ANALYTICAL CHEMISTRY
2002 rupted gap, as the objective is to deionize the gap and maintain a constant dielectric. However, recent tests have indicated that ultraviolet irradiation of a tandem air-interrupted gap results in a distinct increase in stability and extends the period between resurfacing of the gap electrodes by a factor of 2.
front slide, except that in place of the regulating screw it has a coil spring (not shown) to maintain the slide in oontaot with the glass strips to prevent escape of the coating mixture. In use, a glass strip is inserted in place on plate F and under the hopper, the mixture is poured into the hopper, and then by pushing each strip through from back to front with the following one, satisfactorily coated strips are removed from the other end. The apparatus is constructed of stainless steel and is put together with soldered joints. Plates F and C are 0.072 inch thick and the rest of the apparatus is constructed of material 0.02 inch thick. A modification of the coating material used in the original strips was necessary because of the need for a starch-silicic acid mixture that would flow readily through the apparatus and still give a smooth-finished product that would develop in the various solvents in minimum time. It was found that either Clinco 15 starch or a 240-1 mixture of ordinary cornstarch and Superior A.4 tapioca flour produced the iixture.
Figure 1. Apparatus for Preparing Chmmatortripe Reproducibility studies on sir models of air-interrupted spark sources has demonstrated that the normal variation of 5% in the transmittance of the line image for au internal standard line could he reduced t o less than 2%. Routine error of meamrement on one material, which was normally 2%, was improved to 1%. In general, the greatest improvement was noted in the case of inexperienced technicians.
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A General Electric germicidal lamp (G4T4/1), complete with ballast transformer (GE 899435) and starter, shown in the figure, is mounted as an assembly with the tip of the tube approximately 1inch from the electrode. The current requirement is 0.2 ampere a t 110 volts. The charging cycle pattern on the cathode ray oscilloscope in the excitation source unit readily indicates electrical instability, and may thus be utilized to obtain correct positioning of the ultraviolet lanip.
Apparatus for the Preparation of Chromatostrips John M. Miller and J. G. Kirchner, Fruit and Vegetable Chemirtry Laboratory, Western Utilization Research Branch, Agricultural Rerearch Service, U. S. Department of Agriculture, Paradeno 5, Calif. N USINQ
the chromatostrips of Kirchner, Miller, and Keller
I [ANAL. CHEM.,23, 420 (1951)1, a method was developed for
coating the glass strips with the adsorbent mixture more rapidly t h m could he accomplished by hand. Figure 1 shows the apparatus that was constructed for this purpose, and Figure 2 shows how the parts are assembled.
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-mm-....,ly of Parts
The coating mixture was prepared by heating 3 grams of starch, 57 grams of Merck's reagent grade silicic acid, 700 mg. each of Du Pont's zinc-cadmium sulfide and zinc silicate, and 115 ml. of water on a water bath with stirring until the temperature of the mixture reached 70" C. It was then cooled with stirring to 30' C. and additional water was added if necessary to produce a mixture that would flow properly. Different batches of silicic acid may require more or less water. ACKNOWLEDGMENT
The authors wish to ackhwledge, with thanks, samples of I . M. Newton starches from Stein, Hall and Co., Inc., and from . of Clint.0" Foods, Inc.
