A MODIFICATION OF THE STANDARD HIGH-SCHOOL EXPERIMENT ON THE DESTRUCTIVE DISTILLATION OF SOFT COAL
A method is suggested whereby the presence of ammonia in coal gas may be successfully detected. Lime is introduced into the coal-tar collector.
. . . . . .
I n order to detect ammonia as one of the by-products formed during the destructive distillation of soft coal, most laboratory manuals direct the student to place a piece of wet litmus paper over the mouth of the jet tube. The authors have found that this procedure invariMr;kd ably results in failure in that the litmus paper always turns red instead of blue. At the James Monroe High School, the followingmethod, which will be recognized as a variation of the customary commercial practice, FIGURE1 has been used with high success. The student is first directed to heat the bituminous coal in the standard apparatus (Figure 1) and to note the fact that tar and a combustible gas are formed. He is then told to put about ten grams of quicklime (or slaked lime) into the cod-tar collector and to continue heating. At this point, a FIGURE a ~ i e c of e wet litmus o a ~ eis r held in the path of the gas issuing from the jet tube and the student finds that the red litmus paper turns blue, indicating the presence of ammonia. The student will also find that the combustible DroDertv of the coal gas bas not been materially reduced by the absorption of the acids by HX). the lime. -R~~~~~~1 The aforementioned procedure may be varied by using one of the foUowing plans: (a) instead of merely using one test tube to collect the coal tar, two test tubes may be connected in series (Figure 2): the first test tube will collect the coal tar and the
.
u
A
.. .
--
150
VOL.8, NO.1
DISTILLATION OF SOFT COAL
151
second, containing lime, will collect the acidic vapors of carbon dioxide and hydrogen sul6de. (b) Instead of lime, sulfuric acid may be used in the second test tube (Figure 3). The acid, of course, will combine with the ammonia, which later can be driven off by heating with l i e . The presence of ammonia in coal gas can thus be very satisfactorily demonstrated.
