LOUIS PASTEUR.
LOUIS PASTEUR.
All the decompositions of organic matter, such as the decay of meats and vegetables, are now known to be forms of fermentation, due to the action of certain organisms known by the group name of bacteria. This discovery led naturally to the process of preserving organic compounds by sterilization. The principles on which this process depends are very simple. If an organic body, such as a fruit or vegetable, be subjected for some time to a high temperature,—that of boiling water will usually suffice,—the fermentation germs which it contains will be destroyed. If then it be sealed in such a way, either hermetically or with a plug of sterilized cotton, so that no living germ can reach it, decomposition cannot take place. Certain chemicals, such for instance as salicylic acid and formaldehyde, have the property of paralyzing or suspending germ action, and hence organic bodies treated with these substances may also be protected against decomposition.
The activity of fermentation is made use of in the technical arts. Bread is made light by fermentation, and wine, beer, and cider are made by the fermentation of fruits and grains. Alcohol is produced by the fermentation of grains and potatoes, their starch having previously been converted into sugar by malt.
Buchner has lately shown that all fermentation is of one kind, namely, that due to ferments of the diastase type. The fermentation produced by yeast, for instance, is not due, according to his observations, to the living cells, but to the products of their activity. By destroying yeast cells, by grinding and high pressure, and using their contents, he has secured a vigorous fermentation similar in every respect to that caused by the cells themselves.
The electric furnace, which affords a higher heat than chemists had been able to secure, has been the promoter of great advances in inorganic chemistry. Moissan (b. 1852), a French chemist, has been the most successful in applying the heat of the electric furnace to analytic and synthetic studies. One of the practical results which has come from these studies has been the virtual bridging over of the chasm which has been supposed to exist between organic and inorganic compounds. Under the influence of the heat of the electric furnace, carbon, which is the keystone of organic compounds,has been made to combine directly with the metals, forming a series of bodies known as metallic carbides. The carbide of calcium, under the action of water, yields a gas known as acetylene, which by a series of reactions can be converted into alcohol. Thus alcohol, which only a short time ago was supposed to be solely the product of organic life, is shown also to result from a simple inorganic reaction such as has been shown above.
The importance of electrolysis in metallurgical and analytical chemistry has already been noticed. So rapid has been the progress along these lines that the terms metallurgical chemistry and electro-chemistry are in some respects almost synonymous.
Electricity has also been employed in many of the chemical arts;e. g., in the promotion of crystallization and purification of organic solutions as practiced in the sugar industry.
DRIVING A NAIL WITH A HAMMER MADE OF FROZEN MERCURY.
DRIVING A NAIL WITH A HAMMER MADE OF FROZEN MERCURY.
Though belonging rather to analytical than to electro-chemistry, one may here mention the wonders of that discovery which belongs to the close of the nineteenth century, and which is known as “liquid air.” Until 1877 air—oxygen and nitrogen—was regarded as a permanent gas. Oxygen liquefies at 300° below zero and nitrogen at 320°. When air is cooled to those degrees it assumes a misty form and falls like raindrops to the bottom of the vessel. It then gives off vapor, like boiling water. If poured out on a conductor, as iron or ice, it assumes the gaseous state so rapidly as to amount to an explosion. The many experiments with it are simply wonderful, and the practical claims for it are without end. Already it runs an engine and motor vehicles. It is claimed that it will complete the problem of aerial navigation; that it is the coming power in gunnery and blasting; that it affords the ideal sanitation; that in surgery it offers the most perfect chemical cauterization.
There is no branch of science that holds such an intimate relation to the progress and welfare of man as chemistry. First of all, it is chiefly instrumental in providing him with food and clothing, as has been shown in the paragraph on agricultural chemistry. In the second place it has extended his domain over matter and, in connection with physics, has established the identity of the composition of the universe with that of the earth. The universe has thus been shown to be of a single origin and of uniform properties. By understanding the constitution of matter, with which he is surrounded, man is able to utilize to the best advantage the material at his disposal. Thus invention is promoted and the application of chemical knowledge in the arts extended.