able importance; and it is not the absolute cost but the probable profit that most deserves consideration. A primary characteristic of perfumes is their immense strength; a very minute quantity of one is sufficient to produce a large effect. Consequently, they may bear a large price without limiting consumption. But, to isolate this as yet unknown perfume, it was necessary to treat enormous quantities of iris powder, and this required industrial resources which the inventors could not command. These were secured by making suitable arrangements with two large houses which became parties in interest. The experiments lasted ten years. First, irone, the principle to which the odor of the violet is due, was isolated. A complete chemical study of it was made. Having remarked that citral, an aldehyde abundantly diffused in Nature, gave, on condensation with acetone, an acetone of the same crude formula as irone, these authors effected this condensation under the influence of hydrate of baryta. They thus obtained, as they had expected, an acetone of the same crude formula as irone—false irone; this, it is true, had neither the odor nor the properties of irone, but by the action of dilute sulphuric acid it was transformed into its cyclic isomer, ionone. From the chemical point of view, ionone not being identical with irone, but only an isomer, the problem could not be said to be solved; but it was fully solved from the industrial point of view. Ionone possesses, like irone, the perfume of the violet, with a slight shade perceptible to practiced noses, but lending itself admirably to all the uses of perfumery. We have in this a complete example of methodical synthesis, although it must be admitted that the authors were aided by happy combinations of circumstances that might not always occur.
There are also chance syntheses. Thus, a substance, the odor of which may be utilized, is sometimes fallen upon in pursuing researches undertaken for another purpose. This is what happened, for example, in the case of Baur's artificial musk. M. Baur had undertaken the study of two carbides of hydrogen—two butyltoluenes contained in the essence of resin. He isolated and separated these substances, and then in experiments connected with the performance of the synthesis he perceived an extremely pronounced odor of musk appertaining to the trinitrile derivative of isobutyltoluene. M. Baur was not led to his researches by chance, but the discovery of his musk, the most precious result of them, was not anticipated by him.
There are other cases in which a series of bodies are prepared with full expectation of what the chemical results will be, but without knowing what odor they will have, or whether they will be odoriferous, but with the expectation that they will be, and
