I AIDS FOR ANALYTICAL CHEMISTS Subdivision of Nonvolatile, Air- and Water-Sensitive Solids Sidney G. Gibbins Department of Chemistry, University of Victoria, Victoria, B. C., Canada
SUBDIVISION FOR ANALYTICALpurposes, etc., of large quantities of nonvolatile, air- and water-sensitive solids is accomplished by manipulation of the all-glass, grease-free apparatus shown in Figure 1. Absence of stopcocks permits prolonged operation with organic solvents. The apparatus is easily handmanipulated. The horizontal manifold, 14-mm o.d., is bent at 7 to avoid solute transfer to bulb 4. The fragile bulb sample tubes, 12-mm o.d., are approximately 14 cm long from the bulb to the constricted portion 8. Subsequently, a procedure, reference ( I ) , may be used to obtain weighed samples for analytical purposes. While possible in principle, the combining of these two procedures into one complex apparatus would likely be unmanageable. The bulk sample bulb A is sealed onto the sample subdivider B at 2. The apparatus is connected to a high vacuum line at the standard taper joint 3 and pumped down to less than mm Hg and flamed out. Additional solvent, if required, is condensed in bulb 4 (100 ml) by a cold bath ( I ) . After sealing off the apparatus at constriction 5 and breaking the fragile bulb 1 with a Teflon (Du Pont) coated bar magnet, an appropriate portion of the sample is transferred by solution and/or slurry manipulations to the fragile bulb sample tube 6. The constricted portion 8 of the tube is washed free of the solute by condensation of the solvent on the walls with, e.g. dry ice. After 6 and 4 are cooled to a temperature at which the solvent has negligible vapor pressure, 6 is sealed off. Freezing the solution in 6 should be avoided. The process is then repeated for each of the remaining tubes. (1) S. G. Gibbins, ANAL.CHEM., 43, 295 (1971).
1-5 cm
4
I 6
Figure 1. Sample subdivision apparatus
While failure of fragile bulb break seals is uncommon, it is good practice to flame out the end exposed to the atmosphere and seal it. This is accomplished by first necking the end down 10 and then collapsing the narrow orifice. Since region 9 is cooling during this process, the glass may suck in slightly. If bulb failure occurs, a minimal quantity of air is admitted. When the tube is to be used, the end is readily cracked off.
RECEIVED for review September 21, 1970. Accepted December 3,1970.
A Simple Spectrophotometer Scale Expander Emanuel P. Manche Division of Natural Sciences and Mathematics, York College of The City University of New York, Flushing, N . Y . 11365 SCALEEXPANDERS are useful in spectrophotometric work to expand a desired portion of a trace for better readability and identification of spectral details. Commercially available scale expanders are normally intended to be used with instruments which have a potentiometric output. The present paper describes a simple scale expander that is most useful with instruments that do not possess a potentiometric output to drive recorders. For this work a Perkin-Elmer Model 700 infrared spectrophotometer was used. This automatic recording doublebeam instrument features optical null. The trace is normally made with a pen linked to a servomotor which positions a linear optical attenuator in the reference beam to achieve null.
The recorder carriage is driven by the wavelength scan system with no provision for scale expansion. Construction Details. The scale expander consists of a few components which are readily obtainable in the laboratory, these being a mercury battery, a current adjusting pot in series with a slidewire, a switch, and a wiper contact. The electrical schematic is shown in Figure 1. Slidewire A-B was constructed by winding several hundred turns of 0.10-mm nichrome wire on a 4-mm diameter plastic rod, and then mounted on the scale support of the spectrophotometer. The wiper contact functioned best if made of a metal rod hinged on one side to the instrument pen. Also, provision had to be made to assure that the pen itself would not rotate ANALYTICAL CHEMISTRY, VOL. 43, NO. 4, APRIL 1971
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