978 



SCIENCE 



[N. S. Vol. XXXI. No. 1 



for the college entrance requirement; our 

 course will not require us to cover so much 

 material as it did formerly. Discussion of 

 the rare elements and their compounds will 

 give way to a more intensive study of those 

 that show typical chemical actions, and 

 establish the main lines of thought. We 

 shall prefer to do this by reference to the 

 things of the practical life where we can, 

 but we will not go into the chemistry of 

 foods, dyes, textiles and the like, knowing 

 that this matter is far too complex for us 

 to use in establishing the laws and rela- 

 tionships that are necessary for a compre- 

 hension of the science. We shall draw 

 from every aspect of chemistry in our effort 

 to establish the principles of chemical ac- 

 tion. Our teaching may grow less de- 

 scriptive and more dynamic. We may find 

 it better to study types of chemical action 

 than to study elements and compounds. As 

 suggestion along this line, we might pro- 

 ceed, after reaching the definitions of 

 chemical action, element and compound, to 

 the general study of simple decompositions, 

 using many experimental illustrations. We 

 would bring in the ideas of stability and 

 heat of formation. We would then pro- 

 ceed to direct combinations, simple replace- 

 ments, and so on until finally the pupil 

 would have a very good idea of the com- 

 paratively few types of chemical action. 

 He would acquire incidentally a very prac- 

 tical descriptive knowledge. 



Our course will necessarily continue to 

 pay a large amount of attention to chem- 

 ical theories, in order that we may have the 

 means of seeing analogies and intei'preting 

 results. The mechanism of chemical 

 changes is so far removed from direct ob- 

 servation by the senses that any attempt 

 to comprehend these must be largely by 

 aid of the imagination. The atomic theory 

 has given us a splendid instrument for this 

 purpose. We should retain it even if it 

 had done nothing more than give us a svs- 



tem of chemical formulas, or made it pos- 

 sible to represent chemical actions by equa- 

 tions. Only one who has attempted to 

 teach chemistry without the use of these 

 symbols can fully appreciate what a tre- 

 mendous aid they are. We shall therefore 

 want to establish the atomic theory ration- 

 ally, and to show how formulas are deter- 

 mined. This is perhaps the most difficult 

 part of our work, but the fact that many 

 pupils fail utterly to comprehend this mat- 

 ter is no ground for its omission from the 

 course. There are many who succeed, and 

 we must not forget that those who fail at 

 least learn that such knowledge was ac- 

 quired by human reasoning and patient 

 experimenting. We should make our 

 pupils feel that these theories are very 

 practical things indeed, since it is largely 

 by their aid that the science has advanced 

 and brought material benefits to mankind. 



We have in the past been given to con- 

 siderable drill in certain types of chemical 

 problems, largely because of the demands 

 of college entrance examinations. There 

 has been a good deal of mental gymnastics 

 in the matter. These calculations should 

 be taught in a less formal way ; the labora- 

 tory is the best place to do it. Let the 

 pupil calculate from the equations the 

 quantities of substances he needs for 

 his reaction, and then actually mix them in 

 these proportions. Let him get practise in 

 correcting gas volumes in the course of ex- 

 periments involving simple gas measure- 

 ments. Knowledge acquired in this way 

 has a far greater staying quality than that 

 obtained in formal class-room drill. 



As we have already said, chemical tech- 

 nology will find a place in the course, but 

 it must be taught by principle too. In the 

 Solvay process, for example, it is more 

 important that the pupil should get the 

 idea of precipitation by differences in solu- 

 bility than that he should know the me- 

 chanical details of the carbonating towers. 



