SECTION IV.

OF MERCURY.

Experiment 1. If two parts of red sulphuret of mercury (cinnabar) reduced to powder and mixed with one of iron filings, be put into a stone retort, the neck of which is then introduced into a receiver filled with water, and heat applied until the retort is of a red colour, mercury will come over.

Rationale. The sulphuret of mercury is decomposed by the iron filings; the sulphur combines with the iron, forming a sulphuret of iron, and the mercury is disengaged, which is then volatilized, and condensed in the receiver.

Experiment 2. If to a solution of corrosive muriate of mercury, ammonia be added, and the precipitate thus obtained heated in a retort by itself, or mixed with oil, mercury will be obtained.

Rationale. The ammonia unites with the muriatic acid of the muriate, forming muriate of ammonia, at the same time an oxyd of mercury is precipitated. The oxyd when exposed to heat is decomposed, and the mercury is obtained pure.

Remark. Mercurial ores, if they be sulphurets, are best analyzed by distilling a mixture of three parts of the ore and one of lime, or iron filings, in a strong red heat, in the manner stated in Experiment 1. For the different modes of examining mercurial ores, consult Klaproth's Analytical Essays. The different ores of this metal are enumerated in the table of the classification of ores The colour of mercury is similar to that of silver. It is also known by the names of hydragyrum, argentum vivum and quicksilver. Its specific gravity is 13.568. In a solid state, which is effected by artificial means, its density is increased; its specific gravity being about 14.4 Mercury may be rendered solid, according to

Mr. Pepys, who froze 56lbs. of it, in the following

manner:

Experiment 3. Into a mixture consisting of muriate of lime, 2lbs. at + 33°, and the same weight of snow at + 32°, which will produce a cold equal to 42°, introduce a bladder containing the mercury. When the mixture has robbed the mercury of so much of its heat, as to have its own temperature thereby raised from 42° to +5°, another mixture of the same kind and quantity is to be made, which will give with a spirit thermometer 43°. If a cloth be used, in order to suspend the bladder containing the mercury, the mercury may be received into it, and put gently into this new mixture, where it will be cooled still lower than before. Five pounds of muriate of lime, placed in a large pail made of tinned iron, is now to be placed in a cooling mixture in an earthen ware pan. The mixture in the pan, in Mr. Pepy's experiment, which consisted of 4lb. of muriate of lime, and a like quantity of snow of the same temperature as the former, in one hour reduced the 5lbs. of muriate in the pail to 15o. The mixture was then emptied out of the earthen pan, and four large corks at proper distances, placed on its bottom to serve as rests for the japanned pail,which is now put into the pan. The corks answer the purpose of insulating the inner vessel, while the external one kept off the surrounding atmosphere, and' preserved the air between the two at a low temperature.

In the experiment of Mr. Pepys, to the five pounds of muriate of lime which had been cooled, as already noticed to 15°, and which still remained in the metallic vessel, was now added snow, uncompressed and free from moisture, at the temperature of 32°. In less than three minutes it gave a temperature of — 62°; a degree of cold which was never produced before, being 949 below the freezing point of water.

The mercury by immersion in the second cooling mixture, will be reduced to about 30°, and is to be cautiously put into the last made mixture of 62;

the bladder containing the mercury, is now to be sus

pended from net-work into the mixture, but prevented from touching the vessel: in the course of an hour and a half the mercury will be completely frozen, and the temperature of the mixture will indicate about

46°.

Remark. Large pieces of mercury, thus frozen, may be kept some time in a solid state. In conducting the experiment, vessels, which are bad conductors of heat, should be used.

The temperature necessary for freezing mercury is -39°. This effect of the congelation of mercury is owing to the abstraction of caloric from that metal, which is accomplished by the freezing mixture. That mercury might be rendered cold was accidentally discovered by professor Braun at Petersburg in 1759. The experiment was afterwards repeated in England and France, and in the United States. Solid mercury may be subjected to the blows of a hammer, and may be extended without breaking. It is therefore malleable. Mercury as it occurs is always in a fluid form, because its fusibility is so great, that the ordinary temperature of the atmosphere is sufficient to preserve it in that state. At the poles, however, mercury in all probability would remain solid.

Experiment 4. If a lump of frozen mercury be dropped into a cup of warm water, it will become fluid, and the fluid water in the same instant will become solid.

Rationale. The temperature of the water is reduced by the solid mercury to 32 or below 32o, which therefore freezes, whilst the frozen mercury absorbs the caloric of the water, and becomes fluid.

Experiment 5. If mercury be exposed to the tem. perature of 65-6°, it boils, and is converted into vapour.

Remark. Mercury may, therefore, be evaporated and distilled; the vapour of which is invisible and elastic like common air. By the distillation of mercury it is purified; if it be entirely pure, no residuum is left. Mercury is not altered by water. As that fluid has the property of oxydizing some metals, with which.

mercury is sometimes contaminated, its purification has been proposed by Dr. Priestley in the following manner:

Experiment 6. Put mercury into a vial with water; shake the vial occasionally; and let the whole remain for some time. Pour off the fluid, which contains those metals in an oxydized state, and the quicksilver will remain pure.

Rationale. Water has the property of oxydizing some metals, whereas on others it has no effect, Hence, when they are thus converted into oxyds, they separate from the mercury. I have tried this method, and found it to answer; if the mercury, however, contains gold or silver, it is then only purified by distillation. Some chemists, as Wasserburg, are of opinion that the oxyd formed by the agency of water on mercury, is nothing more than the black oxyd of mercury. Experiment 7. If mercury be agitated for some time in oxygen gas, or in common air, it is converted into the black oxyd.

Remark. This oxyd, the prot oxyd, contains about 7.5 per cent. of oxygen. The black oxyd of mercury may be obtained, according to Saunders, in the following manner:

Experiment 8. Triturate submuriate of mercury with lime water, till the former is completely decomposed, and a black powder will remain.

Rationale. The muriatic acid of the muriate unites with the lime, whilst the oxyd of mercury is separated in the form of a black powder.

Remark. What is called the ash coloured oxyd of mercury in the Dispensatories, appears to be a subnitrate of mercury and ammonia. See salts of mercury.

The preparation called hydragyrum cum creta, formed by triturating quicksilver with chalk, contains mercury, according to Fourcroy, with 0.04 of oxygen. When mercury is triturated with viscid substances, as fats, honey, syrups, &c. or with pulverent substances, for the purposes of medicine, it appears to be oxydized to the minimum. The solution of mercury in nitric acid, prepared without the assistance of heat, contains

an oxyd, according to Chenevix, composed of 89.3 mercury, and 10.7 oxygen.

Experiment 9. If mercury, or its prot-oxyd, be exposed to the heat of about 600o it assumes a red colour. This oxyd is called the per oxyd; or,

Experiment 10. If mercury be introduced into a mattrass with a long neck, and placed in a sand bath heated constantly to the boiling point, its surface will become black, then red, and at last the whole will be converted into the precipitate per se.

Rationale. The mercury gradually absorbs oxygen, and forms the red oxyd. This oxyd, contains seven per cent. of oxygen.* The precipitate per se, known also by the name of calcined mercury, has been administered as a medicine.

Experiment 11. If mercury be dissolved in nitric acid, the solution evaporated to dryness, and exposed to a strong heat, it assumes a red colour.

Rationale. The oxydizement of the mercury is effected, in this instance, by the decomposition of nitric acid; nitric oxyd gas is disengaged, and the mercury combines with oxygen. This preparation, however, as it is considered a variety sub-nitrate of mercury, will be noticed under the salts of that metal.

Experiment 12. If one part of mercury and three of sulphur, be triturated in a mortar, and the mixture moistened with water until all the mercury disappears, a black powder will be obtained.

Rationale. The sulphur unites with the mercury, at the same time some moisture is decomposed, and a black hydrosulphuret of mercury, or Ethiop's mineral, is formed; or,

Experiment 13. If mercury be heated and poured upon sulphur in the state of fusion, and the mixture then stirred, a combination will be formed similar to the last experiment.

Remark. The black sulphuret prepared according to this mode, differs from the former in some of its properties.

* Fourcroy.