CHEMISTRY 



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CHEMISTRY 



Only one-half of the elements in this list 

 are found in abundance in nature; the others 

 are rare. Thus, the earth's crust in the main 

 is composed of the elements oxygen, silicon, 

 aluminium, iron, calcium, magnesium, potassium 

 and sodium. Over ninety-eight per cent of the 

 -weight of the earth's crust is composed of the 

 above-mentioned elements. The chief elements 

 of the atmosphere are, as we have stated, oxy- 

 gen and nitrogen; those of water are oxygen 

 and hydrogen. 



Theories about the Elements. We have de- 

 fined elements as substances which are not 

 related to each other and which cannot be 

 transformed into one another. But let us state 

 here that since men began to think about the 

 "nature of things," as the Latin poet Lucretius 

 expresses it, they have always been inclined 

 to believe in the unity of matter. That is, 

 they were inclined to think that all the sub- 

 stances found in nature consist essentially 

 and ultimately of one and the same substance, 

 and that all of them are made of a single 

 primordial matter. The ancient Greek philos- 

 ophers believed that the universe and all that 

 is in it were formed by the combination of four 

 substances, namely, fire, air, water and earth. 

 They considered these as elements. The be- 

 lief in the unity of matter and in the trans- 

 mutability of the elements into one another 

 forms the basis of the teachings of alchemy. 



Modern chemistry is based, of course, on 

 other principles, and uses positive methods in 

 research and investigation. This explains the 

 wonderful advance this science has made dur- 

 ing the last hundred years; but the mind of 

 man will always find a special fascination in 

 trying to speculate about the origin of things 

 or the ultimate cause of things. There are 

 yet to-day many eminent men of science who 

 believe that all the elements are composed of 

 the same matter. 



The Electron Theory of Atomic Structure. 

 This view of the ultimate unity of the ele- 

 ments will be strengthened if the latest theory 

 about the structure of atoms proves to be cor- 

 rect. According to this theory the atoms of 

 all substances are made up of a great number 

 of electrons (see ELECTBON). The elements 

 vary from each other because their atoms are 

 composed of different numbers of electrons and 

 because these are grouped together in a number 

 of different ways. We know that the newly- 

 discovered element called radium has the 

 power of emitting continuously streams of free 

 electrons. We also know that radium is chang- 

 ing into the element helium, which is an ex- 

 ample of the actual transformation of one ele- 

 ment into another. But before any definite 

 conclusions can be reached on this as well as 

 on other similar subjects a great amount of 

 scientific work will have to be done. 



It is worth mentioning here that the spec- 

 troscope (which see) has shown that we find 

 in the sun and in the stars the same elements 

 as on earth, which indicates that the highest 

 temperatures existing anywhere in nature are 

 not capable of decomposing the elements. 



Chemical Compounds. The subject of com- 

 pounds in chemistry is a very interesting one, 

 for a chemical compound is a very different 

 thing from many of the substances which are 

 usually thought of as compounds. For instance, 

 one who eats a piece of cuke can say at once, 

 "There is sugar in this cake; there is butter; 

 there are flour and vanilla ; there are eggs." It 

 is one body a piece of cake; but it is also 

 very evidently made up of many substances. 

 That is, it is a compound, in the ordinary sense 

 of the word. 



There arc, however, other things which do 

 not announce so clearly their composite char- 

 acter. No one on tasting common salt would 

 think of it as a compound, and water seems 

 not in the least like two things, yet both of 

 these every-day substances are compounds. 

 They differ, however, very decidedly from such 



