Improved Stirrer and Bearing for Spinning Band Distillation Columns W. F. Pease, A. H. Gilbert, and Arno Cahn, Research & Development Division, Lever Brothers Co., Edgewater, N. J. of support for the loner portion L of the band is one cause of band “wobbling” sometimes encountered in ACK
the operation of spinning band distillation columns. Band wobble is undesirable not only because it indicates nonuniform rotation, but also because repeated flexing may ultimately lead to band rupture. T o avoid these difficulties, Murray positioned the band by means of several metal spider bearings placed a t intervals throughout the length of the column [Murray, K. E., J. Am. Oil Chemists’ SOC.28, 1 (1951)l. A single glass spider bearing at the lower end of the column has now been found effective in eliminating band wobble. Introduction of this bearing made it necessary to redesign the stirrer assembly. The new design possesses several desirable features. Figure 1 s h o w the bearing and the stirrer assembly in position at the lower end of a Nester Intermediate-Lab spinning band column (Nester and Faust, Wilinington, Del.). Figure 2 shows a top view of the bearing, which consists of a hole in the center of a glass spider 29/42 to sealed onto a standard T 24/40 reducing bushing adapter (fabricated by Ace Glass, Inc., Vineland, N, J.). The metal rod extension of the spinning band projects through the bearing approximately 3/8 inch and carries the stirrer assembly, which is shown as a top view in Figure 3. The assembly consists of a stainless steel cylinder and a loop of No. 18 gage Nichrome wire. Two stainless steel
1.
A
.
D = 0 0 6 2 inch
d
229/42 A d a p t e r reducing bushing t y p e Corning No 0025
Figure 2
t5mm
x D=O 0 4 2 i n c h
D=O 0 6 0 inch
LJ
D:lSmm
Figure I
e n l a r g e d view
Figure
3
Allen head screws, spaced 180” apart, hold the cylinder to the spinning band
in contrast to a single setscrew in the commercial stirrer. The .ivire loor,
ihe bearing is \yell wetted by (he refluxing liquid.
of appropriate size.
The stirrer assembly is superior to the commercial model in several respects. Symmetrical placement of the Allen head screws ensures good balance.
The authors are indebted to W. V. Dudley and Stanley Struniewski of the instrument shop for the fabrication of the stirrer assembly.
ACKNOWLEDGMENT
Solenoid-Operated Gas Sampler for Use in Gas Chromatography Richard C. Palmer, D. Keith Davis, and W. Van Willis, Engineering Experiment Station, Georgia Institute of Technology, Atlanta, Ga.
the radiation chemistry program of Itonsweep this laboratory an inert gas is used the radiation cell of the gas phase fragments which result from the radiation damage to a parent molecule. It is useful to sample the sn-eep gas periodically during an irradiation and to subject the sample to gas chromatographic analysis. The manually operated gas sample valves, which are commercially available have proved unsatisfactory for two reasons: These valves are subject to a leak rate which introduces extraneous results-eg., air peaks-and although the use of stopcock grease minimizes the leak, the grease also adsorbs the 894
ANALYTICAL CHEMISTRY
radiation products; and retention volumes vary from operator to operator, because of inherent differences in techniques. For these reasons an electrically operated sampler Kas devised for injecting gas samples into the chromatographic units. The electrically operated system is composed of two two-way and two threeway solenoid valves which are operated by a direct current power supply (direct current valves were chosen, as “chatter” is frequently encountered with alternating current valves). Figure 1 shows diagrams of the gas sampler in the nonenergized and in the energized states. When this system is in the
nonenergized state, valve I allows the carrier gas from the gas chromatographic unit to enter the separation columns directly; valves I11 and Is’ are closed to the carrier gas but allow the sweep gas from the irradiation cell to pass through the gas sample loop to the flowmeter. Valve I1 is closed to the sweep gas. When the sampler is in the energized state, valve I is closed t o the carrier gas but valves I11 and I V are now opened to the carrier gas which purges the sample loop and carries the sample to the separation columns. Valve I1 opens to the sweep gas and prevents pressure from building up in the irradiation cell.
