September 1, 1911] 



SCIENCE 



263 



ing them of mental self-reliance and the 

 power to weigh evidence and think clearly. 

 Unless a change be made, chemistry will 

 surely earn a place among that group of 

 pedagogic processes which Huxley strove 

 so hard to have displaced, and which he 

 characterized as the direct and prevent- 

 ible cause of most of the world's stupidity. 



W. Lash MilijEr 



TEE GENERAL ESSENTIALS IN TEACHING 

 QUALITATIVE ANALYSIS 



The growing tendency to give more heed 

 to the methods of teaching the natural sci- 

 ences in the colleges has called forth the fol- 

 lowing generalizations regarding the second 

 course in chemistry. The pedagogical as- 

 pects of the first course have been ably dis- 

 cussed by many teachers. The abundance of 

 text-books on the second course, qualitative 

 analysis, seems to indicate that every teacher 

 follows his own notions and that no book is 

 very generally satisfactory, all of which is 

 unfortunate and perhaps unnecessary. There 

 are, however, certain principles that seem to 

 be regarded as essential by the majority of 

 thoughtful teachers and an eifort to present 

 these principles appears to be worth while. 



The main essential in conducting this 

 course is to teach qualitative analysis. It is 

 valuable and interesting on the side to 

 learn many reactions, but only those reactions 

 which are concerned in separations and 

 identifications can be considered essential to 

 the object in view. The study of other re- 

 actions is a study of general chemistry. 



Opinions differ as to what introductory 

 tests should be made by the beginner, but 

 the above principle is successfully carried out 

 when each individual substance (ion) is first 

 subjected alone to the same reactions which 

 it will undergo when present in a miscel- 

 laneous mixture under analysis. Such a 

 parallel study of the members of a group will 

 reveal' to the intelligent student the possi- 

 bilities of separation. 



Secondly, the procedure must he definite 

 and explicitly stated. Eecent experimental 



studies in testing qualitative methods, par- 

 ticularly those of A. A. Noyes and assistants, 

 have shown that the conditions of successful 

 work must be carefully studied out for each 

 step. Separations are very largely based on 

 solubility differences, which is a quantitative 

 matter; the directions must be devised with 

 this in view and must be full enough to leave 

 no room for doubt in the average mind. 



Accordingly, it is essential, in the third 

 place, that the printed procedure he con- 

 scientiously followed in detail. If varying 

 conditions make it necessary to add more or 

 less of a reagent in certain cases, the proced- 

 ure should give information; but when a pro- 

 cedure has been worked out on the basis of 

 elaborate qualitative and quantitative tests, 

 as have some of our modern procedures, a 

 pupil can not expect to get reliable results, 

 if he follows his own untutored discretion. 

 Analyzing from a memorized procedure is 

 indeed likely to be a dangerous undertaking, 

 since the memories of most young chemists 

 will be liable to lead them astray as to the 

 proper proportions or even the proper reag- 

 ents. It is not to be understood that the 

 procedure should be blindly followed, e. g., 

 with a false conscientiousness that would 

 lead the worker to filter a solution when no 

 precipitate was formed, but that those opera- 

 tions which are done should be conducted as 

 directed. 



In order that the pupil may be able to re- 

 produce the proper experimental conditions 

 for the tests, the pupil must be so carefully 

 trained in the art and language of manipu- 

 lation that he will have no difficulty in con- 

 ducting the operations as the author in- 

 tended. 



A fourth essential is to teach the hases of 

 separation. This is one of the most impor- 

 tant and difficult tasks of the teacher, for 

 much of the logic of the course is herein in- 

 volved. By bases of separation are meant the 

 difl^erenees in the physical and chemical be- 

 havior of substances which are utilized for 

 the purpose of separation. These are the 

 real "foundations of analytical chemistry." 

 They should be clearly presented in the lee- 



