Smithsonian miscellaneous collections . \ \ \ \ \ \ & \ I \ 1\ \ \ \ \ \ \\ \| V \\ 1\ \ \ \ \\ 1I , ? 700-30° -20° -J0° 0° JO 20° 30°6° FIG. 3. GRAM-LINES OF SATURATION These saturation curves may also be transferred to another net-work of coordinates whose vertical axis, as before, shows the pres-sure while on the horizontal axis the number of grams is this case therefore p and x are the variable coordinates in theequation e - f (t) = xp622 -f- x constant, ADIABATIC CHANGES OF MOIST AIR NEUHOFF 475 which equation leads us to the construction of the isothermal curvesof saturation sho
Smithsonian miscellaneous collections . \ \ \ \ \ \ & \ I \ 1\ \ \ \ \ \ \\ \| V \\ 1\ \ \ \ \\ 1I , ? 700-30° -20° -J0° 0° JO 20° 30°6° FIG. 3. GRAM-LINES OF SATURATION These saturation curves may also be transferred to another net-work of coordinates whose vertical axis, as before, shows the pres-sure while on the horizontal axis the number of grams is this case therefore p and x are the variable coordinates in theequation e - f (t) = xp622 -f- x constant, ADIABATIC CHANGES OF MOIST AIR NEUHOFF 475 which equation leads us to the construction of the isothermal curvesof saturation shown in fig. 4. By using pressure and temperature as coordinates the adiabatsof the dry stage and of the condensation stage as well as the gram-lines may all be combined in one diagram, by the use of which itbecomes possible to determine all the adiabatic changes of moist airin successive series. Such a system of curves is shown in fig. 5. /O 15 300 m / a m ;f / / / / .* 1 / / / 4 — i 700 760 FIG. 4. ISOTHERMS OFSATURATION. -20° -/() (J° /O 20° M° FIG. 5. DIAGRAM OF ADIABATS Every point of the saturation curve that corresponds to a definitecondition p, t shows how many grams of aqueous vapor are con-tained in (1 + x) kilograms of saturated air. For instance, at 300temperature and 76omm pressure we have the gram line for 27grams. If this air is still in the dry stage and if the mixing ratiois 10 grams, then from the ratio 10 x 100 27 we obtain the relative humidity, 37 per cent. Conversely if for 200 and 76omm of pressure we have 20 per centas the relative humidity then, since the saturation curve at thispoint is 15 grams, we find the mixing ratio to be 15 X 20100 = 3 grams. The expansion continues along the adiabat of the dry stage untilthe point of saturation is reached, that is to say, until the adiabatof the dry stage intersects the gram line that corresponds to themixing ratio. 476 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 51 Thus for expansion from 300 and 76om
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