ESSAYS 



SKETCH OF A LOGICAL DIVISION OF CHEMISTRY 



(Prof. Ingo W. D. Hackh, A.B., Ph.C, College of Surgeons, San 

 Francisco, U.S.A.). 



Increase in knowledge and the rapid unfoldment of natural laws renders 

 specialisation more and more necessary. Chemistry to-day permeates every 

 natural science, and is, as the science of matter, the corner-stone of all know- 

 ledge dealing with matter from the macrocosmos to the microcosmos, 

 astronomy to biology. Therefore the growth of chemical knowledge renders 

 it necessary to divide chemistry into many branches, a process which has 

 been going on especially during the last two decades. A uniform classifica- 

 tion is difficult, however, for the various factors and phenomena are not 

 always clearly understood, and not distinctly different in kind, but differ 

 mainly in degree. 



A classification, above all, must be practical, and it seems best to divide, 

 as far as possible, into three main branches : 



I. Theoretical Chemistry, 

 II. Practical Chemistry. 

 III. Applied Chemistry. 



These three branches represent, in general, the application of the maxim — 

 study every natural phenomena as to cause, appearance, and effect. Thus : 



Theoretical Chemistry is the study of the laws that govern chemical 

 changes — the doctrine of cause. 



Practical Chemistry is the observation and description of the phenomena 

 and chemical individuals, as well as a study of the composition of things — 

 the doctrine of appearance. 



Applied Chemistry is the utilisation of chemical knowledge for the welfare 

 of mankind, and may be termed the doctrine of effect. 



There are gradual transitions everywhere in life and nature, and nowhere 

 an abrupt change without connecting link. Between one extreme and the 

 other there are always found connecting tendencies, sometimes clearly 

 recognised, sometimes hard to distinguish. Sharp and clear-cut boundary 

 lines are not to be drawn in nature. Hence, the classification outlined 

 centres around principal factors ; everywhere are connecting links to other 

 centres, thus forming a complicated spacial structure interwoven with many 

 connections. The limits of a single branch are not so distinct and sharp 

 as the classification would let it appear. The table represents this classifica- 

 tion on a plane surface in which the connections and relations of the different 

 branches cannot be fully shown. 



I. Theoretical Chemistry 



The cause of every chemical phenomena appears to be the action of 

 chemical force in relation with physical energy. Omitting a discussion of 

 the nature of this force and energy, and without speculation on the structure 

 of the atom, there are the two factors : chemical force and physical energy. 

 Accordingly, the subdivision of pure chemistry and physical chemistry. 



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