A Small Portable Air Compressor Suitable for Laboratory Use G. F. FLEMONS, Government Chemical Laboratory, Suva, Fiji
THIS
unit was evolved to meet the requirements for compressed air and partial vacuum called for in the normal laboratory. I t s construction is simple and is well illustrated by the accompanying photograph. THE COMPRESSOR. B very satisfactory compressor unit can be obtained from a refrigerator, the one illustrated having been removed from a discarded Kelvinator. It is fitted with a differential valre on the suction side, thus a l l o ~ ~ i nany g degree of vacuum to be employed without affecting the operation of the compression side by the restriction of the air intake.
cluded, but i t is recommended that in this case a mercury make and break should be employed, as this method will provide for trouble-free operation. GENERAL CONSTRUCTION. The components are mounted, as shown. upon a strong baseboard fitted with swiveling rubber-tired wheels. This allows for ease of movement and also eliminates practically all vibration. The applications to which this unit can be put are varied and include the operation of the Hortvet cryoscope.
Acknowledgment The author is indebted to the Government Chemist for permission to publish. RECEIVEDSeptember 1, 1937.
A Reflux Bath Agitator for Low-Ternperature Fractional Distillation Analysis Columns J. V.TOOKE Phillips Petroleum Company, Bartlesville, Okla.
T
HE usual methods of agitating the reflux bath of low-
temperature fractional distillation analysis columns are not adequate in that too great a temperature difference exists between the top and bottom of the bath. This is especially true during and just' after the introduction of liquid nitrogen into the expander. I n order to overcome this disa d v a n t a g e t h e agitator herein d e s c r i b e d h a s b e e n designed. The greatly increased circulation of the cooling bath liquid permits no perceptible temperature differential, t h u s e n s u r i n g b e t t e r column control and sharper cuts between fractions. T h i s a p p a ratus also reduces vapor hazards to a minimum.
AIR COMPRESSOH UNIT
MOTOR. The power of the motor will depend upon the output of the compressor and the amount of pressure required Transmission is by means of a refrigerator belt, but the ordinary V-fan belting used on automobiles would prove equally satisfactory. Any convenient method of adjusting and maintaining the tension of the belt can be incorporated, but i t has been found that a trouble-free system is obtained by pivoting the motor on one side of its base and allowing it to tension the belt by its own weight. PRESSURE CYLIXDER.The steel drum and fittings were taken from the benzoline-injection system of a Braun assay unit. Any suitable type of gas bottle could, however, be used. The air connections and needle-valve controls can be seen in the photograph. An adjustable blowout ralve of the spring-loaded ball type provides for the maintenance of a fairly constant pressure in the cylinder. I n the compressor unit described here, no electrical cutout was employed, as the mechanical device has proved remarkably satisfactory, maintaining a pressure of 30 pounds per square inch with a divergence of approximately 1 pound. An automatic electrically operated cutout of the diaphragm type could be in-
To a standard liquid nitrogen evaporator are soldered two bearings, one at, the top and one at the bottom as illustrated. These bearings carry a I-mm. steel shaft to x-hich have been soldered three down-pitch impellers 5 to 7 mm. in diameter, made of thin sheet metal. The shaft and impellers are p r o t e c t e d by a quarter-circular, thin sheet-metal shield, which also serves to hold the apparatus snug within the bath. Motive power is supplied by a small induction-type nonsparking motor or air turbine, neither of which produces an appreciable vibration. RECEIVED March 3, 1938.
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