Heroes of Science: Chemists

by M. M. Pattison Muir

We saw that Dumas accepted, with some hesitation, the distinction drawn by Avogadro, but that failing to carry it to its legitimate conclusion, he did not reap the full benefit of his acceptance of the principle that the smallest particle of a substance which takes part in a physical change divides into smaller particles in those changes which we call chemical.

To Gerhardt and Laurent we owe the full recognition, and acceptance as the foundation of chemical classification, of the atom as a particle of matter distinct from the molecule; they first distinctly placed the law of Avogadro—"Equal volumes of gases contain equal numbers of molecules"—in its true position as a law, which, resting on physical evidence and dynamical reasoning, is to be accepted by the chemist as the basis of his atomic theory. To the same chemists we are indebted for the formal introduction into chemical science of the conception of types, which, as we found, was developed by Frankland, Kekulé, and others, into the modern doctrine of equivalency of groups of elementary atoms.

We saw that, in the use which he made of the laws of Mitscherlich, and of Dulong and Petit, Berzelius recognized the importance of the aid given by physical methods towards solving the atomic problems of chemistry; but among those who have most thoroughly availed themselves of such aids Graham must always hold a foremost place.

Graham devoted the energies of his life to tracking the movements of atoms and molecules. He proved that gases pass through walls of solid materials, as they pass through spaces already occupied by other gases; and by measuring the rapidities of these movements he showed how it was possible to determine the rate of motion of a particle of gas so minute that a group of a hundred millions of them would be invisible to the unassisted vision. Graham followed the molecules as in their journeyings they came into contact with animal and vegetable membranes; he found that these membranes presented an insuperable barrier to the passage of some molecules, while others passed easily through. He thus arrived at a division of matter into colloidal and crystalloidal. He showed what important applications of this division might be made in practical chemistry, he discussed some of the bearings of this division on the general theory of the molecular constitution of matter, and thus he opened the way which leads into a new territory rich in promise to him who is able to follow the footsteps of its discoverer.

Other investigators have followed on the general lines laid down by Graham; connections, more or less precise, have been established between chemical and physical properties of various groups of compounds. It has been shown that the boiling points, melting points, expansibilities by heat, amounts of heat evolved during combustion, in some cases tinctorial powers of dye-stuffs, and other physical constants of groups of compounds, vary with variations in the nature, number and arrangements of the atoms in the molecules of these compounds.

But although much good work has been done in this direction, our ignorance far exceeds our knowledge regarding the phenomena which lie on the borderlands between chemistry and physics. It is probably here that chemists look most for fresh discoveries of importance.

As each branch of natural science becomes more subdivided, and as the quantity of facts to be stored in the mind becomes daily more crushing, the student finds an ever-increasing difficulty in passing beyond the range of his own subject, and in gaining a broad view of the relative importance of the facts and the theories which to him appear so essential.

In the days when the foundation of chemistry was laid by Black, Priestley, Lavoisier and Dalton, and when the walls began to be raised by Berzelius and Davy, it was possible for one man to hold in his mental grasp the whole range of subjects which he studied. Even when Liebig and Dumas built the fabric of organic chemistry the mass of facts to be considered was not so overpowering as it is now. But we have in great measure ourselves to blame; we have of late years too much fulfilled Liebig's words, when he said, that for rearing the structure of organic chemistry masters were no longer required—workmen would suffice.

And I think we have sometimes fallen into another error also. Most of the builders of our science—notably Lavoisier and Davy, Liebig and Dumas—were men of wide general culture. Chemistry was for them a branch of natural science; of late years it has too much tended to degenerate into a handicraft. These men had lofty aims; they recognized—Davy perhaps more than any—the nobility of their calling. The laboratory was to them not merely a place where curious mixtures were made and strange substances obtained, or where elegant apparatus was exhibited and carefully prepared specimens were treasured; it was rather the entrance into the temple of Nature, the place where day by day they sought for truth, where, amid much that was unpleasant and much that was necessary mechanical detail, glimpses were sometimes given them of the order, harmony and law which reign throughout the material universe. It was a place where, stopping in the work which to the outsider appeared so dull and even so trivial, they sometimes, listening with attentive ear, might catch the boom of the "mighty waters rolling evermore," and so might return refreshed to work again.

Chemistry was more poetical, more imaginative then than now; but without imagination no great work has been accomplished in science.