Heroes of Science: Chemists

by M. M. Pattison Muir

Chemistry was thus endowed with a grand and far-reaching conception, which has been developed and applied by successive generations of investigators: but we must not forget that it was the thorough, detailed work of Black and Lavoisier which made possible the great theory of Dalton.

At the time when Dalton was thinking out his theory of atoms, Davy was advancing as a conqueror through the rich domain which the discovery of Volta had opened to chemistry. Dalton, trained to rely on himself, surrounded from his youth by an atmosphere in which "sweetness and light" did not predominate, thrown on the world at an early age, and obliged to support himself by the drudgery of teaching when he would fain have been engaged in research, and at the same time—if we may judge from his life as recorded by his biographers—without the sustaining presence of such an ideal as could support the emotional part of his nature during this time of struggle,—Dalton, we found, withdrew in great part from contact with other scientific workers, and communing only with himself, developed a theory which, while it showed him to be one in the chain of thinkers that begins in Democritus and Leucippus, was nevertheless stamped with the undeniable marks of his own individuality and genius, and at the same time was untouched by any of the hopes or fears, and unaffected by any of the passions, of our common humanity.

Davy, on the other hand, was surrounded from childhood by scenes of great natural beauty and variety, by contact with which he was incited to eager desire for knowledge, while at the same time his emotions remained fresh and sensitive to outward impressions. Entering on the study of natural science when there was a pause in the march of discovery, but a pause presageful of fresh advances, he found outward circumstances singularly favourable to his success; seizing these favourable circumstances he made rapid advances. Like Lavoisier, he began his work by proving that there is no such thing in Nature as transmutation, in the alchemical meaning of the term; as Lavoisier had proved that water is not changed into earth, so did Davy prove that acid and alkali are not produced by the action of the electric current on pure water. We have shortly traced the development of the electro-chemical theory which Davy raised on the basis of experiment; we have seen how facts obliged him to doubt the accepted view of the composition of hydrochloric acid and chlorine, and how by the work he did on these subjects chemists have been finally convinced that an element is not a substance which cannot be, but a substance which has not been decomposed, and how from this work has also arisen the modern theory of acids, bases and salts.

We found that, by the labours of the great Swede J. J. Berzelius, the Daltonian theory was confirmed by a vast series of accurate analyses, and, in conjunction with a modification of the electro-chemical theory of Davy, was made the basis of a system of classification which endeavoured to include all chemical substances within its scope. The atom was the starting-point of the Berzelian system, but that chemist viewed the atom as a dual structure the parts of which held together by reason of their opposite electrical polarities. Berzelius, we saw, greatly improved the methods whereby atomic weights could be determined, and he recognized the importance of physical generalizations as aids in finding the atomic weights of chemical substances.

But Berzelius came to believe too implicitly in his own view of Nature's working; his theory became too imperious. Chemists found it easier to accept than to doubt an interpretation of facts which was in great part undeniably true, and which formed a central luminous conception, shedding light on the whole mass of details which, without it, seemed confused and without meaning.

If the dualistic stronghold was to be carried, the attack should be impetuous, and should be led by men, not only of valour, but also of discretion. We found that two champions appeared, and that, aided by others who were scarcely inferior soldiers to themselves, they made the attack, and made it with success.

But when the heat of the battle was over and the bitterness of the strife forgotten, it was found that, although many pinnacles of the dualistic castle had been shattered, the foundation and great part of the walls remained; and, strange to say, the men who led the attack were content that these should remain.

The atom could no longer be regarded as always composed of two parts, but must be looked on rather as one whole, the properties of which are defined by the properties and arrangements of all its parts; but the conception of the atom as a structure, and the assurance that something could be inferred regarding that structure from a knowledge of the reactions and general properties of the whole, remained when Dumas and Liebig had replaced the dualism of Berzelius by the unitary theory of modern chemistry; and these conceptions have remained to the present day, and are now ranked among the leading principles of chemical science; only we now speak of the "molecule" where Berzelius spoke of the "atom."

Along with these advances made by Dumas, Liebig and others in rendering more accurate the general conception of atomic structure, we found that the recognition of the existence of more than one order of small particles was daily gaining ground in the minds of chemists.

The distinction between what we now call atoms and molecules had been clearly stated by Avogadro in 1811; but the times were not ripe. The mental surroundings of the chemists of that age did not allow them fully to appreciate the work of Avogadro. The seed however was sown, and the harvest, although late, was plentiful.