EXPERIMENT WITK HYDROGEN CHLOR~E VOL. 6, NO. 5 A DEMONSTRATION
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A DEMONSTRATION EXPERIMENT WITH HYDROGEN CHLORIDE CHARLES H. STONE, ENGUSH HIGHSCHOOL. BOSTUN, MASSACHUSETTS
Although the effect of hydrogen chloride upon the throat and nasal passages is much less irritating and disagreeable than that produced by chlorine, it is nevertheless unpleasant and should be avoided when possible. The apparatus shown below has been used on the demonstration desk in the writer's classes for a number of years with complete satisfaction. This apparatus entirely prevents the escape of hydrogen chloride into the air of the room and a t the same time illustrates several interesting phenomena. In the generator flask are placed about twenty-five grams of common salt, which is moistened with about five cubic centimeters of water. In the dropping funnel are placed about ten cubic centimeters of concentrated sulfuric acid. Bottle B is filled nearly full of water but bottle C is empty. The tube leading from the generator to bottle B should extend barely through the stoppers but the tube leading from bottle B to bottle C should extend nearly to the bottom of both bottles. There need be no stopper in bottle C. The attention of the class should be directed to these points and to the fact that the generator a t the beginning of the experiment contains air in addition to the salt and water. The stopcock is now opened and some sulfuric acid allowed to fallon the moistened salt. Action will be seen to take place. Presently the water in B will go over into C. When all the acid has been added and the stopcock is closed it will he seen, after the action in A has continued for some time, that the water in C flows hack again into B. The attention of the class should he directed to these changes and the explanation sought. When the action in A slackens, heat may be applied. The liquid in B may pass over again into C but will presently return to B. Careful examination of the liquid in the bottle will reveal the downward flow of the acid through the water. When no further action is evident in A after continued heating, the heat may be removed. The liquid in the bottles will finally remain in B. The liquid finally remaining in B may,now be examined and tested for its action on indicators, on zinc, and on solutions of silver, lead, and
mercurous nitrates. It should react vigorously with zinc but may not be sufficientlyconcentrated to react with oxidizing agents to form chlorine. If desired, the generator may be filled with water through the dropping funnel to absorb any gas remaining in the generator before emptying out the contents. The solution thus formed in A may be crystallized to obtain the sodium sulfate.
