Edward G. Janzen'
An Automatic Leveling Bulb Apparatus
Iowa State University Ames
In studies of the rate of reaction of oxygen with carbanionsl. we have used a gas buret with an automatic mercury-bulb leveling apparatus which maintains a constant oxygen pressure mithiii the system (Fig. 1). The mercurv bulb is raised bv means of a t,hreaded rod which Dasses through a threaded sleeve in the bulh support. A 3/8-in. brass rod was used with approximately 16 threads to the inch. A Fisher leveling bulh ~~
~
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21 RPM WONEYWELL TOGGLE s
W
I
T
C
H
-
BOLT W I T H WING N U T FOR EASY REMOV4L
E
S
,
MOTOR ~
T O RELAY
MICRO SWITCH MERCURY BULB SUPPORT THREADED S L E E V E
IDE WHEEL
2 7 &IN.
completely and turning it top to bottom. With a reversing motor, the hulb support can be lowered without removal of the rod hut this method is time consuming. A microswitch near the top, when activated by the bulb support, breaks the motor circuit and prevents the bulb from rising too high on the rod. The ends of the rod are hollowed to fit over a ball-bearing seated on the base. The base is built from a ring of 3 1/2-iu.diameter covered with '/4-in. aluminum. The motor support was made from '/,,in. aluminum bent upward to provide for a switchboard. The threaded rod is turned by a slow-speed motor activated by a Niagara Electron Laboratories "Thermocap" relay (Fig. 2). The activation is based on a conductivity principle. A small clip placed around the manometer glass tube on the mercury miniscus is sensitive to the drop in the mercury level of the manometer as the pressure decreases. A sensitivity range of + 1mm at atmospheric pressure can readily be attained if a second grounded clip is used near the clip connected to the relay,
B R l S S ROD W I T H G U I D E GROOVE TOGGLE
WITH HOLLOWED ENDS TO F I T OVER
MICRO SWITCH
RELAY
I GROUND
Figure 1.
support was adapted for the apparatus by fittiug a threaded sleeve into the hole for the rod. A guidewheel of l/s-in. brass and approximately 8/1-in. diameter was mounted on the back of the hulb support to fit into a guidegroove of a S/s-in.brass rod mounted parallel to and behind the threaded rod. The groove is approximately in. wide by in. deep which allows the guidewheel to turn freely as the bulb moves u p ward. When the bulb has risen to the top and it is necessary to refill the gas buret, the bulb support can be returned to a lower position by removing the rod
' Present address: University of Georgia, Athens. G. A,. JANZEN. E. G.. BECKER. H.-D..' AND SMENRUSSELL. F. J:, J . AA. Chem. ~ o e . ,84,2652 (1962). TOWSK~, a
RUSSELL, G. A,, AND JANZEN, E. G , J . Am. Chem. Soe., 84,
4153 (1962).
TOGGLE SWITCH
TO SYSTEM-
3
Figure 2.
The top of the apparatus was clamped to a rigid stand by means of two short L/2-ii~. rods fastened to the aluminum motor support. The base was secured by clamping the ring to the same stand. Acknowledgment is made to the Petroleum Research Fund, administered by the ACS, for support of this research. The author wishes to express his gratitude to Harvey Meyer who built the apparatus.
Volume 41, Number 5, May 1964
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281
