April, 1923
INDUXTRIAL A N D ENGINEERING CHEMISTRY
"chattering" of the relay is to put an 8-microfarad condenser, CB,in parallel with the windings of the relay. This method works as well as the first on direct current, but is much more expensive and, moreover, it cannot be used with alternating current . For a 60-cycle, 110-volt, alternating-current supply the circuit as given in Fig. 1 can be used if the condenser C is eliminated and a 1.0 microfarad condenser, C3,is connected in parallel with the windings of the relay. If this condenser is not used the relay will chatter, no matter what the grid leak may be. With this added condenser the relay can be operated just as satisfactorily with alternating as with direct current.
THERMOREGULATORS USED Several different kinds of thermoregulators were used with the foregoing controlling device to test the constancy of regulation over long periods of time. The first one used was made of 0.7 cm., Pyrex glass tubing bent in the form of a spiral just large enough to fit inside of a 12-liter bath. A small Utube containing a capillary of 1.5-mm. bore was sealed on the upper end of the spiral. After sealing the lower end of the spiral it was filled with toluene or turpentine (turpentine gave satisfactory results a t temperatures up to 70" C.) and the Utube filled with mercury. A small platinum wire sealed in the lower end of the U-tube was used t o make one contact, while a fine iron or nickel wire was used to make the adjustable contact in the capillary. By using iron or nickel wire any back-lash at the mercury contact is eliminated, because neither of these metals is wet by mercury, with the result that the temperature of the make is the same as for the break. Either iron or nickel wire can be used in the thermoregulator when the vacuum-tube controlling mechanism is used, without in the least decreasing the constancy of regulation, as there is no arcing and consequently no corroding of the contact point. If a platinum wire is used in place of the iron or nickel, the temperature of the make is higher (0.002' to 0.003') than that of the break. After filling the tube it was placed in the thermostat and then wired to the support of the stirring motor in such a way that the vibrations of the support were transmitted to the regulator. I n this way the regulator was given a periodic vibration which caused the mercury surface to oscillate uniformly. It-was found that a moving mercury surface gave very sensitive temperature control (within += 0.001 '), and it has an added advantage over the oscillating point in that it requires no extra equipment. With the spiral thermoregulator connected as described and containing 125 cc. of toluene and 25 cc. of mercury, the temperature of a lZliter, asbestos-jacketed, glass jar was maintained a t 25" * 0.001" C. for a period of 3 mo. under varying room temperatures. These readings were started after the regulator had been in use for 2 wks. When this thermoregulator was operated under the conditions described above, with the exception that it was suspended so as to prevent the mercury from jarring, the temperature variation was 25" * 0.02' C. With the toluene in the thermoregulator replaced by turpentine, the temperature of the bath was maintained a t 70" += 0.02' C. with the oscillating surface. Without the oscillating surface the temperature variation was 0.15' C. From these results it seems that the method of securing an oscillating contact by means of a moving mercury surface is as satisfactory, as far as temperature regulation is concerned, as Gouy's oscillating-point method. It is hardly necessary to emphasize the fact already pointed out in previous papers,'o that accurate temperature control depends nearly as much upon adequate stirring, proper distribution 10
Geer, J . Phys. Chem., 6 (1902), 85.
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of heating units and good thermal insulation as it does on a sensitive thermoregulator and proper controlling mechanism. While a glass thermoregulator gives excellent results when the room temperature does not fluctuate too greatly, a more rapidly acting thermoregulator is necessary when the room temperature fluctuates 5" or more from the bath temperature. It was found that a Monel metal tube filled with mercury responded more rapidly to temperature changes than did a glass thermoregulator of similar design. A thermoregulator was made of 152 cm. of Monel metal tubing 0.7 cm. in diameter and containing about 70 cc. of mercury. In order to take care of the electrical contactp, it was necessary to fasten a glass capillary to the Monel tube. After trying several cements to seal the glass to the metal with no success, we finally succeeded in making a tight joint by nickel-plating the two parts together. The glass was first etched for a length of 3 cm. and then coated with a silver mirror. The mirror was coated lightly with copper, and the glass tube, which just fitted inside the metal tube, was soldered in place. The joint was then plated with a thin layer of copper and this was coated with a heavy layer of nickel. This layer is approximately 1 mm. thick and consequently the nickel sheath is strong enough to hold the glass tube rigidly in place. This regulator maintained a 300-liter bath constant to within 0.001 ' even when the room temperature was 29" C., and a cooling coil was necessary. I n addition to its greater sensitiveness, a Monel metal regulator is very resistant to corrosion and breakage, and is therefore the most satisfactory for use in a water or oil thermostat under the usual laboratory conditions. N e w Section at. Akron The need for an Akron Section of the AMERICAN CHEMICAL SOCIETY has been felt for some time, since there are more than two hundred chemists in the vicinity, a large percentage of them being engaged in problems relative to the rubber industry. They accordingly felt the need of getting together regularly and bringing in speakers from the outside, who would talk to them and present problems that were confronting other chemists engaged in other lines of chemical work. On May 3, 1922, the chemists of Akron entertained the members of the Cleveland Section in Akron. E. F. Smith addressed the meeting, which was attended by about three hundred chemists. Talks were also made by C. I,. Parsons and H. E. Howe. The meeting was such a decided success that work was immediately started by the men located in Akron toward the formation of an Akron Section. These efforts were culminated on January 18, 1923, when an organization meeting was held and the following officers were elected : Chairman: W. W. EVANS. Vice Chazrman: N. A. SHEPARD. Secretary-Treasurer: W. J. KELLY. Councilor: R. P. DINSMORE.
The Akron Section extends an invitation to all members of the AMERICAN CHEMICAL SOCIETY to visit with them at any time they may be in the vicinity and meetings are being held.
Plans for Organization of Scientists i n N o r t h w e s t A meeting of people interested in the advancement of science was held in Spokane on February 9, and was attended by representatives from the science faculties of Washington State College, University of Idaho, State Normal School a t Cheney, Whitworth College, Spokane University, North Central High School, and the Lewis and Clark High School. After discussion which brought out the need of an organization with a meeting center in the northwest, a committee was appointed consisting of Dr. M. A. Angell, of Idaho University; Dr. Frederick Heald, of Washington State College; Dr. Geo. W. Hess, of Whitworth College; Miss Elizabeth I,. Martin, of Cheney State Normal School; Supt. 0. C. Pratt, of the Spokane public schools; and Mr. Frederick Keffer, mining engineer. Letters have been sent out to a large number of scientists residing in the district, asking suggestions as to the type of organization which would best serve the interests of the region.
