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.

    32/748 (page 28)
    the equations as follows : V/ = VX(l +0.00366 (t' — t)) X §7, where (r/ — t) is a VH plus quantity, and V/ = H 00366 (t' — t))' where the reduction is from a higher to a lower temperature. These formulas may be used for corrections for both tempera- ture and pressure at the same time. Example.—A given volume of air at 740 mm. and 150 C. measured 452 c.c. ; what will it measure at 760 mm. and o° C. ? Substituting, we have : V' = 452 X 740 = 4I72CC 760 X (1 +(0.00366X15)) '' ' ' Standard Temperature and Pressure.—Variations of tem- perature and pressure produce such important variations in volume that it is frequently necessary, when comparing observations, to reduce them to some standard temperature and pressure. The standard temperature used by most scientific men is o° C. But 6o° F., corresponding to 15.50 C., being about the ordinary temperature of the air, is sometimes found to be more convenient, and is frequently used. By standard conditions of temperature and pressure are usually meant, o° C. and 760 mm. pressure. Constitution of Gases.—Law of Avogadro or Ampere.— This law states that equal volumes of all bodies in the state of gas, and at the same temperature and pressure, contain the same number of molecules. As a necessary deduction from the law it follows: (1) That all gaseous molecules occupy the same space. (2) That the weights of equal volumes of any two gases are to each other as the weights of their molecules; or, in other words, the specific gravities of any two gases must be to each other as the weights of their molecules. This law is of vast importance to the chemist, and is considered the basis of most of the modern notions of chemistry. Although it would be out of place here to enter into such a discussion, this law is capable of mathemati- cal proof, starting with the assumption that masses are composed of molecules in a state of motion. Size and Weight of Molecules.—That molecules actually exist, and that they are in constant motion in straight lines within the gas, there seems to be at present little room for doubt. Various recent experiments, drawn from many sources, have given us proofs of these facts. Starting from certain well-established facts, physicists have been able to calculate the absolute number of molecules in a given space, their absolute weight, size, velocity, and the spaces between two neigh- boring molecules. What was at first a mere hypothesis is fast be- coming a demonstrated fact. According to these calculations, a cubic centimeter of air contains twenty-one tril-