Mendeleev’s law See periodic
law.
mendelevium Symbol Md. A radioactive metallic transuranic element
belonging to the *actinoids; a.n. 101;
mass number of the Ürst discovered
nuclide 256 (half-life 1.3 hours). Several short-lived isotopes have now
been synthesized. The element was
Ürst identiÜed by Albert Ghiorso,
Glenn Seaborg (1912–99), and associates in 1955.
A
• Information from the WebElements site
Mendius reaction A reaction in
which an organic nitrile is reduced
by nascent hydrogen (e.g. from
sodium in ethanol) to a primary
amine:
RCN + 2H 2 → RCH 2 NH 2
menthol A white crystalline terpene alcohol, C 10 H 19 OH; r.d. 0.89;
m.p. 42°C; b.p. 103–104°C. It has a
minty taste and is found in certain
essential oils (e.g. peppermint) and
used as a Ûavouring.
mercaptans See thiols.
mercapto group See thiols.
mercuric compounds Compounds of mercury in its +2 oxidation state; e.g. mercuric chloride is
mercury(II) chloride, HgCl 2 .
mercurous compounds Compounds of mercury in its +1 oxidation state; e.g. mercury(I) chloride is
mercurous chloride, HgCl.
mercury Symbol Hg. A heavy silvery liquid metallic element belonging to the *zinc group; a.n. 80; r.a.m.
200.59; r.d. 13.55; m.p. –38.87°C; b.p.
356.58°C. The main ore is the sulphide cinnabar (HgS), which can be
decomposed to the elements. Mercury is used in thermometers,
barometers, and other scientiÜc apparatus, and in dental amalgams. The
element is less reactive than zinc and
cadmium and will not displace hydrogen from acids. It is also unusual
in forming mercury(I) compounds
containing the Hg 2
2+ ion, as well as
mercury(II) compounds containing
Hg
2+ ions. It also forms a number of
complexes and organomercury compounds.
A
• Information from the WebElements site
mercury cell A primary *voltaic
cell consisting of a zinc anode and a
cathode of mercury(II) oxide (HgO)
mixed with graphite. The electrolyte
is potassium hydroxide (KOH) saturated with zinc oxide, the overall reaction being:
Zn + HgO → ZnO + Hg
The e.m.f. is 1.35 volts and the cell
will deliver about 0.3 ampere-hour
per cm
3 .
mercury(I) chloride A white salt,
Hg 2 Cl 2 ; r.d. 7.15; sublimes at 400°C. It
is made by heating mercury(II) chloride with mercury and is used in
calomel cells (so called because the
salt was formerly called calomel) and
as a fungicide.
mercury(II) chloride A white salt,
HgCl 2 ; r.d. 5.4; m.p. 276°C; b.p.
302°C. It is made by reacting mercury with chlorine and used in making other mercury compounds.
mercury(II) fulminate A grey
crystalline solid, Hg(CNO) 2 .½H 2 O,
made by the action of nitric acid on
mercury and treating the solution
formed with ethanol. It is used as a
detonator for cartridges and can be
handled safely only under cold water.
mercury(II) oxide A yellow or red
oxide of mercury, HgO. The red form
is made by heating mercury in oxygen at 350°C; the yellow form, which
differs from the red in particle size,
is precipitated when sodium hydroxMendeleev’s law
348
m
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law.
mendelevium Symbol Md. A radioactive metallic transuranic element
belonging to the *actinoids; a.n. 101;
mass number of the Ürst discovered
nuclide 256 (half-life 1.3 hours). Several short-lived isotopes have now
been synthesized. The element was
Ürst identiÜed by Albert Ghiorso,
Glenn Seaborg (1912–99), and associates in 1955.
A
• Information from the WebElements site
Mendius reaction A reaction in
which an organic nitrile is reduced
by nascent hydrogen (e.g. from
sodium in ethanol) to a primary
amine:
RCN + 2H 2 → RCH 2 NH 2
menthol A white crystalline terpene alcohol, C 10 H 19 OH; r.d. 0.89;
m.p. 42°C; b.p. 103–104°C. It has a
minty taste and is found in certain
essential oils (e.g. peppermint) and
used as a Ûavouring.
mercaptans See thiols.
mercapto group See thiols.
mercuric compounds Compounds of mercury in its +2 oxidation state; e.g. mercuric chloride is
mercury(II) chloride, HgCl 2 .
mercurous compounds Compounds of mercury in its +1 oxidation state; e.g. mercury(I) chloride is
mercurous chloride, HgCl.
mercury Symbol Hg. A heavy silvery liquid metallic element belonging to the *zinc group; a.n. 80; r.a.m.
200.59; r.d. 13.55; m.p. –38.87°C; b.p.
356.58°C. The main ore is the sulphide cinnabar (HgS), which can be
decomposed to the elements. Mercury is used in thermometers,
barometers, and other scientiÜc apparatus, and in dental amalgams. The
element is less reactive than zinc and
cadmium and will not displace hydrogen from acids. It is also unusual
in forming mercury(I) compounds
containing the Hg 2
2+ ion, as well as
mercury(II) compounds containing
Hg
2+ ions. It also forms a number of
complexes and organomercury compounds.
A
• Information from the WebElements site
mercury cell A primary *voltaic
cell consisting of a zinc anode and a
cathode of mercury(II) oxide (HgO)
mixed with graphite. The electrolyte
is potassium hydroxide (KOH) saturated with zinc oxide, the overall reaction being:
Zn + HgO → ZnO + Hg
The e.m.f. is 1.35 volts and the cell
will deliver about 0.3 ampere-hour
per cm
3 .
mercury(I) chloride A white salt,
Hg 2 Cl 2 ; r.d. 7.15; sublimes at 400°C. It
is made by heating mercury(II) chloride with mercury and is used in
calomel cells (so called because the
salt was formerly called calomel) and
as a fungicide.
mercury(II) chloride A white salt,
HgCl 2 ; r.d. 5.4; m.p. 276°C; b.p.
302°C. It is made by reacting mercury with chlorine and used in making other mercury compounds.
mercury(II) fulminate A grey
crystalline solid, Hg(CNO) 2 .½H 2 O,
made by the action of nitric acid on
mercury and treating the solution
formed with ethanol. It is used as a
detonator for cartridges and can be
handled safely only under cold water.
mercury(II) oxide A yellow or red
oxide of mercury, HgO. The red form
is made by heating mercury in oxygen at 350°C; the yellow form, which
differs from the red in particle size,
is precipitated when sodium hydroxMendeleev’s law
348
m
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