Another process, known as the Hildebrandt process, is coming into use in
this country. It is a later process and is used in Germany to a much
greater extent than the Linde process. The Superior Oxygen Co. has secured
the American rights and has established several plants.

_Oxygen Cylinders_.--Two sizes of cylinders are in use, one containing
100 cubic feet of gas when it is at atmospheric pressure and the other
containing 250 cubic feet under similar conditions. The cylinders are made
from one piece of steel and are without seams. These containers are tested
at double the pressure of the gas contained to insure safety while
handling.

One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and
therefore the cylinders will weigh practically nine pounds more when full
than after emptying, if of the 100 cubic feet size. The large cylinders
weigh about eighteen and one-quarter pounds more when full than when empty,
making approximately 212 pounds empty and 230 pounds full.

The following table gives the number of cubic feet of oxygen remaining in
the cylinders according to various gauge pressures from an initial pressure
of 1,800 pounds. The amounts given are not exactly correct as this would
necessitate lengthy calculations which would not make great enough
difference to affect the practical usefulness of the table:

Cylinder of 100 Cu. Ft. Capacity at 68 Fahr.

Gauge Volume Gauge Volume
Pressure Remaining Pressure Remaining