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INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 12, NO. 4
FIGURE 6. Box ASSEMBLED, SEAMS WELDED
This panel may be used for the control of two heating elements connected in parallel with the common lead by plugging in the middle threepole convenience receptacle, or the two left-hand autotransformers may be used independently with three- ole attachment plugs by plugging in the left-Rand and the right-hand three-pole convenience receptacles. The right-hand autotransformer cannot be used with a three-pole convenience receptacle but onl\ with a two-pole polarized attachment plug. The three autotransformers may be used on a three-circuit heating system with a common lead-that is, a star hookup-by using a fourole attachment plug and the four-pole convenience receptacle fvhen an autotransformer is used to control a heating element from one convenience receptacle, it cannot be used for the control of another heating element from another of the convenience receptacles-that is, the middle autotransformer cannot be used to control a heating element from terminal 2 from the middle three-pole convenience receptacle and also a heating element from the right-hand three-pole convenience receptacle. The panels in these laboratories are made of 16-gage black iron. Wood may be used, but it is not recommended because of fire hazards present where fractionating equipment, boiling point apparatus, etc., are used. The developed view of the panel for the hookup shown in Figure 3 is shown in Figure 5 . The iron is bent along the dotted lines and seam-welded into the assembled box (Figure 6). The photograph of this finished panel is shown in Figure 7 .
Discussion The control panels as described should meet the needs for heat control in practically all cases encountered in the laboratory. Three autotransformers are the maximum that may be
FIGURE 7. PHOTOGRAPH OF FIKISHED PAKEL
built into a portable panel without making it cumbersome and heavy. However, there is no reason why four, five, or six instruments cannot be connected to give the maximum utility by elaborating the diagrams as given. The autotransformer allows the jacket temperatures of fractionating columns to be adjusted a t any temperature desired to within the precision of the jacket thermometers (0" to 360" C.) or thermocouple potentiometer. I n well-insulated apparatus the rate of boiling of solvents has been adjusted to within 1 per cent of the desired rate in terms of drops per minute or milliliters per hour. I n the evenings when the voltage is constant the rate has been adjusted to within 0.5 per cent. Acknowledgment The author wishes to acknowledge the assistance of Wallace Kinser and Otto Dickey, Electrical Engineering Department] in developing the heat control panel. Literature Cited (1) Morey, G. H., ISD. ENG.CHEM.,.4nal. Ed., 10, 531 (1938). PRESENTED before the Division of Physical and Inorganic Chemistry a t the 08th Meeting of the American Chemical Society Boston. Mass.
Removal of Adhered Rubber Stoppers
I
N T H E Analytical Edition of INDUSTRIAL ASD EKGIXEER- drop or tn-o of water is introduced between the glass and the rubber at the point of insertion of the file, the subsequent ING CHEMISTRY for January 15, 1940 (page 5 2 ) , there apremoval of the stopper is very greatly facilitated. peared a note by A. J. Bailey on the removal of adhered rubber F. A. Robinson, Glaxo Laboratories, Ltd., Greenford, stoppers. Shortly thereafter two readers called our attenMiddlesex, England, states that the tion to the similarity between this note and one by Lynn D. method is not without risk to the therWilson which appeared in the Sovember, 1939, issue of the mometer, \Thereas the following method Chemist-Analyst. is even simpler and there is little risk of It has been ascertained that hfr. Wilson's note reached the accident : Chemist-Analyst some months before bfr. Bailey's note was received here, but, as pointed out in the latter, i t seemed Moisten with glycerol or sodium hydroxide inevitable t h a t this method had been known and used. Rfr. solution the end of a cork borer slightly larger Bailey merely wished to emphasize its unusual effectiveness in diameter than the thermometer or tubing to be removed. Slide the cork borer over and the motive in publishing the note was to make it generally the end of the latter and rotate it slowly available to chemists] since i t had served the author and his while applying gentle pressure. The rubber fellow research men so satisfactorily. is forced away from the glass in preference It is unfortunate that neither Mr. Bailey nor any of those t o being cut through by the cork borer, which gradually passes through the hole in the through whose hands the note passed saw the previously pubstopper, leaving the thermometer free. I t lished note by Mr. Wilson. may be necessary to apply fresh lubricant hl. Parkin of the University of Sheffield, England, advises t o the cork borer from time to time. The us that he has used the method for 20 years and that if a accompanying diagram illustrates the idea.
