Text-book of medical and pharmaceutical chemistry / by Elias H. Bartley.

  • Bartley, Elias Hudson, 1849-1937.
Date:
[1899, ©1898]
Catalogue details

Licence: Public Domain Mark

Credit: Text-book of medical and pharmaceutical chemistry / by Elias H. Bartley. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    Chemism.—Atoms attract one another by a force called chemism or chemical affinity. Chemism holds atoms together to form molecules. It is to the molecule what cohesion is to the mass. Like cohesion, it only acts across inappreciable spaces. Inertia is that property of matter by virtue of which it has no power in itself to change its condition. This term is often incor- rectly limited to the tendency of a body when in motion to continue in motion, and when at rest to remain so. Chemical or physical changes never take place without the intervention of some external agency. Extension is that property of matter by virtue of which it occu- pies space. Its relative degree is obtained by means of weights and measures. The system of measures and weights in use in all scientific works is that known as the metric or decimal system. In most American and English medical books, though not in all, the English system is employed, while all nations of Continental Europe use the metric system; so that it is requisite that the student should be familiar with both. The unit of the metric system is the meter. The meter * is the length of a platinum bar de- posited in the public archives of France, and is 39.37 inches in length. The measure was obtained by taking tfotoo'o 0 Part °*~ tne quadrant of a meridian of the earth, or of the distance from the equator to the pole. The ratio of increase and decrease of the system is decimal, and consequently this system is sometimes known as the decimal system. The multiples of all the measures and weights are denoted by Greek numerals, used as prefixes, as will be seen by reference to the tables of weights and measures in the Appendix. Thus, in measures of length we have the meter, deka- meter, hectometer, and kilometer. The subdivisions are denoted by the Latin numerals, thus : meter, decimeter, centimeter, and millimeter. Gkeek. Latin. English. Deka. Decern. Ten. Ilekaton. Centum. One hundred. Chilios. Mille. One thousand. Murias. Ten thousand. The decimal subdivisions and multiples give a simplicity to the tables Avhich enables them to be easily learned and remembered, and brings into use in all calculations the easiest arithmetical processes. In square measure, measures of capacity, and measures of volume but * Also spelled metre.