in mineralogy and chemistry, an heavy opake substance, usually sold in white masses, which, when broken, discover a semi-transparency somewhat resembling that of sal ammoniac, but by exposure to the air become white and opake like the outside of the original mass. By various chemical processes it may Arsenic be made to assume the appearance either of an acid salt or metal, at the pleasure of the operator; and therefore has been considered both as a saline substance and as a semi-metal. It is not known at what time this mineral was discovered; though, as it abounds in many different kinds of ores, it is probable that the pernicious properties it manifests would very soon make it be taken notice of by metallurgists. Aristeus makes mention of a substance called Σαρκαστικός; and his disciple Theophrastus makes mention of one named Αρσενίκος, which by Dioscorides and others was called Αρσενίκος about the beginning of the Christian era. By this, however, it appears, that they only meant the substances now called sandarach and orpiment; and Avicenna mentioned till who lived in the 11th century, is the first who expressly mentions white arsenic, as well as its sublimate. It is not known by whom arsenic was first reduced to a metallic form. Paracelsus asserts that arsenic, sublimed with egg shell lime becomes like silver; and, in 1675, M. Lemerit makes mention of a method of subliming arsenic with fixed alkali and soap.

The true nature of arsenic being thus so little known, it is no wonder to find chemists differing very much as to the class of natural bodies in which it ought to be placed. Avicenna and a great number of others clasps it with the sulphurs; Albertus Magnus and his followers, among the salts. Becher considers it as a kind of soap, or saline sulphureous body. Later experiments, however, have made it evident, that white arsenic consists of an acid united to phlogiston; and that by diminishing the latter, the acid becomes more and more apparent; while, on the contrary, by augmenting the quantity of phlogistic matter, the arsenic affumes the metallic form. With respect to the sulphureous nature of arsenic, it appears, indeed that the regulus itself, as well as orpiment and realgar, are inflammable substances; but it is not so with white arsenic. This inflammability, therefore, which arsenic in a certain state has in common with zinc and several other substances, will not denominate it sulphureous, any more than those of other bodies which possess the common property of inflammability can be denominated sulphurs.

It is commonly said, that arsenic mineralizes metals; and therefore, says Mr Bergman, it is considered as a sulphur by some, who yet extend the idea of mineralization so far, as under it to comprehend all mixtures of which metals make a part. But if we examine this signification a little more accurately, we shall see that it is extended too far; for if this be admitted, we must at the same time allow, that no native metal is to be found. Thus the gold called native, is seldom if ever found pure, but more or less mixed with copper or silver; and so with other metals. If, therefore, arsenic, which, unless in its reguline state, never dissolves other metals, be considered as a mineralizing substance, what hinders us from saying that gold is mineralized by silver or copper, and in general every metal mineralized by some other? It is much more natural to suppose that those metals are mineralized which are actually dissolved and concealed by a menstrum. Sulphur is the chief minerizer of metals, chief agent employed by nature for this purpose; and though the acids of vitriol, phosphorus, nitre, and sometimes even the aerial acid, occasion the metals to put on an appearance foreign to their nature, yet the number of these is so small, that compared with the sulphurated minerals, they almost vanish.

This mineral, so troublesome to the mineralogist, occasioned the alchemists to suspect the existence of a certain arsenical principle indispensably necessary to the perfection of every metal. Even as late as 1773 a question to this purpose was proposed by the Royal Academy of Sciences at Berlin; the prize was adjudged to M. Monnet, who in his answer considered of metals arsenic as a semi-metal of a peculiar kind, which is so far from constituting any essential part of metals, that its presence is always attended with inconveniences, either by carrying off the metal as it flies away, or spoiling the mass in which it remains. These considerations, however, do not hinder us from asserting that the acid of arsenic, like others, is a mineralizing substance, if at any time it happens to meet with metals in the bowels of the earth, and to unite with it in that form.

Arsenic in its pure state is well known to be a most destructive and deadly poison, for which the art of medicine has scarcely as yet afforded a cure. Mr Bergman is of opinion that it acts as an highly corrosive acid, even when applied externally. He also tells us, that the dry acid is more destructive than white arsenic; the regulus and realgar less so. From an experiment of Mr Scheele, however, in which eight grains of arsenical acid were given to a cat, it does not appear that it acts more violently than white arsenic. Why it is the extreme danger attending this substance when taken into the human body, arises from its insolubility, and the difficulty of decomposing it; for there can be but little danger arise from a liquid, unless like corrosive acids, it should at once burn the substance of the stomach like fire; or, like laurel water suspend the action of the nervous system. Corrosive sublimate, solutions of mercury in aquafortis, &c. will certainly poison as arsenic; but they are much less difficult to cure, because any alkaline substance will certainly decompose them and destroy their deleterious efficacy. Arsenic, on the contrary, cannot be decomposed, nor united with any known substance, at least in such a short time as the exigence of the case we speak of would require, without a considerable degree of heat. It therefore remains in the stomach, continually exerting its mischiefous qualities, unless it can be discharged by vomiting.

The symptoms attending arsenic when swallowed are nausea, sickness, and retching to vomit, about half an hour after it is taken. These are followed by violent vomitings, hiccups, and pains in the stomach and bowels. Convulsions and palsies of the limbs presently succeed, with intense heats, cold sweats, palpitations of the heart, extreme anxiety, prostration of strength, thirst and dryness of the mouth and throat, loss of reason, and at last death. If the quantity taken was considerable, the patient dies in seven or eight hours after taking it; and the stomach and intestines are found, upon dissection, to be corroded and perforated. When this is not the case, violent putrefactive symptoms soon ensue after arsenic is swallowed; for the bodies of those who are poisoned by it generally have abundance of red or purple spots even before death. It remarkably inflames the coats of the stomach, and the putrefaction faction is said particularly to take place in the genitals of men. Mr Bergman relates, that in the body of a man who was poisoned with arsenic and dissected in the anatomical theatre at Upsal, the putrefaction had been so strong that the mineral was deprived of part of its phlogiston and emitted the garlic smell, that peculiar characteristic of arsenic when in this situation.

Many antidotes have been proposed against this dreadful poison by authors of the highest reputation; but it is to be feared without that success which the confidence of those who proposed them seemed to ensure. Indeed, previous to any great hope of success in this respect, it ought to be shown that these antidotes are able to effect some considerable change on arsenic when out of the body; and that not in solution, but when in a powder not very fine, as is the case with arsenic when it is usually taken. Mr Bergman recommends alkalies in diseases occasioned by arsenic: Nay he tells us, that "since phlogiston and alkalies are the most powerful correctors of acid acrimony, it will readily occur, how it may be mitigated, and its deleterious effects obviated." But the many fatal accidents consequent on taking this mineral, show that none of those are to be depended upon. Bergman himself indeed cautions us against trusting to phlogistic correctors alone; and perhaps the solution of hepar sulphuris, which contains the united powers of both the alkaline and phlogistic antidotes united, might prove more efficacious than either of them singly. Oils, fats, milk, warm fat broths, treacle butter, &c. have all been recommended; and, no doubt, in such deplorable cases, are those remedies to which we can most readily have recourse: but even here it is evident, that their efficacy must be exceedingly dubious, whatever their intrinsic virtues may be; and for this plain reason, that the arsenic is already in contact with the stomach, and tho' the remedies might have prevented its action had they been first swallowed, their operation must be much less powerful after the poison has had access to the stomach and begun to exert its pernicious effects.

Notwithstanding these dreadful effects of arsenic when taken in large quantity, attempts have not been wanting to introduce it into the materia medica. The disease indeed in which they have been recommended (the cancer) is of a very incurable nature, at least by ordinary medicines. M. le Febure, a French physician, some time ago published a treatise, in which he recommended pure white arsenic as a specific in that distemper. The dose was four French grains, equal to 3½ English, dissolved in a French pint (32 troy ounces) of distilled water. A table-spoonful of this solution is to be taken with an equal quantity of milk, and half an ounce of syrup of poppies, every morning fasting, and taking care to taste nothing for an hour after. This course must be continued eight days; after which a dose is to be taken twice every day in the same manner, one in the morning and another about eight at night. At the end of a fortnight three doses may be exhibited daily, the third being taken at mid-day. Thus people of a weakly constitution may continue till the cure is completed; but such as are more robust may gradually augment the dose till two table-spoonfuls are taken at each time with as much milk, and half an ounce of syrup of poppies. Children must on no account take more than three tea-spoonfuls a day, with a proportional quantity of syrup of poppies. For adults, the strength of the solution, as well as the quantity, is to be augmented; six grains being put into the second bottle and eight into the third; and a purgative, composed of manna, rhubarb, and sal feignette, is to be given every eight or twelve days. An influe he considers as useful in every case. The tumor, if not ulcerated, ought to be washed with a solution of arsenic in the proportion of eight grains to a pint; and he advises the following cataplasm: "Take of carrot juice one pound, of sugar of lead half an ounce, of arsenic, dissolved in distilled vinegar, half an ounce, of liquid laudanum a dram and an half; form the whole into a mass with as much powder of hemlock as is sufficient for the purpose. The tumor is to be covered to a moderate thickness with this cataplasm, which is to be kept on by a diachylon plaster." When the cancer is of the ulcerated kind, he directs the ichorous ferocity to be taken away by means of dry charpee at each dressing, and the sore to be fomented with the arsenical solution with the chill taken off it, and having about a third part of red wine added to it. When the sore is of a very bad kind, he proposes the arsenic to be dissolved in decoction of bark for the purpose of fomentation; after which the cataplasm and plaster are to be applied, and this is to be renewed every twelve hours.

Mr Le Febure asserts, that the arsenic, when taken with the precautions just mentioned, is not attended with any bad consequences, nor has it a disagreeable taste. Its action is scarcely perceived on any of the secretions or excretions; though some discharge their urine more freely than usual, and with some the belly is more loose. In some the perspiration is more copious; but these effects are neither regular nor constant. He does not consider it as an infallible cure for the distemper in every possible stage; but thinks that the disease is incurable, when, in its progress, it has eroded a blood-vein, and occasioned a considerable hemorrhage; also when the patient is of a hectic or phthisical habit of body. With respect to regimen, he directs whey, with twelve grains of nitre to the bottle, or a weak decoction of althea with an equal quantity of nitre; and to abstain from wine and fermented liquors. Broth made with beef, veal, or chicken, is also proper.

Mr Bergman informs us, that "it can hardly be doubted but arsenic may be applied to valuable purposes in medicine, and experiments have long ago put it, that out of doubt; but with respect both to its dose and preparation, the utmost caution is necessary."

Dr Black, however, has seen the internal exhibition of arsenic, in those cases where it is recommended by foreign physicians, attended with very dangerous consequences, such as hæmorrhages, &c. He has likewise proved known obstinate ulcers healed by it. Yet though the Dr Black external use of arsenic has proved successful in some cases, it has often, even in this way, produced very terrible consequences: so that the Doctor, far from recommending the internal use of it, reprobates it even in external applications.

As physicians are often called in cases where it is suspected that people have died from the effects of arsenic Arsenic taken internally. Doctor Black gives the following directions to the physician who happens to be thus employed.

"He should answer every question put to him with caution, as the lives and reputations of many often depend on his opinions."

"The first question usually put is, Whether, from the symptoms of the patient, or the appearance of the body after death, he imagines the deceased died by being poisoned with arsenic? The symptoms attending the taking of arsenic are, in about a quarter of an hour, sickness at stomach, succeeded by vomiting, purging, burning pain in the bowels, heat and thirst, pains and cramps in the legs and thighs, syncope, and death. When the body is examined, the intestines appear inflamed and corroded; nay, some ulcerations appear about the anus even before death. But we must take care not to be deceived by erotions of the stomach occasioned by the gastric juice, which has a power of dissolving the stomach after death. The difference is, that the arsenic occasions inflammation and blackness, whereas none appears in the other case. If the person escapes, he is in danger of being afflicted by marasmus, paralytic affections of the limbs, great debility, &c.

"The second question generally asked is, Whether any arsenic has been found in the intestines? The method of discovering this is as follows. The contents of the stomach and intestines should be taken out and washed in water; and any powder it contains suffered to separate. If any arsenic be mixed with it, it will fall to the bottom, and must then be examined by the following methods.

"1. By laying it on a red hot iron. If it be arsenic, it will evaporate, without melting, in a thick white vapour; and this may be shown by the 40th part of a grain.

"2. We may mix some of it with charcoal; in which state, if it be arsenic, it will emit an odour very like garlic; but this will not be perceived unless it be mixed with charcoal or some inflammable matter.

"3. We may inclose the powder with some charcoal, between two polished bits of copper, the edges of which are moistened with a lute made of two parts of fine sand and one of pipe clay. The plates being then bound together with a wire, and the whole made red hot, the arsenical powder will thus be metallized, and, penetrating the copper, a blackish skin will first appear upon it; which being rubbed off, the parts which the arsenical vapour has touched will appear of a whitish or lead colour.

"4. We may metallize or reduce the arsenic in a glass tube, by means of the black flux. This is easily done by mixing two or three parts of the flux with one of the powder. This mixture being put into a small glass tube, and a heat applied sufficient for volatilizing the arsenic, the greatest part of it will be metallized. One end of the tube is to be left open at first, and then stoppered with lint or wool; the other made red hot; and if the tube be then broken, the arsenic is found metallized. One grain of arsenic will be sufficient for all these experiments."

The first symptoms which ensue on the taking of arsenic show that it is of a highly inflammatory, caustic, and corrosive nature, with regard to the system in general, and the intestines in particular: the pulse becomes extremely weak and irritable, and this is attended with a kind of paralytic affection of the limbs, marasmus, &c. Milk and oil have been recommended as antidotes; but the milk may curdle, and the oil will not mix with the fluids in the intestines. It is therefore advisable, when a physician is called to a patient who has swallowed arsenic, to make use of mucilages. A friend of Dr Black's, who had no mucilage at hand, thought of the whites of eggs, and succeeded. After the violence of the first attack is over, a milk diet, opiates, &c., are proper; and some time after, electricity has been found of great service. Some have advised to exhibit hepatic sulphuris, as already noticed; but this is founded, not on experience, but theory; and it cannot be supposed that such a quantity can enter the system as will be sufficient for neutralizing the arsenic, and converting it into orpiment, which is the design of exhibiting it.

The following account of the use of arsenic in medicine is given by Dr Duncan. "Notwithstanding, however, the very violent effects of arsenic, it has been employed in the cure of diseases, both as applied externally and as taken internally. Externally, white arsenic has been chiefly employed in cases of cancer; and as used in this way, it is supposed that its good effects depend on its acting as a peculiar corrosive; and it is imagined, that arsenic is the basis of a remedy long celebrated in cancer, which, however, is still kept a secret by a family of the name of Planter in Ireland. According to the best conjectures, their application consists of the powder of some vegetables, particularly the ranunculus flammans and cotula foetida, with a considerable proportion of arsenic and flower of sulphur intimately mixed together. This powder, made into a paste with the white of an egg, is applied to the cancerous part which it is intended to corrode; and being covered with a piece of thin bladder, smeared also with the white of an egg, it is suffered to lie on from 24 to 48 hours; and afterwards the eschar is to be treated with softening digestive, as in other cases.

"Arsenic, in substance, to the extent of an eightieth of a grain for a dose, combined with a little of the flowers of sulphur, has been said to be employed internally in some very obstinate cases of cutaneous diseases, and with the best effect. But of this we have no experience.

"Of all the diseases in which white arsenic has been used internally, there is no one in which it has been so frequently and so successfully employed as in the cure of intermittent fevers. It has been long used in Lincolnshire, and some other of the fenny countries, under the name of the arsenic drop, prepared in different ways: And it is conjectured, that an article, which has had a very extensive sale, under the title of the tabelea ague-drop, the form of preparing which, however, is still kept a secret, is nothing else but a solution of arsenic. But whether this be the case or not, we have now the most satisfactory information concerning this article in the 'Medical Reports, of the effects of Arsenic in the cure of agues, remitting fevers, and periodic headaches,' by Dr Fowler of Stafford. He directs, that 64 grains of arsenic, reduced to a very fine powder, and mixed with as much fixed vegetable alkaline salt, should be added to half a pound of distilled water in a Florence flask; that it should be then placed in a sand-heat." heat, and gently boiled till the arsenic be completely dissolved; that after the solution is cold, half an ounce of compound spirit of lavender be added to it, and as much distilled water as to make the whole solution amount to a pound. This solution is taken in doses, regulated according to the age, strength, and other circumstances of the patient from two to twelve drops, once, twice, or oftener in the course of the day. And in the diseases mentioned above, particularly in intermittents, it has been found to be a safe and very efficacious remedy, both by Dr. Fowler and by other practitioners: but in some instances, even when given in very small doses, we have found it excite violent vomiting. But besides this, it has also been alleged by some, that those cured of intermittents by arsenic are very liable to become phthisical. If arsenic shall ever be extensively employed internally, it will probably be most certain and most safe in its operation when brought to the state of a salt readily soluble in water.

With regard to its other uses he expresses himself thus: "Philosophers are wont to evince the extraordinary porosity of bodies, and the wonderful subtilty of vapours, by a sympathetic ink made with orpiment and lime; for writing made with vinegar of litharge, by itself invisible, exposed to the vapour of this liquor becomes in a few minutes brown, even though a great many folds of paper be interposed.

"Wines naturally acid, or grown so by age, still continue to be edulcorated by lead, notwithstanding the punishments attending the detection of this fraud: it is therefore of great consequence to be in possession of an easy method of discovering such a sophistication. For this purpose a probatory liquor has been recommended, composed of caustic fixed alkali and orpiment; which instantly throws down a black or dark-brown precipitate in consequence of the union of the sulphur of the orpiment with the metal. The same effect will take place on the addition of common hepar sulphuris; but methods have been contrived of eluding this proof. If a small quantity of chalk be contained in the wine, the saline hepar does not produce the intended effect; for the falling of the white calcareous earth diminishes the blackness. The other probatory liquor is also rendered ineffectual by a large quantity of tartar; because the tartarous acid, uniting with the lime, forms a kind of selenite, which in like manner diminishes the blackness.

"Arsonic sometimes enters metallic compositions, especially copper and tin; but it were much to be wished that such compositions were banished, at least from the kitchen. Shot made of lead is sometimes hardened by orpiment.

"Regulus of arsenic enters into the composition of Meuder's phosphorus. The power of the calx in vitrification was long ago known to Geber; and it is frequently employed in glass houses, either for facilitating fusion, for acquiring a certain degree of opacity, or finally for carrying off phlogiston. The method in which mountain-crystals, placed over orpiment, white arsenic, crude antimony, and sal ammoniac, mixed in a crucible, are tinged by means of heat, is described by Neri, and upon trial is found to be true. I have thus obtained these crystals beautifully marked with red, yellow, and opal spots; but at the same time cracked, which could scarcely be avoided.

"In painting, too, the artists, sometimes employ arsenic. Painters in oil frequently use both orpiment and realgar; and it is probable that wood covered with a pigment mixed with white arsenic would not be spoiled by worms. A most beautiful green pigment may be precipitated from blue vitriol by means of white arsenic dissolved in water, together with vegetable alkali. This prepared either with water or oil, affords a colour which suffers no change in many years. The playthings of children, however, should not be painted with this or any other preparation of arsenic, on account of their custom of putting everything into their mouth."

Arsenic is also used in dyeing, and the yellow combination of it with sulphur has the property of readily dissolving indigo; for which purpose it is used in cloth-printing. It lets it fall again, however, on exposure to the air; and therefore can be employed only in pencil-colours, where a large quantity is laid on at once. The neutral arsenical salt is used in some manufactures in France; but for what purposes is not known.