. Chemistry: general, medical, and pharmaceutical, including the chemistry of the U. S. Pharmacopia. A manual on the general principles of the science, and their applications in medicine and pharmacy. fourthits bulk—in short, to such an extent that in many cases the mole-cules sufficiently approximate to form a liquid. In a liquid themolecules are still free to glide about with, ease amongst each other;and though in solids they exhibit less mobility, still even solids maybe compressed by powerful pressure, so that probably in no instanceare molecules in absolute contact. (Moreover, from the re
. Chemistry: general, medical, and pharmaceutical, including the chemistry of the U. S. Pharmacopia. A manual on the general principles of the science, and their applications in medicine and pharmacy. fourthits bulk—in short, to such an extent that in many cases the mole-cules sufficiently approximate to form a liquid. In a liquid themolecules are still free to glide about with, ease amongst each other;and though in solids they exhibit less mobility, still even solids maybe compressed by powerful pressure, so that probably in no instanceare molecules in absolute contact. (Moreover, from the researchesof Caignard de la Tour and of Andrews there would seem to be nosharp lines of demarcation between the gaseous, liquid, and solidconditions of substances.) Ones mental picture of the relativeposition of the molecules of gaseous, vaporous, liquid, or solidmatter must be such a picture as that of the moving particles ofdust in the air of a room, or such a relation to each other as that ofthe planets and stars suspended in space. There is abundant experi-mental evidence to warrant such a conception. A clear, transparentfluid appears perfectly homogeneous, but is not so. Its particles are. CHEMICAL PHILOSOPHY. 43 not in contact. Every person who has mixed 5 pints of rectifiedspirit with 3 pints of water knows that the 100 fluidounces of spiritand 60 fluidounces of water do not when mixed give 160 ounces ofproof spirit, but only 156 ounces ; the molecules of the liquidshave gone closer together, having probably a little attraction for eachother. Having gone closer together, they were not previously soclose together, the necessary conclusion being that even liquids areporous. Why a gas under pressure should immediately return toits original bulk when the pressure is removed, while a liquefied orsolidified gas only slowly resumes the gaseous or vaporous state, is aquestion which requires for discussion a knowledge of the nature offorces other than the chemical. For it must be
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