I S D GSTRIAL AND EXGIXEERING CHEMISTRY
October 15, 1930
the box is made of brass and is of five essential parts-the female bushing, J, a lock nut, K , a soft-rubber gasket, L , a copper gasket, -71,and the male bushing, N . The female bushing extends through the bottom of the box. A thin rubber gasket is inserted between the hex-head of the bushing and the copper lining of the bath. Experience has shown that it is not satisfactory to solder this bushing in place, as even a slight expansion or contraction of the metal or a slight warping
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shoulder above the inside threads. The thin copper gasket, :If, is inserted between the rubber gasket and the male bushing to eliminate any twisting of the rubber gasket when the male bushing is tightened. The male bushing is tightened by hand, enough to compress the soft-rubber gasket slightly. The same method of sealing is used for the drain outlet through the bottom of the bath. Apparatus more or less common to the usual type of thermostatically controlled water bath was modified to meet the requirements of the “P.V.T.” problem. A useful device for supporting the apparatus in the bath is shown in Figure 5 . It is a snap clamp of flat spring brass. The use of this clamp permits any single one of the manometers to be removed from the thermostat for repairing or replacing without otherwise disturbing the other apparatus of the bath. ,Manomefer
Tube,
L
M
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Figure 4-Special Bushing for Sealing In Glass Apparatus
Figure 5-Device
of the box causes the solder to break. The lock nut, K , screv-s over the bushing from the under side to hold the female bushing rigid and to insure a water-tight joint. As shown in Figure 4, the inside of the female bushing is threaded more than half-way from the lower end. The glass end of the apparatus is inserted through this bushing with a clearance of inch (3.2 mm.) between the glass stem and the wall of the bushing. The soft-rubber gasket, L , fits snugly over the glass end of the apparatus and is pushed up to the
vsrass Sprmy C/amp
for Supporting Apparatus in Bath
The use of iron or other metals which are readily acted on by water is intentionally avoided in the construction of any part of the equipment which is immersed in water. The bath as described has functioned for many months continuously, and without special attention. Literature Cited (1) Bartlett, J . A m . Chem. SOC.,49, 687 (1927). (2) Bartlett. Cupples, and Tremearne. I b i d . SO, 1275 (1928).
Rinsing Pipets’ G . M. Kline BVREAUOF
STAKDARDS, T T A S I i I X G T O S ,
H E thorough rinsing of pipets after treatment with a cleaning solution is probably one of the most monotonous and time-consuming items in the cleaning of laboratory glassware. The writer has found the following method rapid and efficient for pipets of any size. Connect the pipet by means of rubber tubing to a water aspirator pump. Place the tip of the pipet under mater in a large beaker. To protect the tip allow the pipet to rest upon the side of the beaker. The upper end of the pipet can rest upon the edge of the sink and can be held in place by running the rubber tubing around a ring stand. Run a rapid stream of water from the tap into the beaker. Turn on the suction and allow the water to be drawn through the pipet for 2 minutes or until it is convenient to give it further attention. TWOminutes has been found sufficient to remove all traces of acid or alkali. Place the tip of the pipet in a beaker of distilled water and allow the pipet to be partly filled. Then, by withdrawing the pipet from the beaker and in1 Received June 6 . 1930. Publication approved by the Director of the U. S . Bureau of Standards, Department of Commerce.
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clining it with the tip up, this water is sucked through it. By repeating this operation the pipet may be rinsed efficiently with a small amount of distilled water. If one or more tees are connected to the aspirator line, a number of pipets can be treated a t one time. For narrow pipets of uniform bore, such as are accumulated in large quantities in bacteriological laboratories, the following method, described in Standard Methods of the Division of Laboratories and Research, New York State Department of Health, is undoubtedly a time saver: Place the pipets in a glass cylinder 450 by 75 mm. Hook over the nose a glass siphon about 14 mm. in diameter, reaching to the bottom of the cylinder. A 2-liter graduated cylinder can be used if the nose edge is sufficiently lower than the top rim to permit operation of the siphon. The current of water through the siphon is automatically made and broken, thus alternately emptying the pipets and allowing them to fill again. The flow of water through the siphon, of course, must be greater than the inflow of fresh water. By using tees several cylinders may be fed from one tap.
