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Page:Popular Science Monthly Volume 65.djvu/63

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or of the relation of the parts of an organism to one another there is obviously nothing in common between the observational deductions made in the biological laboratory and the quantitative measurements of the physical laboratory.

The divergence between the functions of the chemical and the physical laboratory is hardly less marked. While chemistry has irrefragable claims to designation as an exact science, the enumeration of the chief laws discovered up to the present is a simple matter and does not make a very imposing list. They are:

The law of the conservation of matter.
The law of constant proportion.
The law of multiple proportion.
The law of volumes or Avogadro's law.
The law of specific heats or the law of Dulong and Petit.
The law of periodic groups or Mendelejeff's law.
The law of electrolytic dissociation.
The law of isomerism.
The law of organic series.

It is, to say the least, a noteworthy thing that although these laws constitute the true claim of chemistry to be called a science and are moreover essentially quantitative in their character, practically no one ever thinks it necessary to the laboratory study of chemistry that students should carry out measurements looking toward even a rough verification of these laws, nor has the writer heard that the most enthusiastic advocate of the heuristic method has ever cajoled a student into thinking that he (the student) has discovered one of these laws by himself. The real fact which makes the laboratory study of chemistry a totally different one from that of physics is that the student meets even in the elementary stages a multitude of unfamiliar phenomena which can best be comprehended and learned by individual and intimate association with them, while there are altogether but two or three quantitative experiments which are available. In physics, on the other hand, the proportion is quite the reverse. The phenomena are, for the beginner, simple and entirely familiar, especially in mechanics, but the laws or quantitative relations are very numerous. Moreover, the comparisons made by the chemical student are for the most part qualitative in character; that is to say, they involve observation upon such things as the formation of precipitate, the evolution of a gas, a ready solubility or a change in color, and though the result may be more or less the particular amount is of no consequence. It is for this reason easy to arrange a laboratory course whose aim shall be to acquaint the student with such reactions, and we accordingly find him diligently employed in trying to find out what effect sulphuric acid will have on barium chloride or what silver nitrate has done to his fingers.