264 



SCIENCE 



[N. S. Vol. XSXIV. No. 870 



tures and must be elucidated and vigorously 

 emphasized by the laboratory teacher. 



It is in this connection that Dr. Benner's 

 recent suggestion* is particularly valuable, 

 viz., that the pupil should keep his test-tubes 

 with their tests until the instructor can in- 

 spect them. If parallel tests are applied to 

 the individual members of a group (which 

 will be the case, if the preliminary drill con- 

 sists as stated by the present writer in the 

 third paragraph), the bases of separation can 

 be pointed out on the test-tube rack. If the 

 results of the tests are not preserved, the 

 quizzing instructor must make use of the 

 notes on these experiments or the pupil's 

 memory of the results. 



Many teachers think highly of the induct- 

 ive method as a means of imparting an under- 

 standing of the bases of separation. The most 

 consistent and extensive use of this method 

 known to the writer was made in the Uni- 

 versity of Nebraska by Professor John White.^ 

 After the pupil has made a parallel study of 

 the members of a group as to their behavior 

 toward a series of reagents he is required to 

 devise the procedure for himself. The prin- 

 cipal merit of the plan is that it makes me- 

 chanical work impossible and teaches clearly 

 the bases of separation. It needs to be closely 

 supervised and the average instructor would 

 regard it as too slow; moreover, the procedure 

 devised by the best pupils must be discarded 

 for the more perfectly developed procedure of 

 the high-class modern manuals. The writer 

 uses this inductive plan only in connection 

 with the first group studied (silver group). 



Fifthly, we must teach the chemistry (and 

 some physics) of the tests. A recent canvass^ 

 has shown that many consider qualitative 

 analysis invaluable as an agency for develop- 

 ing the pupil's knowledge of chemistry. 

 Whether or not we wish to utilize qualitative 

 analysis for this purpose, the knowledge of 

 the chemical and some other phenomena in- 

 volved in the tests is essential to an under- 



' Science, N. S., XXXIII., 778. 

 ' Compare White 's ' ' Exercises in Qualitative 

 Analysis," Holt & Co., New York. 

 V. Am. CJiem. Soc, XXXIII., 630. 



standing of qualitative analysis. The pupil 

 himself recognizes this as an attribute of a 

 good course and he fully appreciates it when 

 he finds himself learning his chemistry from 

 experimental observation instead of from the 

 book, much more truly than in general inor- 

 ganic chemistry. The chemistry of the tests 

 deservedly engages much of the teacher's at- 

 tention during the major part of the course. 



A sixth essential is to cultivate self-re- 

 liance from the start. The teacher and the 

 procedure are not mated if the pupil is al- 

 lowed to think that the procedure has many 

 loopholes or pitfalls whereby the learner may 

 be deceived. If the general procedure is really 

 weak at any point, a supplemental note should 

 appear in the procedure, dealing with the pos- 

 sible difficulties. Furthermore, the pupil must 

 be encouraged to rely on careful work and to 

 defend it against the teacher's suspicions. It 

 may even be justifiable to approve a presum- 

 ably incorrect report on a minor constituent 

 rather than let a conscientious student have 

 his faith in his work undermined, but the 

 need of taking this measure should seldom 

 arise. Recording the report of an unknown 

 in ink in the note-book is a splendid means of 

 developing reliable work. The pupil will seek 

 to clear up all doubts before he commits him- 

 self to an unerasable report. 



Self-reliant work by the pupil is quickly 

 discouraged by any knowledge or suspicion 

 that the instructor is guessing at the compo- 

 sition of an unknown. He must know exactly 

 what the pupil ought to find, which means 

 that the instructor's, or standardizing, analy- 

 sis should be made by the same procedure as 

 the pupil follows, since more delicate tests 

 would sometimes give a positive result not 

 yielded by another test. Any one who is fa- 

 miliar with qualitative laboratories must real- 

 ize that in precision of instruction they aver- 

 age far behind the mathematics class-rooms 

 or physical laboratories. 



In the seventh place, the pupil must he 

 trained in the proper handling of a miscel- 

 laneous concrete suhstance involving difficul- 

 ties of dissolving and of detecting major and 

 minor constituents. This is dealt with in the 



