Melting mercury compounds

Alkali-mctal-mercury compounds decompose rapidly in O2 or moisture and must be prepared in melt atmospheres or under vacuum. To prepare NaHg, NaHgj and Na,Hg2, known amounts of Hg and Na are flushed with N2. The reaction is exothermic, and mixing is carried out slowly, homogeneity being achieved by shaking. An excess of Na or Hg is necessary for crystal formation. ... 

The colorless zinc compound, Zn(CisH6)2, which sublimes at 160° under partial decomposition, is obtained in small yield from zinc chloride and cyclopentadienyl sodium in diethyl ether however, the less stable cadmium compound decomposes, with separation of cadmium, under these conditions (55). The mercury compound, Hg(CsH5)2, is produced in 20% yield by the action of the sodium derivative on mercuric chloride in tetrahydrofuran (215). The action of cyclopentadiene on the complex K2(HgI ) in aqueous alkaline solution results in the precipitation of a mixture of CsHsHgl and Hg(CsH6)2, from which the latter compound may be obtained in good yield by extraction with a mixture of tetrahydrofuran and petroleum ether (62). It forms pale yellow crystals which begin to decompose at about 60° and which melt at 83-85°. The compound is readily soluble in most solvents it decomposes slowly even when kept in the dark at room temperature it is insoluble in water and reacts with neither water nor bases. On the other hand, decomposition occurs in dilute hydrochloric acid. It converts ferric chloride to ferrocene quantitatively, and it yields an adduct with maleic anhydride (215). 

The latter is prepared by suspending 2 grams of powdered tetra-aeetoxy-mercuri compound in about 40 c.c. of a quarter Normal hydrochloric acid, and shaldng on a machine for twelve liours. It is filtered and washed free from chloride and dried in mcuo over phosphorus pentoxide at lOO C. The substance is a micro-crystalline powder, slightly soluble in acetone, but insoluble in all other solvents. It does not melt, and is not immediately blackened by ammonium suiphide. 

This compound is prepared as the preceding one, from 5-chloro-l-]>henyl-3-methyipyrazole. It melts at 123 C., is readily soluble in water, aleoliol, and all the usual solvents. It is unaffected l)y cold ammonium sulphide, but with hydrochloric acid yields a dichloro-mercuri compound, needles, M.pt. lOo C. 

Indium diphenyl chloride.—Indium trichloride Irom 1-lC grams of metallic indium, and 10-77 grams of mercury diphenyl (3 mols.) are boiled with 50 c.c, of xylene for thirty-seven hours. After filtering, the residue mostly melts at 245" to 250 " C., but a portion does not melt at 295° C. The mass is extracted in a Soxhiet apparatus with dr benzene to remove any mercury compounds, and the residue in the thimble (0 647gram) is organic and found to be indium diphenyl chloride. It is a crystalline, cream-coloured powder, insoluble in the usual organic solvents, and does not melt at 350° C. 

Ammonium amalgam (NH4Hgn) [7] is at room temperature a rather unstable compound, which decomposes to ammonia, hydrogen, and mercury, but at temperatures (—40 C) below the melting point of mercury the ammonium mercury may be stable for several minutes the ammonium mercury has properties akin to the quaternary ammonium mercury compounds (R4N (Hg5) ). 

The transition elements can be found by finding the periods (rows) from 4 to 7 under the groups (columns) 3-12. They are metals that do not show a range of properties as you move across the chart. They are hard and have high melting points. Compounds of these elements are colorful, such as silver, gold, and mercury. 

Table 14.2 shows that all three elements have remarkably low melting points and boiling points—an indication of the weak metallic bonding, especially notable in mercury. The low heat of atomisation of the latter element compensates to some extent its higher ionisation energies, so that, in practice, all the elements of this group can form cations in aqueous solution or in hydrated salts anhydrous mercuryfll) compounds are generally covalent. 

The white precipitate which forms is filtered and dried at 80°C, yielding 45 g of chloro-mercuri acid (= 89% of the theory), MP 106° to 109°C (decomp.). This compound is finally obtained in analytically pure form and with a constant melting point by two recrystallizations from acetone-water giving a MP of 131° to 132°C with decomposition. 

Wc have seen that molecular substances tend to have low melting points, while network, ionic, and metallic substances tend to have high melting points. Therefore, with a few exceptions, such as mercury, a substance that is liquid at room temperature is likely to he a molecular substance. Liquid solvents are heavily used in industry to extract substances from natural products and ro promote the synthesis of desired compounds. Because many of these solvents have high vapor pressures and so give off hazardous fumes, luinids that have low vapor pressures hut dissolve... 

It explodes without melting when heated [1]. The title compound and its barium, lead(II), and mercury(II) salts were studied by DTA and DSC techniques. The lead salt is the least stable and most powerful primary explosive of the 4 compounds [2],... 

---