetre manufactories to decompose the nitrate of lime. Muriate of soda, or common salt, is of considerable use in the arts, as well as a necessary ingredient in our food. It crystallizes in cubes, which are sometimes grouped together in various ways, and not unfrequently form hollow quadrangular pyramids. In the fire it decrepitates, melts, and is at length volatilized. When pure it is not deliquescent. One part is soluble in 24 of cold water, and in little less of hot, so that it cannot be e crystallized but by by evaporation. According to M. Chenevix, it is soluble in alcohol also, particularly when it is mixed with the chlorate.

Common salt is found in large masses, or

in rocks under the earth, in England and elsewhere. In the solid form it is called sal gem or rock salt. If it be pure and transparent, it may be immediately used in the state in which it is found; but if it contain any impure earthy particles, it should be previously freed from them. In some countries it is found in incredible quantities, and dug up like metals from the bowels of the earth. In this manner has this salt been dug out of the celebrated salt mines near Bochnia and Wieliczka, in Poland, ever since the middle of the 13th century, consequently above these 500 years, in such amazing quantities, that sometimes there have been 20,000 tons ready for sale. In these mines, which are said to reach to the depth of several hundred fathoms, 500 men are constantly employed. The pure and transparent salt needs no other preparation than to be beaten to small pieces, or ground in a mill. But that which is more impure must be elutriated, purified, and boiled. That which is quite impure, and full of small stones, is sold under the name of rock salt, and is applied to ordinary uses; it may likewise be used for strengthening weak and poor brine-springs.

Though the salt mines of Wieliczka, near Cracow in Poland, have long astonished the philosopher and traveller, yet it deserves to be remarked, that the quantity of rock salt obtained from the mines of Northwich is greatly superior to that obtained at Cracow. The bishop of Llandaff affirms, that a single pit, into which he descended, yielded at a medium 4000 tons of salt in a year, which alone is about two-thirds of that raised in the Polish mines. This rock salt is never used on our tables in its crude state, as the Polish rock salt is; and though the pure transparent salt might be used with our food, with out any danger, yet it is prohibited under a penalty of 40s. for every pound of rock salt so applied. It is partly purified in water, and a great part of it is sent to Liverpool and other places, where it is used either for strengthening brine-springs or

sea water.

Beside the salt mines here mentioned, where the common salt is found in a concrete state, under the name of rock salt, there is at Cordova, in the province of Catalonia in Spain, a remarkable solid mountain of rock salt; this mountain is between four and five hundred feet in height, and a league in circuit; its depth below the surface of the earth is not known. This mountain contains the rock salt without the least admixture of any other matter.

The waters of the ocean every where abound with common salt, though in different proportions. The water of the Baltre sea is said to contain one sixty-fourth

of its weight of salt; that of the sea be tween England and Flanders contains one thirty-second part; that on the coast of Spain one sixteenth part; and between the tropics it is said, erroneously, to contain from an eleventh to an eighth part.

The water of the sea contains, besides the common salt, a considerable proportion of muriate of magnesia, and some sulphate of lime, of soda, and potash. The former is the chief ingredient of the remaining liquid which is left after the extraction of the common salt, and is called the mother water. Sea water, if taken up near the surface, contains also the putrid remains of animal substances, which render it nauseous, and in a long continued calm cause the sea to stink.

The whole art of extracting salt from waters which contain it, consists in evaporating the water in the cheapest and most convenient manner. In England, a brine composed of sea water, with the addition of rock salt, is evaporated in large shallow iron boilers; and the crystals of salt are taken out in baskets. In Russia, and probably in other northern countries, the sea water is exposed to freeze; and the ice, which is almost entirely fresh, being taken out, the remaining brine is much stronger, and is evaporated by boiling. In the southern parts of Europe the salt-makers take advantage of spontaneous evaporation. A flat piece of ground near the sea is chosen, and banked round, to prevent its being overflowed at high water. The space within the banks is divided by low walls into several compartments, which successively communicate with each other. At flood tide, the first of these is filled with sea water; which, by remaining a certain time, deposites its impurities, and loses part of its aqueous fluid. The residue is then suffered to run into the next compartment; and the former is again filled as before. From the second compartment, after a due time, the water is transferred into a third, which is lined with clay well rammed and levelled. At this period the evaporation is usually brought to that degree, that a crust of salt is formed on the surface of the water, which the workmen break, and it immediately falls to the bottom. They continue to do this, until the quantity is sufficient to be raked out, and dried in heaps. This is called bay salt.

In some parts of France, and also on the coast of China, they wash the dried sands of the sea with a small proportion of water, and evaporate this brine in leaden boilers.

There is no difference between this salt and the lake salt extracted from different lakes, excepting such as may be occasioned by the casual intervention of some sub

stances. In this respect the Jeltonic salt water lake, in the Russian dominions, near Saratow and Dmitrewsk, deserves our attention. In the year 1748, when the Russians first fetched salt thence, the lake was almost solid with salt; and that to such a degree, that they drove their heavy wagons over it, as over a frozen river, and broke up the salt.f But since the year 1757 the water has increased so much, that at this time it is nothing more than a lake very strongly impregnated with salt. The Jeltonic lake salt contains at the same time alum and sulphate of magnesia.

At several places in Germany, and at Montmarot in France, the waters of salt springs are pumped up to a large reservoir at the top of a building or shed; from which it drops or trickles through small apertures upon boards covered with brushwood. The large surface of the water thus exposed to the air causes a very considerable evaporation; and the brine is afterward conveyed to the boilers for the perfect separation of the salt.

To free common salt from those mixtures that render it deliquescent, and less fit for the purposes to which it is applied, it may be put into a conical vessel with a small aperture at the point, and a saturated solution of the muriate of soda boiling hot be poured on it. This solution will dissolve and carry off any other salt mixed with the muriate of soda, and leave it quite pure, by repeating the process three ør four times.

From this salt, as already observed, the muriatic acid is extracted; and of late years to obtain its base separate, in the most economical mode, for the purposes of the arts, has been an object of research. The process of Scheele, which consists in mixing the muriate of soda with red oxide of lead, making this into a soft paste with water, and allowing it to stand thus for some time, moistening it with water as it gets dry, and then separating the soda from the muriate of lead by lixiviation, has been resorted to in this country. Mr. Turner some years ago had a patent for it; converting the muriate of lead into a a pigment, which was termed mineral or patent yelow, by heating it to fusion. The oxide of lead should be at least twice the weight of the salt. This would have answered extremely well, had there been an adequate and regular demand for the pigment. At present, we understand, the greater part of the carbonate of soda in the market is furnished by decomposing the sulphate of soda left after the muriatic

† Why did it not sink? Does salt swim like ice? I question the truth of this account.

acid is expelled in the usual way of manufacturing it from common salt. Various processes for this purpose were tried in France and made public by the French government, all depending on the principle of decomposing the acid of the sulphate, by charcoal, and at the same time adding some other material to prevent the soda from forming a sulphuret. What they consider as the best, is to mix the sulphate of soda with an equal weight of chalk and rather more than half its weight of charcoal powder, and to expose the mixture in a reverberatory furnace to a heat sufficient to bring them to a state of imperfect liquefaction. Much of the sulphur formed will be expelled in vapour and burned, the mixture being frequently fre stirred to promote this; and this is continued till the mass on cooling assumes a fine grain. It is then left exposed to a humid atmosphere, and the carbonate of soda may be extracted by lixiviation, the sulphur not consumed having united with the lime. Tinmen's shreds, or old iron, may be employed instead of chalk, in the proportion of 65 parts to 200 of sulphate of soda, and 62 of charcoal; or chalk and iron may be used at the same time in different proportions. The muriate of soda might be decomposed in the first instance by the sulphate of iron, instead of the sulphuric acid. The carbonate of soda thus prepared, however, is not free from sulphur, and Dizé recommends the abstraction of it by adding litharge to the lixivium in a state of ebullition, which will render the alkali pure. Oxide of manganese was substituted in the same way with equal success; and this may be used repeatedly, merely by calcining it after each time to expel the sulphur.

Mr. Accum gives the following method, as having answered extremely well in a soda manufactory in which he was employed :- Five hundred pounds of sulphate of soda, procured from the bleachers, who make a large quantity in preparing their muriatic acid from common salt, were put into an iron boiler with a sufficient quantity of soft water. Into another boiler were put 560 lbs. of good American potash, or 570, if the potash were indifferent, dissolved in about 30 pails of water, or as little as possible. When both were brought to boil, the solution of potash was ladled into that of sulphate of soda, agitating the mixture, and raising the fire as quickly as possible. When the whole boiled, it was ladled into a wooden gutter, that conveyed it to a wooden cistern lined with lead near half an inch thick, in a cool place. Sticks were placed across the cistern, from which slips of sheet lead, two or three inches wide, hung down into the fluid about four inches distant from each

other. When the whole was cold, which in winter was in about three days, the fluid was drawn off, the crystalized salt was detached from the slips of lead, and the rock of salt fixed to the bottom was separated by a chisel and mallet. The salt being washed in the same cistern, to free it from impurities, was then returned to the boiler, dissolved in clear water, and evaporated till a strong pellicle formed. Letting it cool till the hand could be dipped into it, it was kept at this temperature as long as pellicles would form over the whole surface, and fall to the bottom. When no more pellicles appeared without blowing on the surface, the fire was put out, and

the solution returned into the cistern to crystallize. If the solution be suffered to cool pretty low, very little sulphate of potash will be found mixed with the soda; but the rocky masses met with in the market generally contain a pretty large quantity. In the process above described, the produce of the mixed salt from 100 lbs. of sulphate of soda was in general from 136 to 139 lbs.

Besides its use in seasoning our food, and preserving meat both for domestic consumption and during the longest voyages, and in furnishing us with the muriatic acid and soda, salt forms a glaze for coarse pottery, by being thrown into the oven where it is baked; it improves the whiteness and clearness of glass; it gives greater hardness to soap; in melting metals it preserves their surface from calcination, by defending them from the air, and is employed with advantage in some assays; it is used as a mordant, and for improving certain colours, and enters more or less into many other processes of the

arts.

The muriate of strontian has not long been known. Dr. Hope first distinguished it from muriate of barytes. It crystallizes in very slender hexagonal prisms, has a cool pungent taste, without the austerity of the muriate of barytes, or the bitterness of the muriate of lime; is soluble in 0.75 of water at 60°, and to almost any amount in boiling water; is likewise soluble in alcohol, and gives a blood-red colour to its flame.

It has never been found in nature, but may be prepared in the same way as the muriate of barytes.

The muriate of lime has been known by the names of marine selenite, calcareous marine salt, muria, and fixed sal ammoniac. It crystallizes in hexaedral prisms, terminated by acute pyramids; but if the solution be greatly concentrated, and exposed to a low temperature, it is condensed in confused bundles of needly crystals. Its taste is acrid, bitter, and very disagreeable. It is soluble in half its weight of cold [9]

VOL. I.

water, and by heat in its own water of crystallization. It is one of the most deliquescent salts known; and when deliquesced has been called oil of lime. It exists in nature, but neither very abundantly nor very pure. It is formed in chemical laboratories, in the decomposition of muriate of ammonia; and Homberg found, that, if it were urged by a violent heat, till it condensed, on cooling, into a vitreous mass, it emitted a phosphoric light upon being struck by any hard body, in which state it was called Homberg's phosphorus.

Hitherto it has been little used except for frigorific mixtures; and with snow it produces a very great degree of cold. Fourcroy, indeed, says he has found it of great utility in obstructions of the lymphatics, and in scrofulous affections.

The muriate of ammonia has long been known by the name of sal ammonia, or ammonic. It is found native in the neighbourhood of volcanoes, where it is sublimed sometimes nearly pure, and in different parts of Asia and Africa. A great deal is carried annually to Russia and Siberia from Bucharian Tartary; and we formerly imported large quantities from Egypt, but now manufacture it at home. See AMMONIA.

This salt is usually in the form of cakes, with a convex surface on one side, and concave on the other, from being sublimed into large globular vessels; but by solution it may be obtained in regular quadrangular crystals. It is remarkable for possessing a certain degree of ductility, so that it is not easily pulverable. It is soluble in 3t parts of water at 60°, and in little more than its own weight of boiling water. Its taste is cool, acrid, and bitterish. Its specific gravity is 1.42. It attracts moisture from the air but very slightly.

Muriate of ammonia has been more employed in medicine than it is at present. It is sometimes useful as an auxiliary to the bark in intermittents; in gargles it is beneficial, and externally it is a good discutient. In dyeing it improves or heightens different colours. In tinning and soldering it is employed to preserve the surface of the metals from oxidation. In assaying it discovers iron, and separates it from some of its combinations.

The muriate of magnesia is extremely deliquescent, soluble in an equal weight of water, and difficultly crystallizable. It dissolves also in five parts of alcohol. It is decomposable by heat, which expels its acid. Its taste is intensely bitter.

With ammonia this muriate forms a triple salt, crystallizable in little polyedrons, which separate quickly from the water, but are not very regularly formed. Its taste partakes of that of both the preceding salts. The best mode of preparing it, is by mixing a solution of 27 parts of muriate of ammonia with a solution of 73 of muriate of magnesia; but it may be formed by a semi-decomposition of either of these muriates by the base of the other. It is decomposable by heat, and requires six or seven times its weight of water to dissolve it.

Of the muriate of glucine we know but little. It appears to crystallize in very small crystals; to be decomposable by heat; and, dissolved in alcohol and diluted with water, to form a pleasant saccharine liquor.

Muriate of alumina is scarcely crystallizable, as on evaporation it assumes the state of a thick jelly. It has an acid, styptic, acrid taste. It is extremely soluble in water, and deliquescent. Fire decomposes it. It may be prepared by directly combining the muriatic acid with alumina, but the acid always remains in excess.

The muriate of zircon crystallizes in small needles, which are very soluble, attract moisture, and lose their transparency in the air. It has an austere taste, with somewhat of acrimony. It is decomposable by heat. The gallic acid precipitates from its solution, if it be free from iron, a white powder. Carbonate of ammonia, if added in excess, redissolves the precipitate it had before thrown down.

Muriate of yttria does not crystallize

when evaporated, but forms a jelly: it dries with difficulty, and deliquesces.

are

Fourcroy observes, that when siliceous stones, previously fused with potash, treated with muriatic acid, a limpid solution is formed, which may be reduced to a transparent jelly by slow evaporation. But a boiling heat decomposes the siliceous muriate, and the earth is deposited. The solution is always acid.

* ACID (MURIATIC, OXYGENATED). See

CHLORINE.*

* ACID (MURIATIC, OXYGENIZED). This supposed acid was lately described by M. Thenard. He saturated common muriatic acid of moderate strength with deutoxide of barium, reduced into a soft paste by trituration with water. He then precipitated the barytes from the liquid, by adding the requisite quantity of sulphuric acid. He next took this oxygenized muriatic acid, and treated it with deutoxide of barium and sulphuric acid, to oxygenate it anew. In this way he charged it with oxygen as often as 15 times. He thus ob tained a liquid acid which contained 32 times its volume of oxygen at the temperature of 68° Fahr. and at the ordinary atmospherical pressure, and only 44 times its volume of muriatic acid, which gives about 28 equivalent primes of oxygen to

1

one of muriatic acid. For the ratio of oxygen to the acid, by weight, is 1. to 4.6; but by measure the ratio will be as these two numbers respectively divided by the specific gravity of the gases, or as T.TT tog, which by reduction makes near ly one volume of oxygen, equivalent to four of muriatic acid. Now, the oxygen in the above result, instead of being 1-4th of the volume of the acid gas, was seven times greater, whence we derive the number 28. Still more oxygen may however be added. On putting the above oxygenized acid in contact with sulphate of silver, an insoluble chloride of this metal subsides, and the liquid is oxygenized sulphuric acid. When this is passed through the filter, muriatic acid is added to it, but in smaller quantity than existed in the original oxygenized acid. A quantity of barytes, just sufficient to precipitate the sulphuric acid, is then added. Instantly the oxygen, leaving the sulphuric acid to unite with the muriatic acid, brings that acid to the highest point of oxygenation. Thus we see that we can transfer the whole of the oxygen from one of these acids to the other; and on a little reflection it will be evident, that to obtain sulphuric acid in the highest degree of oxygenation, it will be merely necessary to pour barytes water into oxygenated sulphuric acid, so as to precipitate only a part of the acid.

All these operations, with a little practice, may be performed without the least difficulty. By combining the two methods just described, M. Thenard found that he could obtain oxygenized muriatic acid, containing nearly 16 times as many volumes of oxygen as of muriatic acid, which represents about 64 equivalent primes of the former to one of the latter. This oxygenized acid leaves no residuum when evaporated. It is a very acid, colourless liquid, almost destitute of smell, and powerfully reddens turnsole. When boiled for some time, its oxygen is expelled. It dissolves zinc without effervescence. Its action on the oxide of silver is curious. These two bodies occasion as lively an effervescence as if an acid were poured upon a carbonate. Water and a chloride are formed, while the oxygen is evolved. This oxide enables us to determine the quantity of oxygen present in the oxygenized acid. Pour mercury into a graduated glass tube, leaving a small determinate space, which must be filled with the above acid, invert the tube in mercury, let up oxide of silver diffused in water; instantly the oxygen is separated.

We ought, however, to regard this apparent oxygenation of the acid, merely as the conversion of a portion of its com

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