Page:Popular Science Monthly Volume 29.djvu/545

Rh H. B. Baker communicated to the London Chemical Society results of his experiments on the influence of moisture in the combustion of carbon and of phosphorus in oxygen, his conclusions being that the combustion of dry charcoal in dry oxygen is incomplete and slower than in ordinary moist oxygen. In the discussion which followed Mr. Baker's paper, Dr. Armstrong pointed out the importance of these new facts in defining more accurately conceptions of chemical action, and suggested that chemical action is "reversed electrolysis." In his address as President of the Chemical Section of the British Association for the Advancement of Science (September 10, 1885), Dr. Armstrong further discussed this subject, and stated that the idea conveyed by the expression "reversed electrolysis" is found in the writings of Faraday, neglect of whose teachings retards the progress of chemistry.

Liquefied ammonia at -65° does not combine with sulphuric acid, but swims on its surface without mixing with it. Donny and Mareska long ago showed that sodium retains its luster in liquid chlorine at -80°, and quite recently Professor Dewar demonstrated that liquid oxygen is without action on sodium, potassium, phosphorus, solid sulphuretted hydrogen, and solid hydriodic acid. He further experimented with other substances normally active, and found their affinity at very low temperatures destroyed.

The speed of chemical reactions is an important factor in chemical theory, the study of which has but recently begun. Wenzel long ago held that the affinity of metals for a common solvent, such as nitric acid, was inversely as the time necessary to dissolve them, and he experimented with small cylinders partly protected by wax. Gladstone and Tribe have made attempts to ascertain the rate at which a metallic plate precipitates another metal from a solution, and they announced a definite law. Professor John W. Langley has since shown that, while their experimental work was correct, their method was faulty, and the results fallacious; he thinks it probable that the true law of chemical action where one metal precipitates another should be thus stated: The time during which one atom replaces another in a compound molecule is constant, and the total rate of chemical action varies directly as the mass of the reacting body in solution.

In his address before the Chemical Section of the American Association for the Advancement of Science, at Philadelphia, Professor Langley discussed the problems of chemical dynamics, and pointed out the rich store of promise in this neglected field. Physics deals with three quantities space, mass, and time. Chemistry has too long been content with studying the changes of matter in terms of space and mass only—that is to say, in units of atomic weight and atomic volume. The discovery of a time-rate for the attractions due to affinity is destined to throw new light on chemical science, and to render it capable of mathematical treatment.

A prodigious amount of work has been done in thermo-chemistry,