Seft. 8.

as yet we are not fully acquaintedwith the Proportion there is betwixtthe Pores and Coheûon of Gold andSilver, nor with the Proportion ofthe attractive Forces of the Metals,and the . Menflruums, which is ne-ceifary to make this Solution : Tho'perhaps» whenExperiments are more

Of Extraction.

-9

accurately made, and eximin'd byMechanical Principles, we may nolonger remain in Ignorance aboutthem. At preiènt, it is enough forour purpofe, if from Numbers andCalculations we can point out theway, which leads to a Solution ofthis Phenomenon.

SECT. VIII.Of Extraclion.

Extraction, taken in its largeftSenie, ilgnifies any Solutionmade by Menflruums, unlefs therebe allow'd, as perhaps very wellmay, this difference betwixt them,That in Solution the Menflruumsablbrb the whole Subftance of theBody ; but in this, they only carryoft" certain Particles of it : And inthis Senfe Camphire is diflolv'd inSpirit of Wine. But Jalap is moreproperly laid to be extraèted ; forthe Re/in only is diflolv'd in theMenftruum, the other Particles be-ing left almoft untouch'd. But the'Extraction now to be treated of, isfuch an InfpifTation, or tkickningofsi Solution, as when a certain Quan-tity of the Mtnflruum is drawn off,the remaining Mixture is redue'd tothe Confiftence of Honey. Thusafter the Tincture from Saffron hasbeen plentifully drawn with Spiritef Wine, afterward« the Spirit isdrawn away by Diftiilation, to halfthe Quantity, and then the Remain-der is placed upon Sand, in an openVeiTel, to the end that the remainingMoifture may evaporate as far as ne-ceflary. By this Contrivance, theParticles of the Saffron are fo broken,and divided by the Spirit, that theyvery eafily mix with it, and producea fumciently liquid Tincture ; but

there being fcarce any Spirit left af-ter Diftiilation, the remaining Mat-ter muft necefianly thicken ; andwhen it is put into an open Veilèl,and the more fubtle Parts are dilîi-pated by the Force of the Fire, itwill be redue'd into a much thickerConfidence than it was before,whichis then call'd an Extract. The iaineProcefs is ufed in making the Ex-traéis of Gentian ¡Liquorice, Extr. E#-flachii, and the Aloeph angin Pill ;where the Spirit fs drawn a-way by Diftiilation ,' and willferve tlie fame Purpoiès over a-gain. Sometimes the |uices of Ve-getables run of themielves into Ex-tracts. Extraction, as perform'd af-ter this manner, does not requireany long Difcourfe to explain ; lincewhatever has. been iaid of Digefti-on, may very well be apply'd toit.

Extracts are chiefly made fromVegetables , and require differentMenflruums, according ro the diffe-rent Nature of the Plants ; as may b¿obferv'd, efpecially in Extracts fromGums : for iuch of thefe as ire Muci-laginous, as GumArabic. Tragacanth,&c. are not eafily diflolv'd but in a-aueous Liquors; on the other hand,Kefinous Gums, as Galbanum, Scam-mony, &c. muft have high rectifiedSpirits