The Flow Of Gases In Furnaces

APPLICATION OF THE LAWS OF HYDROSTATICS

25

or 13 mm 45 of water. This pressure of 13 mm 45 is absolutely
necessary, as well as a slight additional pressure to overcome the
friction in the mains and impress upon the gas the necessary
velocity of flow. In the case of a blast furnace producing char-
coal iron, the pressure at the head of the furnace was 35 mm of
water, the gas mains being too small and poorly designed. This
bad construction of the gas mains could not be corrected without
a general reconstruction. The method of arriving at the resistance
caused by friction in the gas mains will be given later,

(c) Hydrostatic Pressure in Open-top Chambers Filled with a
Light Gas.—If an inverted test-tube is held vertically (Fig. 1.9)

O

T

H,2

T

FIG. 19.

FIG. 20.

and filled with hydrogen the pressure at the level 00 will be equal
to that of the atmosphere, and at the upper part there will be a
positive pressure + <5. This experiment may bo modified by using
a vessel filled with hydrogen (Fig. 20) which has a capillary
strangulation at the top surmounted by a thistle, and a U tube
at the bottom. The capillary tube is sealed with a drop of water,
permitting the hydrogen to escape, when its pressure exceeds
that of the atmosphere, without, at the same time, giving free
communication between the interior of the vessel and the air.
It necessarily follows that the pressure in the interior of the vessel
at the level 00 is equal to that of the atmosphere. What will
be the pressure indicated by the manometer U tube filled with
water at K connected with the lower part of the vessel? Upon