MENSTRUUM

, Solvent, or Dissolvent, any fluid that will dissolve hard bodies, or separate their parts. Sir Isaac Newton accounts for the action of Menstruums from the acids with which they are impregnated; the particles of acids being endued with a strong attractive force, in which their activity consists, and by virtue of which they dissolve bodies. By this attraction they gather together about the particles of bodies, whether metallic, stony, or the like, and adhere very closely to them, so as scarce to be separated from them by distillation, or sublimation. Thus strongly attracting, and gathering together on all sides, they raise, disjoin, and shake asunder the particles of bodies, i. e. they dissolve them; and by the attractive power with which they rush against the particles of the bodies, they move the fluid, and so excite heat, shaking some of the particles to that degree, as to convert them into air, and so generating bubbles.

Dr. Keill has given the theory or foundation of the action of Menstruums, in several propositions. See Attraction. From those propositions are perceived the reasons of the different effects of different Menstruums; why some bodies, as metals, dissolve in a saline Menstruum; others again, as resins, in a sulphureous one; &c<*> particularly why silver dissolves in aqua fortis, and gold only in aqua regis; all the varieties of which are accountable for, from the different degrees of cohesion, or attraction in the parts of the body to be dissolved, the different diameters and figures of its pores, the different degrees of attraction in the Menstruum, and the different diameters and sigures of its parts.