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VOL. 11, NO. 10
INDUSTRIAL AND ENGINEERING CHEMISTRY
tube connecting the leveling bulb to the buret is replaced by short lengths of glass tubin connecting the leveling bulb to the buret and to the leveling &e. A stopcock is inserted between the leveling bulb and the leveling tube. Water a t a pressure slightly in excess of that required to raise the mercury to the top of the buret may be conveniently supplied through a reducing valve from the laboratory tap. Higher pressures than needed mi ht prove dangerous and would make manipulation difficult. &e water is led into the top of the leveling bulb through a three-way plug valve, the third side of which is connected to the drain. By rotating this valve through a 90-degree arc the direction of flow of mercury in the buret is reversed. At the center of the arc the mercury is held stationary. The ease and speed of manipulation depend to a large extent on the functioning of this valve. As a suitable valve was not available a t any of the equipment houses in the neighborhood of the author’s laboratory, a standard three-way 0.25-inch brass plug valve was remodeled. The plug was filled with solder and drilled to form an Lshaped port only 0.09 inch in diameter. A sli ht groove in the surface was tapered into each end of the drill hofe, as is sometimes done with glass stopcocks, to provide for a more readily adjustable flow. Grooves were then machined about the circumference of the top and bottom of the plug to provide for lubrication. As a lubricant, automobile water-pump grease was found superior to any of the common laboratory greases. All water connections were made with copper tubing 0.25 inch in outside diameter. Because of the mnre accurate control that may be maintained on the mercury level in the buret, it is possible to replace the conventional merrury manometer with one of water. This makes leveling off somewhat easier and increases the accuracy of the apparatus. The flow of water over the mercury in the leveling bulb serves t o keep the mercury clean, and it has not
been necessary throughout the analysis of over a thousand samples of mine air to provide any additional cleaning.
Operation Operation is similar to the conventional procedure except that the mercury is raised in the buret by passing water into the top of the leveling bulb instead of raising the leveling bulb. In leveling off, the mercury level in the leveling tube is adjusted to approximately t h a t in the buret. Then the stopcock is closed t o the leveling tube, the stopcock t o the water manometer opened, and the pressure balanced with that in a conventional compensating tube. After the operator is familiar with the apparatus, a n estimate of pressure may be obtained from returning the solutions in the absorption pipets to their original marks and the use of the leveling tube may be largely eliminated, affording an additional saving of time. This equipment, in addition t o saving time, takes much of the drudgery out of routine analysis b y eliminating the continual raising and lowering of the mercury-filled leveling bulb. It is particularly well suited to procedures that require a slow or even flow of gas, such as slow combustion.
Literature Cited (1) Blair and Purae, IND.ENQ.CHEM.,Anal. Ed., 11, 666 (1939). (2) Bonney and Huff, Ibid., 9,157 (1937). (3) Egerton, A. C.,and Pidgeon, L. M., J . Sci. I n s t r u m t s , 8 , 234 (1931). (4) Tauch, E. J., IND. ENG.CHEM.,19, 1349 (1927).
A Laboratory Lifting Device GEORGE CALINGAERT Ethyl Gasoline Corporation, Detroit, Mich.
M
ANY opera-
tions in the laboratory call for the lowering and raising of a heating bath, such as a n oil bath under a reaction flask or a still. This operation is normally accompanied by a decided hazard on a c c o u n t of t h e difficulty of handlingacontainer of FIGURE 1 hot oil, especially when it must be done quickly to prevent a reaction from getting out of control. A very simple device for doing this, which has been used in this laboratory for several years, is illustrated in Figure 1.
It ronsists of an automobile jack mounted on a late equipped with leveling screws which are long enough to enaele the plate to clear the base of a ring stand. The jack is equipped on top with a late approximately 20 x 20 cm. which is made to support the oirbath, with or without a hot plate, or any nther piece of equipment. Several makes and designs of automobile jacks have been tried out. The hydraulic type is unsatisfactory because it will not come down readily except with a large load, and also because raising and lowering require two different kinds of lever operation. The ratchet type is also unsatisfactory because an up-and-down lever operation might result in either raising or lowering, depending on the setting of the trip control lever. The preferred type is that calling for a rotary motion clockwise for raising and counterclockwise for lowering. The dreadnaught jack No. 26, 1-ton capacity, made by the Auto Specialties Manu-
W
FIGURE 2
facturing Company, St. Jose h, Mich., is suitable from the standpoint of size, stability, and &sign and gives a total lift of 15 cm. (6 inches). It is illustrated in Figure 1. Another jack of the scissor type, illustrated in Figure 2, has a lift of 23 cm. (9 inches) but is unnecessarily bulky for general operations where the smaller jack has sufficient lift. This type of lifting device has been found very satisfactory, not only for the repeated raising and lowering of heating baths, but also for the accurate control of heat that is required in fractional distillation.
