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Page:Popular Science Monthly Volume 35.djvu/832

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THE POPULAR SCIENCE MONTHLY.

taken for other purposes; the knowledge of the making of china and of the separation of phosphorus resulted from experiments intended for producing gold. But the principal successes of modern science in general, and of chemistry in particular, were obtained in a speculative, inductive way, the only one to be considered as actually scientific. With positive surety the astronomer, from the movements of the stars, and from the attracting forces which they thereby manifest, can ascertain the presence of another star which has never been observed before. He may prophesy a solar eclipse to the accuracy of a minute, and many years before predict the return of a comet. In a similar way exact chemical knowledge often enables us to foretell the formation of certain compounds hitherto unknown, and to define the properties they may be expected to have. It was in this way that, the composition and chemical structure or arrangement of atoms in the molecule of conine and conhydrine having been explored, their preparation was likewise effected, the operators being guided by logical inferences. This scientific way of proceeding proved successful in numerous cases, and led to some surprising results in the course of the last year.

Not many years ago what was known regarding the source from which common plants draw their food consisted in the recognized fact that carbonic acid and water, both abundant in air and fertile soil, are taken up by the roots, converted into sugar by an unknown process, the sugar afterward being transformed into cellulose, the matter chiefly constituting the body of the plant, and into starch. It was also known that oxygen was set free in the course of these changes. In 1870 Baeyer promulgated a theory, explaining how assimilation of the mentioned substances might be effected. He demonstrated the possibility of "formaldehyde" being produced from carbonic acid and water, which is only possible, if—as is the case—oxygen is liberated. All plants in daylight exhale oxygen and absorb carbonic acid. Formaldehyde, a gaseous compound, is, as aldehydes in general are, very liable to condense to solid compounds by accumulating a greater number of atoms into one molecule. Baeyer expressed his belief that sugar, the composition of which agrees with that of formaldehyde multiplied by six, is the product of such a condensation.[1]

The first signs that sugar might result from such a condensation, when conducted in the proper way, were observed by Butlerow, but since he claimed to have prepared a sugar-like compound from formaldehyde, all the experiments undertaken to the

  1. The chemical changes in question are represented by the equations:

    Carbonic acid and water = formaldehyde and oxygen
    CO2+H2O=CH2O+O2
    Six formaldehydes, 6CH2O = C6H12O6, grape-sugar.