Arsenic, an heavy, opaque, crystalline substance, which, on fracture, resembles sal ammoniac in a concrete state. Most of the metallic ores contain it in greater or less proportion, especially those of copper, tin, bismuth, and the fossil called cobalt, from which last it is extracted in Saxony, by a kind of sublimation. Its true nature is so little known, that chemists have hesitated whether it ought to be ranked among the salts, or semi-metals ; because it may, by various processes, be made to assume either a saline or metal-lie state. Hence, it has by many been considered as a mineralizing substance, which only tends to combine metals, and to give them a more perfect form. Nay, there are others, who have doubted whether it be a simple bo .ly ; and welll remember the assertion of an ingenious lecturer on chemistry and pharmacy in Edinburgh, who 6tili flatters himself with the hope of being able, at some future period, to demonstrate by experiment, ."that arsenic is the true basis of silver."

This semi-metallic concrete is very usefully employed in various branches of the arts and manufactures ; it is frequently added as an ingredient, to facilitate the fusion of glass, and to produce a certain degree of opacity. Painters use two arsenical preparations, namely, the orpiment and realgar. A beautiful green pigment may be precipitated from blue vitriol, by a watery solution of white arsenic and vegetable alkali : this, when prepared either with water or oil, affords a permanent colour. It is highly probable that, if arsenic were added to the paint used for wood, it might form an ingredient which would not be liable to be preyed upon by worms. But the practice of painting the toys of children with arsenical pigments, deserves severe censure ; as they are accustomed to put every thing into their mouth.

In dyeing, it is likewise of great service. Combined with sulphur, it has the property of readily dissolving indigo ; for which purpose it is used in the printing of calico, and other cloth. On exposure to the air, however, the arsenic is precipitated from this solution, and may be farther employed in pencil colours. Some dyers are said to understand the art of imparting beautiful shades of colours to furs, by arsenical solutions.

In rural and domestic economy, this concrete is also frequently re-sorted to with great advantage, though not always with due precaution. Farmers dissolve it in lime-water, for steeping wheat, in order to prevent the smut; and it is likewise asserted, that the husbandmen of Flanders and Germany use it for fertilizing the earth, by sprinkling the soil with a solution of arsenic in dung-water.

In medicine, it has long been known as the basis of the most celebrated cancer-powders, especially those of Plunket, Dr. Hugh Martin, and probably also, of Guy's. A weak solution of it in water, is directed by Dr. Way, of Wilmington, for effectually cleansing foul ulcers, and removing impurities of the skin : it is prepared by boiling one ounce of white arsenic in two quarts of water to three pints, and applying it once or twice a day. When it is used for extracting, or discussing, cancerous or schirrous tumors, that are not ulcerated, the above-mentioned Dr. Martin, a late physician in America, previously ordered a blister of Spanish flies to be applied to the part, with a view to open the pores of" the skin. But, as he prescribed it empirically, and indiscriminately in all cancerous cases, we were not surprized to learn from his old professor, Dr. Benj. Rush, one of the most candid and enlightened American practitioners, that his pupil has often been unsuccessful in the application of his arsenicated powder.

In the cure of agues, a solution of this mineral has been strongly recommended, and administered with it is presumed, that the liquid medicines, now secretly exhibited by a physician in the metropolis, who positively maintains that be cures cancer: " by absorption, " likewise consist with successs, upon the authority of* Drs. Fowler, ArNold, Wi-theringg, Willan, Maksh, Fear-Son, and many other respectable English and foreign pra6titioners, who do not hesitate to prescribe it in closes, from two to twelve drops, once, twice, or oftener in the courseon of the day, according to the age, strength, and other circumstances of the patient.

A preparation similar to that directed by Dr. Fowler, and called the white tasteless ague-drop, has lately been given with singular efficacy in the hooping-cough. We relate this fact upon the evidence of Mr. CorP, an eminent surgeon, of Barnet.

Notwithstanding these remark-able and powerful effects of arsenic over the virulence of diseases, which appear to depend either on a specific contagious miasma, such as is 'supposed to produce the ague and hooping-cough, or on a peculiar disposition of the fluids and solids, to undergo a certain degree of decomposition in the iiving body, as is evident in cancers, and other malignant ulcers, —we are, on the -combined testimony of many 'medical practitioners, equally celebrated for their extensive practice and erudition, as they are conspicuous for their professional zeal and integrity, irresistibly induced to declare our opinion, at least, against the internal use of this active and dangerous medicine. Of the numerous authorities which might be adduced in support of this declaration, we shall here avail ourselves only of the conclusive testimony of Dr. Black, the late professor of chemistry in the university of Edinburgh, who maintains, that he has seen the internal exhibition of arsenic attended with fatal effects, such as hectics, tot. ; nay, he declares, that though the external application of this substance has, in some cases, proved successful, it has often, even in this way, produced dreadful consequences ; so that, far from recommending it internally, he reprobates even the external use of this precarious drug. Hence we hope to be forgiven by those worthy medical practitioners, from whom no slight motives would induce us to differ: and unless it could be proved by a plurality of cases, that patients after the taking of arsenic to some extent, have not only recovered from agues, cancers, hooping-cough, etc. but that they have likewise attained to a considerable age, without ever having been subject to paralytic, spasmodic, or phthisical disorders, we shall not be disposed to retract our opinion of its virulent and destructive tendency. Although we have deprecated the internal use of arsenic, both from the concurrent evidence of many other practitioners, and our own experience, yet we shall attempt to prove, that there is actually less danger to be apprehended from those accidents, when this corrosive poison has, by mistake, been swallowed, either in the form of a powder, or solution. And as it is frequently used for destroying rats, mice, and other troublesome animals ; for preparing sympathetic inks*, as well as for chemical tests ; to discover the adulterations of solutions made of this virulent semi-metal. We trust, however, that previous to the publication of the third or fourth Number of cur Work, we shall, by an accurate che-mica! analysis, be enabled to ascertain the truth or falsity of that assertion.—See Cancer. * See the article Sympathestic

Of of wines *, which have been sweetened by sugar of lead ; we cannot be too minute in laying down proper rales and directions for obviating the dangerous effects of such casualties, as but too often occur among those who employ arsenical preparations, in a dry or liquid state, either for gratifying their curiosity by different experiments, or for other more useful purposes.

Arsenic is one of the most sudden and violent poisons we are acquainted with. Its fumes are so deleterious to the lungs, that the artist ought to be on his guard, to prevent the:r inhalation by the mouth; for if they be mixed and swallowed with the saliva, effects will take place similar to those, Which follow its introduction into the stomach in a saline or dissolved state namely, a sensation of a piercing, gnawing, and burning kind, accompanied with an acute pain in the stomach and intestines, which last are violently contorted : convulsive vomiting ; insatiable thirst, from the parched and rough state of the tongue and throat; hiccough, palpitation of the heart, and a deadly oppression of the whole breast succeed next ; the matters ejected by the mouth, as well as the stools, exhibit a black, fetid and putrid appearance; at length, with the mortification of the bowels, the pain subsides, and the fetal catastrophe terminates the sufferings of the patient. There are, however, cases on medical record, in which, on dissection, neither the stomach nor bowels, according to the testimonies of Drs. Metzger and Hahnemann, have been corroded, nor even injured; so that tills poison may, in some instances, exert its action imme-diately on the living principle. Thus we rind, in a case related by our late friend, Dr. Unzer, of Hamburgh, that a lady, who had only tasted a little arsenic, without swallowing a particle, was twelve hours after the accident thrown into the most convulsive spasms, and attacked with inflamma pustules, not unlike the 1 covering her face, neck, and whole body, so that she recovered with great difficulty, and remained for several years in a miserable state of languor, and general debility.

For these obvious reasons, artists exposed to the fumes or vapour of this volatile mineral, ought to be extremely cautious to preserve themselves from its influence on their mouth and nostrils, as well as from touching it with their hand-, for every external contact: may be attended with serious consequences. Hence they should dress in thick and firm clothes, keep at a pi distance from the exhaling fumes, and cover the orifices of the face with a mask, made for the purpose. In their system of diet, we advise them to make use of a great proportion of bland and mucilaginous nourishment; such as fresh butter, pork, sweet oil, milk, artichokes, and similar vegetables.

With respect to the treatment of persons, after the inhalation, or swallowing" of arsenic, we shall arrange the subject under three distinct propositions.

I. When a large portion of arsenic has been introduced into the stomach, or inhaled by the lungs:

1. Immediately after the accident, brisk emetics ; for instance, half a dram of white vitriol, and, after it, plenty of sweet lintseed, or almond-oil, either of which is preferable to olive-oil; or, if these be not at hand, large draughts of milk, barley gruel, or warmed beer, with a third part of oil, or butter, ought to be substituted, as soon as possible. To facilitate the operation, a strong feather should be dipt in oil, for stimulating the tonsils. If the throat be swollen and contracted, a surgeon ought to be instantly procured, for opening the gullet by means of a probe, or other proper instruments.

2. To neutralize and deprive this corrosive poison of its activity, according to Dr. Hahnemann, nothing is more efficacious than a solution of white soap in hot water, in the proportion of half a pound of the former to a quart of the latter, which must be boiled, and the soap agitated, till the whole is dissolved; when it may be sweetened with sugar. This preparation ought to be taken without delay, and so frequently as to repeat half a tea-cup full of it every five minutes, that the patient may swallow several pounds in the course of two hours. If hepatised water (prepared by pouring acids on the liver of sulphur, and saturating, with the ascending vapours, water contained in another vessel), could be readily procured, it would, with the addition of one half of thick cream, be an excellent substitute for the solution of soap.

3. To promote the evacuation of the poison by stool, clysters composed of the preceding liquids, and a third part of castor-oil, ought to be administered, and the whole abdomen fomented with soap-water.

4. With a view to prevent local or general inflammation, beside the fomentations, cataplasms, luke-warm baths and clysters, it will, perhaps, be necessary to bleed the patient largely, but not without consulting medical men.

II. When a person has hen slowly poisoned, or has swallowed only a smalt portion of arsenic; or, if the proper remedies should have been neglecled for several hours.

In these cases, the judicious practitioner only can decide upon the relative propriety and expediency of the preceding remedies ; but if a considerable time has elapsed since the accident happened, it will be necessary to commence the treatment with purgative remedies, such as will at the same time lubricate the coats of the stomach, and the whole intestinal canal, while they tend to assuage the acrimony, and counteract the corrosive effect produced on the first passages. Of this nature is, in a pre-eminent degree, the castor-oil, combined with large draughts, either of the hepatised or soap-waters. A strictly antiphlogistic regimen ought now to be pursued, together with the remedies proper to obviate inflammation, and afterwards a milk-diet, lintseed tea, barley-water, gruel, and infusions of different mucilaginous vegetables, milk-chocolate without spice, aided by the enjoyment of fresh and pure air.

III. Indications of cure, when the patient labours under a gradual and long-continued action of the poison ; or in the secondary stages of the two former casualties.

The principal object now to be attained, is the destru6tion of poisonous matter in the second pasor to prevent its influence on the kidneys, biliary ducts, tlie organs of perspiration, etc. To ascertain whether the virus has diffused itself through the system, the person's state of mind and body-should be comparatively examined; whether the former be dejected, or the latter reduced to preternatural debility; or whether any of the animal and natural functions be impaired. When there appears a blue ring round the eyes, and the lips exhibit a similar colour, we may conclude, that the devastation occasioned in the whole frame is considerable : and in such instances, Dr. Boerhaave advises to let the patient drink no less than twelve pints of luke-warm honey-water, in 24 hours, for 3 days successively ; and to administer frequent clysters of the same liquid. By this simple treatment, he observes, all those painful and dangerous symptoms, which sometimes afflict the victims of this poison through the remainder of their lives, have been effectually obviated. On the contrary, M.Navier, a reputed French writer, on the effects of arsenic and its antidotes, recommends the method we have already pointed out, in propositions I. and II.; after which, he insinuates the propriety of re-commencing a milk-diet, and enjoins the patient to abstain from the use of all acid sub-stances, or liquors. In this opinion he is likewise supported by Dr. Hahnemann, who cautions the convalescent to be very attentive to his evacuations by stool: which, so long as he is subject to griping pain, and strictures in the abdomen, constantly require to be aided by the mildest purgatives. Beside these, he may drin:. decoctions of the Lichen islandicus, of the root called Poly gala senega, or of quassia-wood, which last is, of all other corroborant and astringent remedies, the least heating, and consequently the most proper.

In order to prevent all the bad consequence:- resulting from this malignant poison, the patient may with advantage resort to the warm mineral, sulphureous waters, which he should not only drink plentifully, but likewise bathe in them, especially in the form of vapour. If such natural waters cannot be easily procured, they may be artificially substituted by medical men, who are, in general, perfectly well acquainted with their component parts, as well as the manner of preparing them. By their proper use, the unfortunate invalid may at length recover from that tremu-lating affection of the limbs, relaxation, paralysis, convulsions, and other distressing complaints, , which the improvident swallowing of arsenic usually produces.

From a multiplicity of instances related by "Wepier, Heer, Zitt-man, Ebell, and other writers, we have reason to conclude, that in our daily victuals, as well as by the use of glazed vessels, considerable portions of lead and arsenic are taken into the stomach, and mixed with solid food; though unattended with danger or inconvenience, except that of vomiting. Sometimes, however, where the digestive organs are in a languid state, the poison may lodge in the cellular membranes of the stomach and bowels, for several days or weeks, before it be evacuated. In such cases, the necessary consequence will be a slow hectic fever, for which the physician, who is generally consulted in the secondary stage of the disease, can assign no cause.

Lastly, we shall briefly mention, by what means and processes it may, after death, be discovered, whether a person have died from poison of arsenic, though this knowledge properly belongs to the department of medical police or jurisprudence.

1. The contents of the stomach and intestines should be taken out, and washed in water. If any powder be contained therein, it should be allowed to separate ; and if this be arsenic, it will fall to the bottom.

2. Place the separated powder on a red hot iron ; and, if it evaporate in a thick white vapour, without melting, there is reason to conclude that it is arsenic:— this effect will take place with the fortieth part of a grain.

3. If this powder be mixed with charcoal, and emit an odour tabling that of garlic, we may also infer that it is arsenic.

4. The most convincing test of its nature is the following: in-close the mixed powder with the charcoal, between two small polished plates of copper (or between two perfectly smooth halfpenny-pieces), the edges of which must be cemented with a lute made of two parts of tine sand, and one of pipe-clay. Fasten the plat:s with a thin wire, and expose the whole to a red heat: thus the arsenical powder will be metallized ; and, penetrating the copper, a blackish skin will first appear upon it, which being rubbed off", the parts touched by the arsenical vapour will acquire a whitish or leaden colour.

A. this deleterious concrete fre-. quently enters metallic compositions, especially those of copper and tin, it were much to be wished, that such compound metals could for ever be banished, at least from our kitchens. - See Copper, LEAD, PEWTER, and Tin.