A MICRO GAS GENERATOR LOUIS C. W. BAKER .ad JOHN E. ST0UFPE:R Boston University, Boston, Massachusetts
shows a micro Iiipp generator for H2S which we have found more satisfacto~ythan any previously described. Several particular features must be observed. Precautions. Surface tension effects can he very pronounced in a micro apparatus and destroy the effectiveness of the hydrostatic head in producing gas pressure. The following must not be less than specified: (1) the clearance between the inner test tube wall and the outer wall of the gas tube (4 mm.); (2) the diameter of the hole in the bottom of the gas tnbe (3-4 mm.); (3) the clearance between the glass "nail head" and the inner wall of the gas tube (1.5-2 mm.). The use of glass wool in place of the glass rod makes for unsatisfactory capillary effects. The use of more than three or four chunks of FeS (each about 4 mm. in diameter) makes for unsatisfactory performance. Operation. The amount of HC1 (6 M) should be such that its level is approximately 1 in. below the larger rubber stopper when the inner tube is empty. For convenience in recharging, a mark should be made on the test tube designating the level to which this amount of HCI fills the test tube when the inner tnbe is removed. At the end of each laboratory period the renter tnbe is removed, rinsed inside and out under a tap, and stored separately. If any tiny pieces of FeS have crumbled away, they are all found in the bottom of the test tube. The students separate these by decanting the HCI into another container for storage. This generator was made by each student and used in a course where over 100 students used the laboratory daily. HaS fumes and generator operation completely ceased to be problems. With slight modifications the generator can be used for COz and other gases.
SLOT IN RUBBER
rBXl-IN. TEST TUBE 4 4 - M U . TUBING
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