A college text-book of chemistry . the height of the col-umn of mercury or water in thetube. Thus, if the arrangement isas represented in Fig. 4, the heightof the mercury column above thelevel of the mercury in the troughbeing 100 millimetres, and the pres-sure of the atmosphere 760 milli-metres of mercury; then the gas inthe tube is plainly not under the fullatmospheric pressure, for the atmos-phere is supporting a column ofmercury 100 millimetres high, andthe pressure actually brought to bearon the gas corresponds to 760 — 100 = 660 mm. of that in this case the volume of gas
A college text-book of chemistry . the height of the col-umn of mercury or water in thetube. Thus, if the arrangement isas represented in Fig. 4, the heightof the mercury column above thelevel of the mercury in the troughbeing 100 millimetres, and the pres-sure of the atmosphere 760 milli-metres of mercury; then the gas inthe tube is plainly not under the fullatmospheric pressure, for the atmos-phere is supporting a column ofmercury 100 millimetres high, andthe pressure actually brought to bearon the gas corresponds to 760 — 100 = 660 mm. of that in this case the volume of gas actually measured is75 cc. Call this V. What would be the actual volume V underthe standard 760 mm. ? We have seen that VP = VPNow, in this case P= 760, V - 75, and P - 660. Therefore-, 760F=75 x 660, or 7= *6Q = In all cases it is necessary to make a correction similar to thisin dealing with the volumes of gases. The correction for tem-perature and that for pressure may be made in one operation,the formula being _ VP V =. Fie. 4. 760(273 + *) or 7= 760(1 + ) in which V= the volume of the gas at 0° and 760 mm. pressure ;V = the observed volume; t = the observed temperature;P = the pressure under which the gas is measured. Some of 46 COLLEGE CHEMISTRY. B the most important ideas that have been introduced into chem-istry with a view to explaining the regularities observed in thequantities of substances which act uponone another chemically have their originin observations on the conduct of is therefore of the highest importancethat the student should familiarize himselfwith the meaning of the expression, thevolume of a gas under standard condi-tions. The presence of water-vapor in agas also influences its volume, increasing itby the same amount as it would be in-creased if the pressure were diminished bya quantity equal to the pressure of thewater-vapor for the given formula for making all the correc-tions required in determining the volu
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