[Footnote 1: Read at the meeting of the Chemical Section of the
Franklin Institute held March 17, 1891.]
By H. PEMBERTON, Jr.
Chemists who do not happen to have in their laboratories oil or air
baths for heating closed tubes can make an air bath at short notice
from materials furnished by all dealers in steam fittings.
_Order_:
(1) One four-inch wrought iron pipe, eighteen inches out to out, with
usual thread on each end. At about nine inches from either end this
pipe is drilled and tapped for a one-inch nipple, in such a manner
that a pipe introduced would pass, not on a line with the radius, but
about half way between the axis of the four-inch pipe and its walls;
in other words, it would be on a line with a chord of the circle.
(2) One one-inch wrought iron nipple, two inches long, one-inch thread
on one end.
(3) Two four-inch malleable iron caps, drilled and tapped for a
one-inch pipe.
(4) One one-inch wrought iron pipe, twenty-four inches out to out,
with a three-inch straight thread on each end.
(5) Two one-inch iron caps. A hole, one-eighth of an inch in diameter,
is drilled in the end of one of these caps.
The above order can be given _literatim_, and will be understood by
the dealer, who will furnish, at a trifling cost, the materials, cut
and tapped as ordered.
Fig. 1 shows how the whole is put together. The numbers on the figure
correspond also to the numbers of the paragraphs of the order as given
above.
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
Fig. 2 is an end section. A cork is inserted in 2 and through it a
thermometer, the bulb of which is on a level with the interior pipe.
The whole is supported on a few bricks at either end, and is kept
steady and in place by a couple of weights or half bricks. It is
heated by one or two Bunsen burners, according to the temperature
desired.--_Jour. Fr. Institute_.
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