If it contain any traces of arsenious acid, it will be shown by the bluish-white color of the flame, by the fumes of the acid, and brown shining spots of arsenic of metallic appearance will be deposited upon the porcelain plates. By heating the glass tube with a spirit lamp, metallic arsenic will be deposited in the colder part of it, forming a beautiful incrustation. The tube may be cut off at this point, the arsenic be converted into arsenious acid by heat, dissolved in hot water, and tested by the am-monio-sulphate of copper and nitrate of silver. This apparatus has been modified by Dr. Ure, so that the gas may be made at will to pass through the solutions by which the arsenic is precipitated, or to deposit the metallic incrustation in the tube, or the spots upon the plate. In its most simple form, however, it is a very useful contrivance for detecting arsenic. Antimony combined with hydrogen produces a spot that may be confounded with that of arsenic; but a solution of hypochlorite of soda instantly dissolves arsenical spots, and has no effect upon those of antimony. The arsenical spots also are volatilized at a temperature of 500° applied by a bath of olive oil, while the antimonial are unchanged.

The proper solvent for organic matters supposed to contain arsenic is a mixture of 3 parts of hydrochloric and 1 part of nitric acid, and the quantity of this should be equal in weight to the organic substance, which before being dissolved should be cut into small pieces and dried at a gentle heat. The mixture being distilled, the arsenic, if present, comes over in the form of the volatile terchloride, which is then to be converted into the tersulphuret by sulphuretted hydrogen. - Arsenious acid is manufactured on a large scale at Altenburg and Reichenstein, in Silesia, from the ore called arsenical iron. In many other places it is obtained as a secondary product in the treatment of cobalt ores, and of other metallic ores with which arsenic is associated. The process consists in roasting the ore in large muffles, 10 ft. long and 6 ft. wide, in charges of 9 or 10 cwt. each, and collecting the vapors as a sublimate upon the walls of a succession of chambers, arranged in a tower through which they pass, and from which the uncondensable gases escape by a chimney. The muffles are placed inclining upward from their mouth, and are left open for the passage of heated air to aid in subliming the arsenic and converting it all into arsenious acid.

A charge is worked off in about 12 hours, and is immediately followed by another. Charcoal is the fuel used, and as very little more heat is required than what is evolved by the chemical changes, the quantity consumed is very small. The purest arsenic is found in the flues and chambers nearest the furnace; in the upper chambers it is intermixed with the condensed sulphurous vapors. To purify it for market, it is all sublimed again. It is placed in cast-iron or porcelain pots, which hold 3 1/2 cwt. each, and these are set vertically in a furnace. They open above into sheet-iron drums, which servo as condensers, and which are connected by a funnel with the condensing chamber. The fire must be carefully regulated to maintain the proper temperature for the acid to sublime in the form of a glassy cake. If the heat is too high, metallic arsenic is apt to be sublimed and mixed with the acid, appearing in dark spots. This must be picked out, or the whole sublimed over. The preparation of arsenious acid is a most dangerous occupation. The workmen employed generally die before the age of 40; indeed, their mean term of life is stated to be only from 30 to 35 years.

Dumas states that they are compelled to avoid alcoholic drinks, and live principally upon leguminous vegetables, with plenty of butter, taking very little meat, and that very fat; and to each man two small glasses of olive oil are administered daily. In removing the acid from the chambers the workmen are completely enveloped in a dress and helmet of leather, the latter furnished with glass eyes. The passage for the air is protected with a wet sponge, by which it is filtered as it passes to the mouth and nostrils. - Arsenious acid is also found native, crystallized in octahedrons and capillary forms, at Andreasberg, in the Hartz, and at mines in Hungary and Bohemia. Combined with iron and sulphur, it forms-the common ore of arsenic, called arsenical iron, or mispickel, which is of frequent occurrence in veins of iron pyrites, and of copper, lead, silver, zinc, cobalt, nickel, and tin ores. This ore is found in many localities in Connecticut and New Hampshire particularly, but is not rare in any of the New England states, or wherever pyritous ores are found along the range of the primary rocks of the Appalachian chain. The acid is also found in the ashes of many plants; in certain soils and mineral waters; and Orfila has detected it in the earth of graveyards.

Its' diffusion in minute quantities is very remarkable. - The uses of arsenious acid are principally in medicinal preparations, such as Fowler's solution, the basis of which is the . arsenite of potash; or it may be given in substance in the dose of 1/10 of a grain, combined with something to increase its bulk. Externally, arsenious acid is used as a caustic and forms the important ingredient in many "cancer cures." It is, however, a very painful application, and in the large majority of cases this method of removing tumors possesses no advantage over the knife. It may be absorbed from the surface to which it is applied, and give rise to the usual symptoms of arsenical poisoning. Internally, it is used chiefly in skin diseases, and in malarial fevers or the cachexia arising therefrom. In these affections it displays decided efficacy. It is also used occasionally in other diseases as a tonic. The symptoms which denote that its use has been carried sufficiently far are a peculiar swelling and stiffness of the face and eyes, and some irritation of the digestive apparatus. - The statements of Von Tschudi in regard to the habitual use of arsenic by the peasants of Styria, formerly regarded as unworthy of credit, have been confirmed by subsequent observers.

Dr. C. Maclagan has published in the "Edinburgh Medical Journal " for September, 1864, an account of two cases, in one of which between four and five grains, and in the other six grains of white arsenic were taken in his presence. The urine passed by each of these men after taking the dose was analyzed, and found to contain the drug. They stated that they took a dose once or twice a week, and one of them said that the good effects lasted for eight days. They were both healthy. It is said to be given to horses to improve their wind and the smoothness of their coats. - Arsenic is sometimes chosen for criminal poisoning on account of its tastelessness. Its symptoms in the majority of cases, however, are tolerably characteristic, and it is almost sure to be detected by proper chemical tests. The symptoms and post-mortem appearances observed in the majority of fatal or severe cases are those of the most violent gastro-intestinal irritation, with proportionate depression of the circulation, intense burning pain of the stomach, obstinate vomiting, and extreme depression. In a few cases, however, death takes place rapidly by collapse, and there are no characteristic post-mortem appearances.

When a poisonous dose of arsenic has been swallowed, recourse should be had to emetics or the stomach pump, unless vomiting takes place spontaneously. Demulcent drinks may be given until the proper antidote can be procured. This is the hydrated sesquioxide of iron, which should be kept at hand in the moist condition by every apothecary. The materials for making a fresh supply, namely, a solution of some persalt of iron, for instance the persulphate or the tincture of the chloride,"and water of ammonia, should also be ready, since the oxide is most efficacious when freshly prepared. The two solutions should be mixed, and the resulting precipitate, after being rapidly filtered and washed, administered in the form of a paste. Recently precipitated magnesia has been proposed as an antidote. A mixture of chalk and castor oil is said to mechanically envelop the particles of arsenic and render them harmless. The effect of the peroxide of iron in neutralizing the action of arsenious and arsenic acids is seen in the harmless nature of the chalybeate waters of Wattwiller in Alsace, in which arsenic was found by Lassaigne to the amount of 2.8 per cent. - A milder grade of poisoning has resulted from the use of arsenical salts as pigments on wall paper or articles of millinery.