J. B. Polya University of Tasmania Hobart, Australia
Microchemical Applications of the H-Flask
T h e distillation apparatus of Lieb and Schoniger' is useful both in micro and semimicro organic preparat,ions, but it is too specialized and relatively fragile for general use in a junior laboratory. A sturdier and more versatde modification, the H-flask, is suitable for the purposes of demonstration and practical work a t a more advanced level. The drawing sho~rsthe H-flask with dimensions that have been found satisfactory in practice. The construction is simple and should not be beyond the skill of students used to the elementary techniques of working with glass. Alternatively, an experienced glass blower can supply the requirements of a normal class within a few hours.
I n the simplest way the H-flask can be used for dist,illation from bulb A to bulb D, the stopper (crosshatched) may he replaced by one bored t o carry a thin t>hermometer. The narrow tube E acts as an efficient condenser for moderately volatile distillates in small amounts; it can be provided with an "anti-slug" hole.% For more efficient cooling, tube C i s immersed in a test tube filled with cold water; the apparatus can be held by the test tube, using one finger resting on the bridge B to guide the bulb A into the flame of the microburner or away from the heat. Increased condensation through slowing down the passage of vapors can he achieved also by inserting the dropper F into E. Cooling with the help of the internal tube can be used also to boil the contents of D under reflux. When fitted with a small round of filter paper hacked by a moderately tight wad of glass wool, E may be used as a
' LIEB,H., AND SCH~NIGER, W.,Mikmchem., 34, 336 (1949).
'STOCK,J. T.,
AND
FILL,M. H., J. CHEM.EDUC.,30,
(1953), Fig. 12.
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filter stick. Two layers of immiscible liquids in C arc separated or unmixed layers of miscible liquids built up with the help of the dropper F introduced t,hrough 8, which protects the micropipet against contaminat,iori with t,he unwanted phase. A mct,allic spiral wound around a glass rod replacing E makes a useful fractioilat,ingcolumn. If D is charged wit-h a drying agent and suction is applied to I
