SYNTHESIS (Gr. synth'isis, making a wt ole out of parts) is a term employed in chem istry to designate the building up of a more or less complicated product from its ele mentary constituents. As the synthesis of inorganic compounds is usually very simple, we shall confine our remarks to organic compounds. To take a very common substance as an illustration, there is no difficulty in resolving sugar into its ultimate elements, or, in other words, in ascertaining its composition by analysis. If we heat a little sugar to redness in a glass tube, it leaves a black deposit, which is carbon, while a liquid, which is water, distils over; and, on electrolyzing this liquid, we resolve it into hydrogen and oxygen; so that we can thus show that sugar is composed of the ultimate elements, carbon, hydrogen, and oxygen. An analysis of this kind shows that sugar may be rep resented by the formula C,21:11,01,, and that one atom, or any given weight of it, con tains 72 atoms or parts by weight of carbon, 11 of hydrogen, and 88 of oxygen. This pulling to pieces of the sugar is an easy matter, and has been known to chemists for more than half a century; but the putting together of the pieces, or, in other words, the synthesis of sugar, is a very much more difficult task. We may bring together carbon, hydrogen, and oxygen in the due proportions, and, to use the words of prof. Wanklyn (in a lecture delivered at the Royal institution, Feb. 12, 1864), "we may shake them all together, or heat them, or cool them, and yet we shall never get them to cogibine so as to form sugar. Alcohol consists of 24 parts of carbon, 6 parts of hydrogen, and 16 parts of oxygen; but no alcohol ever results from making such a mixture. Neither sugar nor alcohol can exist at the temperature to which it is requisite to raise our mixture of car bon, hydrogen, and oxygen, in order to get chemical action to set in. At ordinary temperatures, the organic elements will not enter into combination, while at high temperatures they combine, it is true, but yield comparatively very few compounds." There was a general belief that organic products, such as sugar, alcohol, urea, oxalic acid, taurine, leucine, etc., required for their production a mysterious so-called vital farce, totally distinct from the ordinary forces acting on matter. The first blow to this now obsolete doctrine was struck by WOhler in 1828, when he discovered that the organic base urea might be artificially obtained. See OnGAxrc COMPOUNDS. Three years after ward Pelouze obtained formic acid from inorganic materials. In 1845 Kolbe, by a somewhat complicated process, effected the synthesis of acetic acid, and consequently, indirectly, of its derivatives, among which may be enumerated acetone, the product of the destructive distillation of acetates; marsh gas, obtained by distilling an acetate with a caustic alkali, and ethylene; and the electrolysis of acetic acid, which Kolbe accom plished a few years afterward, yielded methyl and oxide of methyl, which latter could be transformed into any other methylic compound. During the last twelve years new
and simpler methods have been suggested by various chemists, among whom Berthelot must be especially mentioned, and enormous additions have been made to the list of so called organic compounds which have been synthetically constructed. We shall give a description of the mode of producing alcohol synthetically, and shall then show that from it, as a starting-point, an immense number of other organic compounds can be syn thetically produced. To obtain this product synthetically, several distinct steps are necessary. The first is the formation of a transparent colorless gas, acetylene, C4I1,, from carbon and hydrogen in the electric arc; by passing this gas through sub-chloride of copper, acetylide of copper is produced, which, in contact with nascent hydrogen, gives olefiant gas, C41=14; agitated with sulphuric acid, olefiant as produces sulphovinic acid, (a discovery due to our own chemists, Faraday and Hennell, in 1820). On distilling this acid diluted with water, dilute alcohol comes over, which, on redistillation, in contact with quick-lime, yields pure rinic or ordinary alcohol, having thus obtained ordinary alcohol from inorganic materials only, we may employ it to form by synthesis au immense number of other organic compounds. By means of what is known as " the process of Mendips," we can, as it were, step from one alcohol to the next above it. Thus, from vinic alcohol we obtain propylic (or tritylic) alcohol from this we obtain buty/ic (or tetrylic) alcohol from this, amylic alcohol and so on. From the propylic alcohol thus obtained we get, by oxidation, propionic acid, from which .lactic acid, the acid of sour milk, may be obtained; similarly, butylic alcohol yields butyric acid; every alcohol, in short, yielding a corresponding fatty acid by oxid'ation. Glycerine, the base of the fats, may also be obtained by a somewhat circuitous process. By combining glycerine with propionic acid, and with the other fatty acids may be synthetically formed, we obtain several oils and fats similar to those which occur as natural products. The case of tau rine, is even more striking; it is a product of various glandular metamor phoses, but its chief source is the bile, where it exists iu conjugation with cholic acid as tauro-cholic acid. This highly complex substance can readily be formed in the labora tory from sulphuric acid, alcohol, and ammonia, each of which is capable of being built up from its constituent elements.