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RES
R
RADICAL VINEGAR. See AcetousAcid.
RAGG. See Basalt.
REALGAR. See Arsenic, Sulphuret of.REALGAR, Native. See Arsenic, ores of.RECEIVER, or RECIPIENT. \ ...
RECIPIENT, Italian. / Articies
of chemical apparatus, for an account of whichfee the Appendix ,
RECTIFICATION.
This term implies the repetition of the pro-ceffes of diftiilation or Sublimation, generallywith a lefs degree of heat than at Sirft, in orderthereby to purify the fubftances which arethe fubjefls of them from all foreign matterswith which they may be mixed. Thus alcoholis rectified by rediltilling it at a gentle heat, bywhich it is feparated from the water and otherimpurities contained in common diftiliedfpirits.
RED CHALK or REDDLE. See Iron ,ores of, p. 587.
RED LEAD or MINIUM. See Lead ,oxyds of.
RED SCHORL. See Titanium, ores of.
REDUCTION.
Is the decompofition of a metallic oxyd fo asto leave the metal in a State of greater or lefspurity, and exhibiting the loftre which is foeminently charaCteriltic of metallic bodies.Reduction is for the mod part effected bycharcoal and a high temperature, either with orwithout the affiftance of fluxes For the vari-ous modes of reduction in aCtual pra£lice, feethe articles of the different metals.
REFINING Gold and ‘.ilver.
For a particular account of the method ofpurifying thefe metals, fee the articles Assay,Gold and Silver .
A fubftance that is either incapable, or evenvery difficult of fufion, is faid to be refrafitory,fuch are quartz, pure clay, platina, &c.
REFRIGERATORY.
An article of chemical apparatus, for a de-scription of which fee the Appendix .
KEGULUS. Konig. Germ.
The term in its moil extenfive fenfe means ametal hi the proper metallic ftate. Although avery convenient word, it is not much in life atpreient, being profcribed by the chemical neolo-gilts. By the old chemifts it was chiefly ufeclas a dift'mCtive appellation in thofe cafes where
a metal and one of its ores happened to becalled by the fame name. Thus the grey ful-phuret of antimony, was known by the nameantimony, long before it was fufpeoted to con-tain a peculiar metal, hence when this difco-very took place, the metal was called Regulusof antimony , to diftinguifh it from the ore fromwhich it was procured. F'or a Similar reafonthe metals arfenic and cobalt were called Reguliof arfenic and cobalt.
RESIN. Harze. Germ.
This term is given to a very important clafsof vegetable fubftances of which there is agreat variety of Species, differing from eachother in confluence, colour, fmell, and in Somedegree in chemical composition.
The origin of all the reflns is the fame, thatis, they exiude Spontaneously, or are extractedby incilions made in the bark of the refmoustrees, and moll of them gradually harden byexpofure to air. A further portion of the famerefin may alfo be always extradited artificiallyfrom the tree that yields it, by chemical me-thods. Refin is alfo very generally met within certain parts of vegetables, though its quan-tity is fo Small, or its combination with otherconftituent parts is fo Strong as not to appearin its proper form till extracted by chemicalanalyfis. Thus the bark of the cinchona con-tains no inconfiderable quantity of refin thoughnone appears to the eye on mere infpeClion,or (probably) could be extracted by incifionthrough the living tree.
The chemical properties which are ufuallyunderltood to characterize a refill, are the fol-lowing: it is firft Softened and then melted byheat, and when kindled it burns readily witha Strong and generally fragrant fmell, withcopious flame and fmoke, and leaves Scarcelyany reiidue behind. It is infolubie in waterand molt watery liquids, and is not eaf/\> aCtedon by acids or alkalies, except they are concen-trated, and the aCtion aflilted by heat or longdigeition. But it readily and totally diflblvesin alcohol, forming a clear, but coloured, Solu-tion from which by far the greater part of therefin is precipitated in a pulveru e.u form unal-tered, by the addition of water, which immedi-ately renders the Solution op .!•:■■ and turbid. Itis alfo Soluble in Sulphuric tber, and in thefixed and volatile oils, particularly the latter.
But though all refins agree in the qualities of