In order to prove this novel conclusion he started afresh from the Cartesian " I think " in the Kantian form of the synthetic unity of apperception acting by a priori categories; but instead of allowing, with all previous metaphysicians, that the Ego passively receives sensations from something different, and not contenting himself with Kant's view that the Ego, by synthetically combining the matter of sensations with a priori forms, partially constructs objects, and therefore Nature as we know it, he boldly asserted that the Ego, in its synthetic unity, entirely constructs things; that its act of spontaneity is not mere synthesis of passive sensations, but construction of sensations into an object within itself; and that therefore understanding makes as well as shapes Nature.
There are many substances produced by plants which can be synthetically prepared by chemical means, but, as with quinine, the process involved is too costly to enable the synthetic product to compete with the natural product.
Fischer's a-acrose therefore led to the synthesis of the dextro and laevo forms Gf mannose, glucose and fructose; and these substances have been connected synthetically with many other sugars by means of his cyanhydrin process, leading to higher sugars, and Wohl and.
Alcohol is produced by fermentation from vegetable substances containing starch or sugar, from fermentable sugars produced by the hydrolysis of cellulosic bodies, and synthetically from calcium carbide and from the ethylene contained in coal and coke-oven gases.
Liebermann in 1868 prepared that substance synthetically from anthracene, but their process was not practicable on a large scale, and it was left to him to patent a method that was commercially valuable.