Sublimate of mercury

Mercuric Chloride. Mercuric c Aon.d.e.[7487-94-7] HgCl2, is also known as corrosive sublimate of mercury or mercury bichloride. It is extremely poisonous, and is particularly dangerous because of high (7 g/L at 25°C) water solubiUty and high vapor pressure. It sublimes without decomposition at 300°C, and has a vapor pressure of 13 Pa (0.1 mm Hg) at 100°C, and 400 Pa (3 mm Hg) at 150°C. The vapor density is high (9.8 g/cm ), and therefore mercuric chloride vapor dissipates slowly (5). 

As it turns out, the fourth chapter of Albertus opusculum hermeticum happens to deal with the subject of The Sublimation of Mercury, and it also happens to make repeated mention of the pseudo-milk-chocolate, or faeces, encountered in the initial phases of an alchemical operation. It reads as follows ... 

The decomposition of mercuric oxide by heat has already been mentioned as the method by which Priestley was led to the discovery of oxygen. The oxide, which is yellow or brick red m colour, first becomes black—a reversible, physical effect. Oxygen is then evolved and a sublimate of mercury collects on the cooler parts of the containing vessel. The reaction is reversible, thus ... 

The Countess of Essex, still consumed by hate for Thomas Overbury, plotted to kill him. She procured the help of an apothecary named Eranklin. Eranklin supplied poisons, including rosalger (a compound of arsenic), sublimate of mercury and white arsenic, to Weston, the under-keeper of the Tower. Weston, under heavy bribery from the Countess, mixed small quantities of poison into Overbury s food over the course of 4 months. Overbury became very unwell and eventually died. At first his death was thought to be the result of syphilis, but after some time, suspicion was aroused and the case was brought to trial. 

Butter of antimony (antimony(III) chloride), for example, which was used as a caustic agent to treat ulcers, was produced by Glauber in the middle of the seventeenth century by dissolving antimony oxide in hydrochloric acid and by distilling off the salt, which was an oily fluid. Or, sublimate (mercury(II) chloride) was a volatile substance obtained from the sublimation of mercury together with common salt and vitriol. Spiritus fumans Libavii (tin(IV) chloride), a smoky liquid, was also distilled from a mixture of tin with sublimate. 

Mercury compounds of all varieties when heated to dull red heat leave no residue or this contains no mercury. This behavior, which is unique among metal compounds, is due to the sublimation of mercury salts and to thermal decomposition with production of mercury vapor. The latter can be detected by the sensitive test with palladium chloride in which the reaction PdCla + HgO Pdo -f- HgCl ... 

Boiling point is given at atmospheric pressure (760 mm of mercury or 101 325 Pa) unless otherwise indicated thus 82 indicates that the boiling point is 82°C when the pressure is 15 mm of mercury. Also, subl 550 indicates that the compound sublimes at 550°C. Occasionally decomposition products are mentioned. 

Many mercury compounds are labile and easily decomposed by light, heat, and reducing agents. In the presence of organic compounds of weak reducing activity, such as amines (qv), aldehydes (qv), and ketones (qv), compounds of lower oxidation state and mercury metal are often formed. Only a few mercury compounds, eg, mercuric bromide/77< 5 7-/7, mercurous chloride, mercuric s A ide[1344-48-5] and mercurous iodide [15385-57-6] are volatile and capable of purification by sublimation. This innate lack of stabiUty in mercury compounds makes the recovery of mercury from various wastes that accumulate with the production of compounds of economic and commercial importance relatively easy (see Recycling). 

If the pump is a filter pump off a high-pressure water supply, its performance will be limited by the temperature of the water because the vapour pressure of water at 10°, 15°, 20° and 25° is 9.2, 12.8, 17.5 and 23.8 mm Hg respectively. The pressure can be measured with an ordinary manometer. For vacuums in the range lO" mm Hg to 10 mm Hg, rotary mechanical pumps (oil pumps) are used and the pressure can be measured with a Vacustat McLeod type gauge. If still higher vacuums are required, for example for high vacuum sublimations, a mercury diffusion pump is suitable. Such a pump can provide a vacuum up to 10" mm Hg. For better efficiencies, the pump can be backed up by a mechanical pump. In all cases, the mercury pump is connected to the distillation apparatus through several traps to remove mercury vapours. These traps may operate by chemical action, for example the use of sodium hydroxide pellets to react with acids, or by condensation, in which case empty tubes cooled in solid carbon dioxide-ethanol or liquid nitrogen (contained in wide-mouthed Dewar flasks) are used. 

Solid-state (topochemical) polymerization of cyclic disulfur dinitride to poly(sulfur nitride) (or polythiazyl), -fSN, occurs on standing at ambient temperature or higher [Banister and Gorrell, 1998 Labes et al., 1979 Ray, 1978]. Disulfur dinitride is obtained by sublimation of tetrasulfur tetranitride. Polythiazyl is a potentially useful material, since it behaves like a metal. It has an electrical conductivity at room temperature about the same order of magnitude as a metal like mercury and is a superconductor at 0.3°C. Polythiazyl also has high light reflectivity and good thermal conductivity. However, it is insoluble and infusible, which prevents its practical utilization. 

The product decomposes on sublimation forming mercury(ll) chloride, ammonia, and nitrogen. However, in the presence of ammonium chloride, the same reaction with ammonia with HgCb in aqueous solution yields fusible white precipitate, (NH3)2HgCl2. Similar product also is obtained by reaction of gaseous ammonia with solid mercury(II) chloride. However, the solid mer-cury(II) chloride is more stable than the above infusible product and can be melted without decomposition. 

Now build up the fire in such a way that the white mercurial matter gets carried away above the faeces [enphasis added] and so that goes up into the aludel. Four hours later, bum some more wood to get a blazing fire now both the base of the vessel and the residue within it must turn red. Continue in this manner until there remains just a bit of white mercurial substance adhering to the faeces. Now the force and violence of the fire will finally separate the parts. Mark well how by this operation you will have removed two impurities from Mercury. First, you will have taken from it all its superfluous humidity second, you will have ridded it of its impure earthy parts, those that were left in the faeces. In this way you will have sublimated the mercury into a bright-colored and half-fixed substance. ... 

The mercury of commerce, which usually is contaminated with variable portions of lead, tin, and bismuth, may be distilled with one-tenth of its weight of cinnabar and provided the distillation be carefully effected, the foreigu impurities will he found in the retort, in the form of sulphides, after tho pure mercury has passed over into the receiver. A purer product is, however, obtained when carefully prepared cinnabar or corrosive sublimate—chloride of mercury —that has been cautiously sublimed, is distilled with one part of quicklime or iron filings. The principal part of the impu-... 

It is stated that protoxide of mercury ia occasionally adulterated -with minium or red lead, sesquioxide of iron, and powdered brick. Such substances are readily detected by heating the substance to a dull heat the protoxide of meroury sublimes, and leaves the nonvolatile matters in the crucible, or the mercurial compound maybe treated with dilute nitric add, to dissolve the mercurial oxide and should minium be present, a pace-colored binoxide of lead remains together with the other adulterants, if any be present. On adding dilute sulphuric acid to the door liquor obtained in the foregoing, a white precipitate of sulphate of lead falls, corroborative of the existence of a lead compound. 

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