T. R. Williams and John T. stock The University of Connecticut
Storrs
I
A
csTesting Device Using
Liquids or Test Papers
Although tests for gases evolved during small-scale qualitative inorganic analysis are often made with a drop of reagent supported on the end of a glass rod, results are 1111certain in the hands of beginners or n~henthe concentration of gas is not high. The gas testing device shown in the figure is more satisfactory and may be constructed in a few minutes from 6-mm outside diameter glass tubing. 14 Rubber tubing sleeve A enables the device to be inserted directly into the mouth of the 10-mm diameter semimicro test tube from which the gas is to be evolved. By means of a finesimple g...te.ting tipped test pipet, 0.05 to 0.1 ml of a device. suitable reagent is introduced into bulb B and the appearance of the reagent is observed as the gas flows over its surface. Apart from its use with liquid reagents such as lime water, mixed bromine and barium chloride solutions, etc.,' the device will hold narrow starch-iodide, pH-
384 / journal o f Chemical Education
sensitive, and other test papers. Even dry papers are amply supported if thrust in far enough to enter the bend, as shown a t (a). Where deleterious to a test being carried out with a liquid reagent, spray carried up from the reaction mixture may be largely arrested by using a lightlytwisted narrow strip of filter paper in place of impregnated paper. Although to be used with caution owing to possible attack upon the central wire, a 30-mm length of pipe cleaner is a more efficient trap. This is pushed around the bend until the inner end is a few mm from the bulb. When wetted with a suitable absorbent, the pipe cleaner trap will qualitatively remove components of certain gas mixtures. Thus after absorption of carbon dioxide with sodium hydroxide solution, the carboil monoxide also evolved during the dehydration of an oxalate by concentrated sulfuric acid may be readily ignited at the outlet of the gas testing device. I
the
STOCK, J. T.,AND HEATH,P., "Small-scale Inorganic Qus1it:~.hslysis," Chemical Publishing Company, New York, 1954.
