108 CHEMICAL DISCOVERY AND INVENTION 



part of hydrogen combined with eight parts of oxygen, and that 

 no matter from what source it is procured it always has exactly 

 the same properties, the same colour, the same boiling point, the 

 same freezing point. If different samples of natural water seem 

 to differ one from another, as for instance, rain water from river 

 or sea water, this is merely due to the presence of other substances 

 dissolved in it, and which by well-known methods can be separated 

 from it, leaving the water unchanged. 



Another important law in chemistry is the Law of Multiple 

 proportions discovered by John Dalton, and illustrated and 

 explained by his famous Atomic Theory. 



The question whether matter is capable of division and sub- 

 division ad infinitum, or whether there is a limit beyond which 

 the particles are so hard that no power in nature is capable of 

 breaking them into smaller pieces, is one which has been debated 

 from the earliest times. 



The vague atomic hypothesis of Democritus was the subject 

 of fruitless debate in the Middle Ages. Newton in expounding 

 his gravitation theory, which is applicable to the smallest particles 

 of matter as well as to suns and planets, gave expression to the 

 view that in the beginning matter was formed of " solid, massy, 

 hard, impenetrable, movable particles, "and that " those primitive 

 particles being solids are incomparably harder than any porous 

 bodies compounded of them ; even so very hard as never to 

 wear or break in pieces." But it was reserved for Dalton to 

 supply that basis of fact without which every hypothesis is 

 useless. How the theory was established is explained in the 

 best text-books. It will be sufficient here to give in Dalton's 

 own words an enunciation of the modern doctrine. 1 " Chemical 

 analysis and synthesis go no farther than to the separation of 

 particles one from another and to their reunion. No new creation 

 or destruction of matter is within the reach of chemical agency. 

 . . . All the changes we can produce consist in separating particles 

 that are in a state of cohesion or combination, and joining those 

 that were previously at a distance." If, therefore, there are two 

 substances which can combine, say nitrogen and oxygen, their 

 union can only occur between whole numbers of atoms, such as 

 one atom of nitrogen to one atom of oxygen, one atom of nitrogen 

 to two atoms of oxygen, or two atoms of nitrogen to one atom 

 of oxygen, etc. 



1 Dalton" s Chemical Philosophy, 1808, Vol. I, p. 11?. 



