AN AMMONIUM CHLORIDE "CHIMNEY" HARRY L. DAVIS and J. W. NECKERS Southern Illinois State Teachers College, Carbondnle, Illinois
THE accompanying photographs picture a very unusual manifestation of a very common occurrence in a chemical laboratory: the formation of ammonium
test tube half full of a solution containing considerable excess of hydrochloric acid. The next day the beautiful formation which is pictured resulted.
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chloride by the union of gaseous ammonia and hydrogen Apparently the ammonia concentration arouudlthe chloride. Chemical apparatus, particularly in laboratories for general and analytical chemistry, is very test tube was sufficientso that as the hydrogen chloride often coated with ammonium chloride and it is the sub- reached the top of the tube it immediately formed amject of numerous questions from beginning students. monium chloride, which was deposited on the lip. This reaction and deposition continued in the quiet atmosNever have we known it to take this form. This particular case occurred in a course in qualita- phere of the locker, with a very narrow zone of diffusion, tive analysis. An ammoniacal solution of Group IV until the illustrated "chimney" of very fragile salt was cations was left overnight in a laboratory locker to in- built up in successive rings to a height of nearly eighteen sure complete precipitation. Nearby, in a rack, was a millimeters.
