365 OF ENGINEERING FORMULÆ.
Expansion' of Gases.
Boyle’s (Mariotte’s) Law.
“ The density of a gas is proportional to its pressure for tna
same temperature.” Saturated steam is not a perfect gas.
Perfect gases have as nearly as possible the same coem-
cient of expansion under all temperatures. .
p — Pressure at zero — 760 millimetres, or 29*92 niches
of mercury,
t = Temperature of gas.
a — Volume of gas at zero.
b — „ „ at any temperature t.
W = Weight „ at zero.
w — „ „ at any temperature t.
p = Pressure at any temperature i.
= Coefficient of expansion with each degree of tempera-
ture — -003665 Centigrade = "002036 Fahr.
p == P (1 + K t).
V — ____— . v = V (1 + K t).
1 + Kt w
W=w(l + Kt). w=sf^Kj-
Balloons.
W — Weight to be raised, including the weight of the
balloon itself.
A = Weight of a cubic foot of air.
G = „ .. the gas.
D = Diameter of the balloon.
/ 'V —
D — * -5236 (A - G)’
T„^o£tdy(with hydrogen gas, but varying with the
state of the a«here,^
The buoyancy of hydrogen is about 13-3 feet to a lb.
Formation of Balloon Segments. ,