=MET'ALS.= _Syn._ METALLA, L. Metals are elementary bodies, which are generally distinguished by their lustre and power of conducting heat and electricity. When their solutions are electrolysed, the metals always appear at the electro-negative surface, and are hence termed electro-positive elements.
Formerly, when science was much less advanced than at present, the metals constituted a well-defined class. The properties which were regarded as specially characteristic were physical, and were not founded on chemical relations; thus, lustre and high specific gravity were considered to be essential characters of all metals. But we are now acquainted with metals which have a lower specific gravity than water (lithium, sodium, &c.), and with so-called non-metallic elements which present a strong metallic lustre (carbon in the state of graphite, crystallised silicon). It will therefore be seen that the term 'metal' is rather conventional than strictly scientific. By far the greater number of elementary bodies at present known are metals. Their physical characters and leading chemical properties are noticed under each of them in its alphabetical place. The following table exhibits some useful particulars:--
TABLE _of some of the properties of some of the metals._
Names arranged in the order of their /-----------------------/---------------------- Ductility. Malleability.
Gold. Gold.
Silver. Silver.
Platinum. Copper.
Iron. Tin.
Nickel. Platinum.
Copper. Lead.
Zinc. Zinc.
Tin. Iron.
Lead. Nickel.
Names arranged in the order of their /-----------------------/---------------------- Power of conducting Power of conducting Heat. Electricity.
Silver. Silver.
Copper. Copper.
Gold. Gold.
Tin. Zinc.
Iron. Iron.
Lead. Tin.
Bismuth. Lead.
Antimony.
Bismuth.
=METANTIMON'IC ACID.= H_{4}Sb_{2}O_{7}. The name given by M. Fremy to that variety of antimonic acid obtained by decomposing pentachloride of antimony with excess of water. It differs from common antimonic acid in being tetra, and forming two different classes of salts with the acids.
The acid metantimoniate of potassium is the only reagent which yields a precipitate with the sodium salts, and is therefore of great value in chemical analysis. It is prepared by fusing antimonic acid with excess of potassa, in a silver crucible, dissolving the fused mass in a little cold water, and allowing it to crystallise in vacuo. The resulting crystals (metantimoniate of potassa), by solution in pure water, are resolved into free potassa and the acid salt. See ANTIMONY.
=METAPEC'TIC ACID.= See PECTIN.
=METAPEC'TIN.= See PECTIN.
=METAPHOSPHOR'IC ACID.= See PHOSPHORIC ACID.
=METHEG'LIN.= _Syn._ HYDROMELI, H. VINOSUM, MELLIS VINUM, L. _Prep._ From honey, 1 cwt.; warm water, 24 galls.; stir well until dissolved; the next day add of yeast, 1 pint, and hops, 1 lb., previously boiled in water, 1 gall.; along with water q. s. to make the whole measure 1 barrel; mix well, and ferment the whole with the usual precautions adopted for other liquors. It contains on the average from 7% to 8% of alcohol. See MEAD.
=ME'THYL.= CH_{3}. The hypothetical radical of PYROXYLIC SPIRIT (WOOD-SPIRIT, METHYLIC ALCOHOL) and the methyl series. It forms a number of compounds analogous to those of ethyl.
=METHYLAMINE.= _Syn._ METHYLIA. CH_{3}H_{2}N. A colourless gas possessing a very powerful odour of ammonia, and a strongly alkaline reaction. It differs from ammonia, however, in being non-inflammable. In other respects it bears a considerable resemblance to it. Water at 55 Fahr. dissolves more than eleven hundred times its bulk of methylamine. It may be easily condensed to a liquid by means of a freezing mixture.
To obtain it nascent hydrogen is made to react on prussic or formic acid.
Methylia exists in herring brine, and is a frequent product of the destructive distillation of substances containing nitrogen. Most of its salts are very soluble in water.
=METHYLATED SPIRIT.= A mixture of 1 part of methylic alcohol (wood spirit) and 9 parts of ethylic alcohol (spirit of wine). See SPIRIT.
=METHYLENE CHLORIDE.= CH_{2}Cl_{2}. _Syn._ METHYLENE BICHLORIDE. There are various methods of obtaining this compound:--1. By heating chloroform with zinc filings and dilute sulphuric acid. 2. By acting on methylene iodide with chlorine. In this process prolonged treatment with chlorine, at ordinary temperatures, is required to remove the last traces of iodine.
(Buttlerow.) Chloride of methylene is a colourless mobile fluid, having a smell like chloroform, and a burning taste. It is used as an anaesthetic in place of chloroform. According to Dr Armstrong, the substance known as METHYLENE ETHER is a mechanical mixture of bichloride of methylene and ethylic ether. Dr Richardson says of this latter it is not so quick in its action as the methylene chloride, but that it is safer. See ANaeSTHETICS.
=METHYLIC ALCOHOL.= See WOOD SPIRIT.
=MEZE'REON.= _Syn._ GAROU; MEZEREON BARK, MEZEREI CORTEX (B. P.); MEZEREON--Ph. L., E., & D. The dried bark of the _Daphne Mezereum_, mezereon; or _Daphne Laureola_, spurge, or wood-laurel. The "bark of the root of _Daphne Mezereum_," or spurge olive. (Ph. L.) A stimulant and diuretic. It is employed as a sudorific and alterative, in syphilis, rheumatism, scrofula, and chronic cutaneous diseases, usually in conjunction with sarsaparilla. It has also been used as a masticatory in toothache, paralysis of the tongue, &c. On the Continent it is used as a vesicant. For this purpose it is softened by soaking it in hot vinegar, and is then bound on the part, and renewed after intervals of some hours, until vesication is produced.
=MICE.= See RATS.
=MI'CROSMIC SALT.= NaNH_{4}HPO_{4}, _Syn._ TRIBASIC PHOSPHATE OF SODIUM AND AMMONIUM. _Prep._ 1. Phosphates of soda and ammonia, equal parts; water, q. s.; dissolve separately, mix the solutions, evaporate, and crystallise. A slight excess of phosphate of ammonia aids the crystallisation.
2. (Fownes.) Phosphate of sodium, 6 parts; water, 2 parts; liquefy by heat, and add of sal ammoniac (in powder), 1 part; common salt separates, and after its removal the liquid is concentrated so that crystals may form. Used as a flux in blowpipe assays.
=MI'CROSCOPE.= The value of the microscope in chemistry and the collateral sciences is now so generally acknowledged that it would be folly to do more than merely allude to the subject here.
In the COMPOUND MICROSCOPE, which has quite superseded the 'simple microscope' as an instrument of research, the object is magnified in the first instance by the object-glass, and then remagnified by the eye-piece.
It follows, therefore, that the magnifying power of the instrument may be increased either by increasing the power of the object-glass or that of the eye-piece. It must be borne in mind, however, that in increasing the power of the eye-piece we do not magnify the object itself in a greater degree, but simply increase the image of the object formed by the object-glass. Any imperfections which may exist in the latter are thus greatly increased. At first the great drawback to the use of the compound microscope was its deficiency in achromatism; but the researches of Mr Lester and Dr Goring led to the achromatising of the object-glass, which was the first of the rapid strides towards perfection made by this instrument during the last twenty years. The two most useful object-glasses are the 'quarter-inch,' which should magnify from 200 to 220 diameters, and the 'inch,' which should magnify from 30 to 40 diameters. The definition of these glasses should be good, and they should transmit plenty of light. Any lines in a structure examined by them should appear sharp and distinct, and there should be no coloured fringes around the object. It is of great importance that the object-glasses are kept perfectly free from dust. A few shreds of wash-leather of the finest quality should be kept in a pill-box for cleaning them. Before rubbing them with the leather they may be breathed upon, but no whiting or liquid of any kind should be used, as each object-glass, being achromatic, is a very delicate piece of workmanship, consisting of two lenses of flint and crown-glass cemented together by Canada balsam. Compound microscopes are now sold by the best London makers at very low prices. A really good instrument, adapted to most of the wants of the chemical, pharmaceutical, or medical student, may be obtained for five guineas.
The following formulae for the preparation of the chief substances, together with the principal reagents required in the working of the microscope, are from Dr Lionel Beale's valuable book, 'How to Work with the Microscope,'[36]
[Footnote 36: Harrison, 59, Pall Mall.]
_Reagents_--
1. Alcohol, of various strengths.
2. Ether, to dissolve oil globules.
3. Nitric acid (1 part of strong acid to 5 of water)
4. Sulphuric acid (1 to 5).
5. Hydrochloric acid.
6. Acetic acid, glacial and dilute (1 to 5).
7. Chromic acid, very dilute, to harden tissues.
8. Solution of potash, saturated and dilute (1 to 10).
9. Solution of soda (25 gr. of fused soda to 1 oz.).
10. Ammonia (1 part of the strongest solution to 3 of water).
11. Nitrate of baryta, a cold saturated solution of.
12. Nitrate of silver (120 gr. to 2 oz.). These two are for the mineral acids.
13. Oxalate of ammonia in solution. Test for lime.
14. Solution of iodine saturated, _i.e._ 1 to 7000 parts of water. Another solution is--1 gr. of iodine and 3 of iodide of potassium in 1 oz. of distilled water.