Chemistry : general, medical, and pharmaceutical including the chemistry of the British Pharmacopœia a manual on the general principles of the science, and their applications in medicine and pharmacy / by John Attfield.

  • Attfield, John, 1835-1911.
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Chemistry : general, medical, and pharmaceutical including the chemistry of the British Pharmacopœia a manual on the general principles of the science, and their applications in medicine and pharmacy / by John Attfield. Source: Wellcome Collection.

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    The percentage composition of a chemical substance liaving been determined by quantitative analysis, its formula is con- structed by the aid of the foregoing and other theoretical considerations. The correctness of such formula) can be verified by expert analysts, but must be taken for granted by learners. This subject will again be referred to in the latter part of this Manual. QUANTIVALENCE OF AtOMS. Turning from the weights of atoms, their value may now be considered, or their quantivalence. The chemical value of atoms in relation to each other may be compared to the ex- changeable value of coins. As compared with a penny, a groat is four-valued; as compared with hydrogen, carbon is quadrivalent. Here again hydrogen is conventionally adopted as the standard of comparison. An oxygen atom in its relations to an atom of hydrogen is bivalent (biv'-a- lent; of double worth, from his, twice, and valens, being worth) ; an atom of it will displace two atoms of hydrogen, or combine with the same number; nitrogen is usually trivalent (triv'-a-lent; from tres, three, and valens); and carbon quad-riv'-a-lent (from quatuw, four, or quater, four times, and valens). Chlorine, iodine, and bromine, as well as potassium, sodium, and silver among the metals, are, like hydrogen, univalent (u-niv'-a-lent; from iinus, one, and valens). Barium, strontium, calcium, magnesium, zinc, cad- mium, mercury, and copper, like oxygen, are bivalent. Phosphorus, arsenium, antimony, and bismuth, like nitrogen, usually exhibit trivalent properties; but the composition of certain compounds of these five elements shows that the several atoms are sometimes quinquivalent (quin-quiv'-a-lent; quinquies, five times, and valens). Gold and boron are triva- lent. Silicon (the characteristic element of flint and sand), tin, aluminium, platinum, and lead resemble carbon in being quadrivalent. Sulphur, chromium, manganese, iron, cobalt, and nickel are sexivalent (sex-iv'-a-lent; from sex, six, or seodes, six times, and valens), but frequently exert only biva- lent, trivalent, or quadrivalent activity. This qnaniivalencc (quant-iv'-a-lence ; from quantitas, quantity, and valens), also termed atomicity (maximum quantivalence), dynamicity, and equivalence of elements, may be ascertained at any time on referring to the Table of the Elements at the end of this