PART II
We have now made a rapid survey of the history of chemistry, and traced the evolution of thought which has rendered possible the newer conceptions of the constitution of matter. We must now say a few words as to the nature of the various elements themselves, and give a brief account of some modern researches. A few practical hints as to experiments may also be of interest to the reader.
We have seen that when two chemical elements combine, some third substance is formed, quite different in properties from the original two. Thus, water seems to us entirely different from the two invisible gases which compose it—oxygen and hydrogen. Yet a simple experiment will prove that such is the case. We can decompose water by means of an electric current, when the original gases are given off, in the proportion of two to one—hydrogen collecting at the negative pole, and oxygen at the positive. This process can be kept up until all the water has been decomposed, and only hydrogen and oxygen gases remain. This process of electrical decomposition is known aselectrolysis.