An Improved Capillary Clamp HERBERT K. ALBER, Biochemical Research Foundation of t h e Franklin Institute, Philadelphia, Pa.
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S bIASY microchemical procedures it frequently becomes necessary to measure the diameter of glass tubing or capillaries-the test tubes of the microchemist-with a high degree of accuracy. T o make this measurement, the object is placed vertically in the optical axis of the microscope and the diameter is determined with a previously calibrated micrometer eyepiece. If such measurements are made frequently-in routine analyses or in courses on microtechnic (8, 4, 6)-the use of a special capillary clamp is recommended which facilitates the mounting of the object, Such holders have been described ( 2 , 4, 5 ) ; Figure 1 shows an improved design. (This capillary clamp is obtainable from the Arthur H. Thomas Co., Philadelphia, Pa.)
FIGURE1 The advantages of this inexpensive clamp of nickel-plated brass over previous forms are as follows: The heavy trapezoidal base plate stabilizes the clamp, so that the tendency towards tilting is considerably reduced, even if heavier objects have to be supported, such as Pregl’s absorption tubes, in which the dimensions of the capillary endings must be accurately verified (2, p. 227). The dimensions of this base plate are chosen in accordance with the average dimensions of t,he ordinary rotating microscope stages. The side screws allow a fine adjustment of the pressure exerted by the spring clamps against the capillaries. Objects of different diameters are held safely; the single groove on the back (Figure 1) has a diameter of 2 mm. and serves to clamp tubes of diameters up to 10 mm.; the 3 fine grooves, 0.8 mm. in diameter
and thp same didance apart, hold smallcr objects of diameters below 2 mm. As the spring exerts only a slight pressure against the horizontal arm, which is 13 mm. high and 4 mm. thick, thinwalled capillaries, 0.3 mm. or less in outside diameter, are not bent, a condition which rrould interfere wit’h the passage of the light bcam, at least in some instances. For extremely fine objects, such as fibers, capillary rods, etc., a thin piece of rubber sheet is placed over the grooves as a cushion. The spring clamps are easily renewed if they lose their elasticity. The numerous possible applications include: determination of the bore of capillaries used for all qualitative experiments (4, p. 36; 5 ) ; observation of the color of liquids in capillaries (coloriscopic capillary, 2, p. 226; 4, p. 93; 6); comparison of three colors by means of the three grooves, thus eliminat’ing any doubtful observations in sensitive color tests where the reagent itself has a slight color (blank tests in Feigl’s spot tests) ; standardization of capillary pipets used in Emich’s schlieren experiments (4, p. 46; 5, p. 40); holding of needle electrodes during the observation of metallic deposits; and control of further manipulations (1; 2, p. 236). Recently (S), this clamp has rendered excellent service in determining the extremely small bore a t the fine tip of weighing capillaries used when liquids of high vapor pressure or high hygroscopicity are to be weighed for quantitative milligram procedures. According to the experience of the author, the bores must be within the range of 0.03 to 0.05 mm. to prevent any evaporation or moisture absorption during the weighing procedure, since these capillaries should not be sealed.
Literature Cited ( 1 ) Alber, H. K., Jeinkontorets Ann., 116, 519 (1932). (2) Alber, H. K., M i k r o c h e m i e , 14, 219 (1933/34). (3) Alber, H. K., Ibid., in press. (4) Benedetti-Pichler,A. A , and Spikes, 7.7‘. F., “Introduction to the Microtechnique of Inorganic Qualitative Analysis,” Douglaston, N. T., Microchemical Service, 1935. (5) Emich, F., and Schneider, F., ”Microchemical Laboratory Manual,” New T o r k , John Wiley &. Sons, 1932. RECEIVED March 29, 1938.
A “Long Burner” Adapter for Bunsen Burners ALEXANDER KNOLL
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JOHN SCHUKAL, Department of Chemistry, Columbia University, New York, N. Y.
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HE adapter pictured here fits over the barrel of a Tirrill
or other type of Bunsen burner, and may be used in place of t h e common “long burner” in the micro and semimicro combustion methods of ultimate organic analysis and for bending glass tubing of large diameter. It is inexpensive and easily regulated as to size of flame and height. It will burn natural gas and water gas satisfactorily. It consists of a brass pipe of standard 0.094-inch stock, i inches long and 1 inch in outside diameter. The ends of the pipe are closed flush by means of two brazed caps. Two rows of thirty-six holes 0.056 inch in diameter and 0.19 inch apart are drilled along the top of the burner piece. The barrel, of 0.094-inch stock is 4.5 inches long and about 0.5 inch in inside diameter. It is threaded and soldered into the bottom of the burner piece a t the center. A set screw near the bottom of the barrel allows adjustment of the height. RECEIVED March 8, 1938.
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