360
16.
VACUUM TECHNIQUE
‘
area of 5.6
and large inthe lower pressure pump (diffusion —
area =
12.3 cm.2). - The boiler should have a large surface and
only a small quantity of oil is to be used, say 100 cc. of Apiezon oil
“” in the rst stage and an equal amount of ”B ” in the
second stage.
A central copper rod which rests on the oor of the
copper
boiler serves to support the umbrella (U) and to keep it
hot.
A glass heat insulator (1) is used around the outside of the
from va‘cuum
*
'
system
.
H
1‘
Pa
‘ —>
U
,
ÏÏ"-:.
| C2
P2
'_i:
.
+
;
| |
D
“
'.“- :.: ::.. .‘
.
C'
"
Ï'Ï
<—
forepump
|
.
ï‘
P,
Îï"
"
': :|
.
.°.
‘.
.
.
E
_
_
€
012345
E
Ï_î_:
_
CENTIMETERS
'
.
_
'A
_
B
'
' _
PIG. 16—7.
Diffusion pump using oil.
_
-
'
.
inner, copper tube to prevent volatilization of the oil after it has
_
,
COHd€HS€d‘ below. the jets. A copper bale plate at P also assists
_
in keeping the réturnirig oil in liquid form. The liquid oil returns
,
_
_
to the boiler thr0ugh ”several
pressed in the side of the
boiler wall. This feature is exaggerated in the drawing, at E.
_
Only a small
amount of cooling is needed in the thin
,
'
jacket (D). A cold bafe plate
essential to keep traces of “oil
_