Archaic Chemical Terms

Part IV (M-R)

Go to Part I (A-B), Part II (C-F), Part III (G-L), or Part V (S-Z).

magnesia ...: magnium: Humphry Davy's name for magnesium (Mg), the metal obtained from magnesia alba, proposed to avoid confusion with the metal found in magnesia nigra.

Magnus salt: tetrammineplatinum tetrachloroplatinate, Pt(NH3)4PtCl4, named after Heinrich Gustav Magnus

malachite green: pulverized malachite, a basic copper carbonate mineral, Cu2(OH)2CO3, used as a pigment; or a green triphenylmethane dye, C23H25N2Cl, also known as Victoria green or benzal green, an acid-base indicator that changes from yellow to blue-green as the pH is raised through 1

manganese ...

Marignac salt: potassium tin(II) sulfate, K2Sn(SO4)2, named for Jean de Marignac, who is best known for atomic weight measurements

marine acid: hydrogen chloride solution, HCl (acidum salis, muriatic acid, spirit of salt). Gaseous HCl was marine acid air. [Cavendish, Lavoisier, Priestley, Scheele, et al.]

marine alkali: sodium carbonate (common mineral alkali, fossil alkali, soda)

Mariotte's law: better known today as Boyle's law, that the product of pressure and volume of a gas is constant; named for Edme Mariotte, who discovered it independently some time after Boyle

Mars: In astrological and alchemical thought, the seven heavenly bodies known to the ancients were associated with seven metals also known in antiquity. Mars was associated with iron.

marsh gas: methane, CH4

martius yellow: the calcium salt of naphthalene yellow.

massicot: a yellow lead(II) oxide, PbO.

masurium (Ma): another name proposed for technetium, element 43.[Noddack 1925]

mercurius calcinatus per se: mercuric oxide, HgO, prepared by the calcination of mercury [Priestley, Watt]. The substance known as precipitated mercury per se [Lavoisier, Priestley] or red precipitate [Priestley, Scheele] is the same substance; however, because of its different preparation (by mixing mercury with nitric acid, evaporating, and heating the residual mercuric nitrate), the identity was not at first realized.

Mercury: In astrological and alchemical thought, the seven heavenly bodies known to the ancients were associated with seven metals also known in antiquity. Mercury was associated with mercury (quicksilver, hydrargyrum).

mesothorium: There were two mesothoriums produced in thorium decay. Mesothorium I is an isotope of radium, namely 228Ra (half-life = 5.8 y); mesothorium II is an isotope of actinium, namely 228Ac (half-life = 6 hr). See table. [Hahn, Soddy 1 & 2]

metanil yellow: the sodium salt of 4'-aniline azobenzenesulfonic acid, C12H10N3O3SNa, an acid-base indicator that changes from red to yellow as the pH is raised through 1.8

methyl ...:

methylene blue: 3,9-bisdimethylaminophenazothionium chloride trihydrate, C16H18N3SCl.3H2O, a thiazine dye and redox indicator.

microcosmic salt: an acid sodium ammonium phosphate, NaNH4HPO4.4H2O, found in blood and natural waters.

milk: mineral "milks" or magmas are aqueous suspensions

Millon's base: (HOHg)2NH2OH, formed from a solution of mercuric oxide in ammonium chloride; named for A. N. E. Millon.

mineral alkali, common: hydrated sodium carbonate (fossil alkali, marine alkali, soda)

mineral dye: an inorganic pigment. Examples include mineral ...

minim: See apothecary measures.

minium: red lead oxide, Pb3O4 [Lavoisier, Priestley] (red lead [Priestley], Paris red). Minium once referred to cinnabar (mercuric sulfide, HgS) as well, but now is used only for its cheif adulterant, red lead oxide.

Mohr salt: ferrous ammonium sulfate, (NH4)2Fe(SO4)2.6H2O, named for Karl Friedrich Mohr.

molecule: does not necessarily correspond to the modern conception of two or more atoms chemically bound together. Avogadro, for example, meant something like "ultimate particle of a substance"; his elementary molecule corresponds to a modern atom and his composite molecule to a modern molecule. (See atom.)

Monsel salt: an iron sub-sulfate, Fe4(SO4)5O.

Monthier blue: a blue pigment, FeNH4[Fe(CN)6].

Moon (Luna): In astrological and alchemical thought, the seven heavenly bodies known to the ancients were associated with seven metals also known in antiquity. The moon was associated with silver (argentum). See lapis lunaris, lunar caustic.

mosaic gold: a tin(IV) sulfide, SnS2 pigment.

muriate: chloride; see muriatic acid. [Avogadro, Gay-Lussac, Thenard, T. Thomson]

muriatic acid: hydrochloric acid, HCl (acidum salis, marine acid, spirit of salt); muriatic gas is gaseous HCl. [Black, Gay-Lussac, Prout, Scheele, Thenard, et al.]

mustard gas: a di(chloroethyl)sulfide, (ClCH2CH2)2S, used as a chemical weapon in World War I

naphthalene yellow: a dinitro 1-naphthol, C10H5(NO2)2OH.

Naples yellow: lead antimoniate, Pb3(SbO4)2, used as a yellow pigment.

natrium: Latin for sodium, hence the symbol Na.

neutral red: dimethyldiaminotoluphenazine hydrochloride, also known as toluylene red; an acid-base indicator that changes from blue to magenta as the pH is raised through 7.5 and then to orange-yellow as pH is raised through 8.

nile blue: C20H19ON3, an aniline dye and acid-base indicator that changes from yellow through blue to magenta as the pH is raised

niton: the element radon, Rn, or one of its isotopes, 222Rn (half life = 3.8 d). See emanation and table of isotopes.

nitre or niter: potassium nitrate, KNO3 (saltpeter). Black gunpowder was made from nitre, charcoal, and sulfur. [Cavendish, Mayow, Priestley, Rayleigh, Watt, et al.].

nitric acid: formerly referred to nitrogen dioxide, NO2 [Avogadro, Dalton, Gay-Lussac, Lavoisier et al.] or nitrogen pentoxide, N2O5 [Prout]

nitrous acid: formerly referred to nitric acid, HNO3 (aqua fortis, spirit of nitre) [Lavoisier], or nitrous acid, HNO2, or a mixture of these acids; or one or more of the nitrogen oxides N2O3, NO2, N2O4, N2O5 [Avogadro, Dalton].

nitrous gas: specifically nitric oxide, NO (nitrous air) [Avogadro, Dalton, Gay-Lussac, T. Thomson, et al.]; or a mixture of nitrogen oxides such as that produced by the action of nitric acid on a metal in the presence of air

Nordhausen acid (also oleum): fuming sulphuric acid, i.e. a solution of sulfur trioxide, SO3, in concentrated (about 98%) sulfuric acid.

ocher or ochre: Ochers are inorganic pigments, mostly oxide minerals. Unmodified, ocher usually refers to an iron oxide. Specific ochers include: {Hackh}

oil of ...: Click here for structures. olefiant gas: ethene, C2H4 [Dalton, Prout, Thenard, T. Thomson, et al.]. See Dutch oil.

oleum: Latin for oil. Also, fuming sulfuric acid (Nordhausen acid)

once: Unit of mass in late 18th-century France; see livre. [Lavoisier]

orpiment: arsenic(III) sulfide, As2S3 (yellow arsenic, King's yellow). Red orpiment is arsenic(II) sulfide, As2S2, also known as realgar or red arsenic.

oxymuriatic acid (also oxygenated muriatic acid): chlorine, Cl2 (dephlogisticated marine acid); named on the belief that it was a compound of oxygen and HCl (muriatic acid). [Avogadro, Berzelius, Davy, Thenard]

Paris ...

patent yellow: lead oxychloride, PbO.PbCl2.

pearl ash: impure calcined potassium carbonate, K2CO3

Péligot's salt: potassium chlorochromate, KCrO3Cl, named for Eugène Péligot.

Perkin's mauve or violet: see aniline purple

phenol red: phenolsulfonphthalein, C19H14O5S, an acid-base indicator that changes from yellow to red as the pH passes through 8

phlogiston: a hypothetical elastic fluid which was seen as a metalizing and combustible principle. Metals were seen as the result of combining calces with phlogiston; smelting expelled the phlogiston. In combustion, phlogiston leaves the combustible body to combine with air or saturate air. The theory of phlogiston is associated with Stahl. [Cavendish, Priestley, Scheele, Watt et al.]

phosphuretted hydrogen: phosphine, PH3 [Dalton]

pied: Unit of length in late 18th-century France: 1 pied (Paris foot) = 12 pouces; 1 pouce (Paris inch) = 12 lignes. In modern units, the pied is equivalent to 0.325 meters or about 1.07 feet in the "English" system still commonly used in the United States. [Lavoisier]

pinte: volume unit in late 18th-century France, equal to 2.01508 English pints, 58.145 cubic inches, or 0.953 liters. [Lavoisier]

Plimmer's salt: sodium antimony tartrate, Na(SbO)C4H4O6.

plumbago: a lead ore, including lead oxide (litharge) or lead sulfide (galena); or graphite (black lead). [Lavoisier, Priestley, Thenard]

Plessy's green: chromium(III) phosphate, CrPO4, a green pigment; also Arnaudon's green.

plumbum: Latin for lead, hence the symbol Pb

pompholix: crude zinc oxide, ZnO (flowers of zinc). [Lavoisier]

potash: crude or purified potassium carbonate, K2CO3 (vegetable alkali, pearl ash) or crude sodium carbonate leached from the ashes of plant material; or potassium hydroxide, KOH (lye), or even potassium oxide, K2O. [Dalton, Rayleigh, T. Thomson et al.]

pouce: Unit of length in late 18th-century France; see pied.


Prussian blue: complex salts used in inks and dyes resulting from the oxidation of the white precipitate of a solution of iron(II) sulfate, FeSO4, and potassium ferrocyanide, K4Fe(CN)6.

prussiate: a cyanide, CN-, ferricyanide, Fe(CN)63-, or ferrocyanide, Fe(CN)64-.

prussic acid: hydrocyanic acid, HCN [Berthollet, Gay-Lussac, Prout]

pyrite or pyrites: originally any "fire-stone" from which sparks could be struck; eventually an iron sulfide or iron-copper sulfide. [T. Thomson]

pyroligneous acid: distillate from wood, containing acetic acid, methanol, and acetone

quicksilver: liquid mercury metal. [Boyle, Cavendish, Priestley, Torricelli]

racemic acid: an optically inactive form of tartaric acid consisting of equal quantities of optical isomers. Racemic originally referred to the origin of the acid (grapes), but now (in chemistry) refers to an optically inactive mixture of optically active isomers. [Pasteur]

radio- See table.

radium ... See table. Rankine scale: absolute temperature scale (i.e., one in which absolute zero is assigned the value zero) named after the 19th-century Scottish engineer William Rankine and denoted by °R. One Rankine degree is the same size as a Fahrenheit degree, so absolute zero (-460°F) is 0°R, the normal freezing point of water (32°F) is 492°R and the normal boiling point (212°F) is 672°R. (See Celsius scale, Fahrenheit scale, Kelvin scale.)

realgar: a native red or orange arsenic(II) sulfide, As2S2 (red orpiment, red arsenic, ruby arsenic, ruby sulfur)

Réaumur scale: temperature scale devised in 1731 by R. A. F. Réaumur and denoted by °R. The normal freezing point of water is 0°R and the normal boiling point of water is 80°R. (See Celsius scale, Fahrenheit scale, Kelvin scale.) [Lavoisier]

regulus: A metal was formerly called the regulus of the ore from which it was reduced [Scheele]; "regulus" (without further specification) meant regulus of antimony (i.e., antimony in modern nomenclature). [Lavoisier]

Reinecke's ...

retort: a container with a long tubular neck used by chemists and alchemists for distillation and the like. [Black, Cavendish, Lavoisier, Scheele]

reverberatory furnace: a furnace constructed so that a sample placed within it is heated from above as well as from the fire beneath it. For example, the furnace may have a top which reflects heat on the sample from the fire below it. [Black, Lavoisier]

rochelle salt: potassium sodium tartrate, KNaC4H4O6.4H2O, named for the French seaport La Rochelle, where the compound was prepared; also known as Seignette's salt, after the apothecary who first prepared it.

Röntgen rays: X-rays, named after their discoverer, Wilhelm Röntgen.

ruby: Ruby itself is a red corundum, Al2O3

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