Page:The New International Encyclopædia 1st ed. v. 04.djvu/648

* CHEMISTRY. 56C would be denoted thermochemically in the follow- ing form: HClAq + KOHAq — KClAq -f 57.3J. In this manner the thermocliemical notation i;ives brief, complete, and precise expression to all the important facts connected with the trans- formations of matter. The number of kilojonlcs represents the total amount of energj' given off or taken up, whether all that energj' is in the form of heat, or part of it is in the form of mechanical work, light, or electricily. HISTORY. Ancient History. The history of ancient phi- losophy records certain theorics of matter, wliieh have had a directing influence on chemical thought during later centuries. The most im- portant ideas date from the Fifth Century n.c. Empedocles ( c.490-30 B.C. ), who may have de- rived his view-s from the ancient philosophers of the East, held that air, water, earth, and fire are four elements unrelated to one another and forming the basis of the universe. Aristotle (B.C. .384-22) added a fifth element, ousia {ovcia), a, purely spiritual substance pervad- ing the infinitj' of space. During the Middle Ages not a little energy was lost in researches after this 'fifth essence,' which, by confusion of ideas, came to be regarded as a fifth elementary form of matter. To Aristotle the material ele- ments were not altogether different from one an- other, but were forms of a primary substance differentiated by properties — as dry, moist, hot, cold — that were not essential to its nature. Hence, later, the alchemists' attempts to turn metals into one another, crowned by the belief that such transmutations cannot be effected by any knora means. The atomic conception dates from Democ- ritus ( c.4(iO-,'?70 n.r.). who held that all bodies are made up of the atoms of one and the same substance, and that the differences exhibited by the various forms of matter are due entirely to differences in the size and shape of their atoms. It is hardly necessary to st^ate that if this unde- veloped idea of Democritus had not furnished a suggestion that led to the building up of a useful chemical doctrine, it would deserve no mention in the history of science. It is thus clear that the ancients did nothing directly toward the building up of a science of chemistry. Indeed, how much chemical knowledge can we expect to find in an age when a man like Aris- totle did not hesitate to assert that a vessel will hold as mxich water if filled with ashes as when empty ? However, the ancients knew some facts and processes which lie within the scope of modern chemistry. Most of that knowledge was gained empirically by the Egyptians, and was by them communicated to the .Tews and Plioenicians, and later to the Greeks and Romans. The metallurgy of gold, silver, copper, iron, lead, tin, mercury, and perhaps zinc, and the preparation of cert^ain alloys, were known at quite an early date. The Egyptians had highly developed the art of mak- ing glass and of coloring it by means of certain metallic oxides, and many extant specimens of Egj'ptian pottery are beautifully enameled in various colors. The art of dyeing fabrics with the aid of mordants had likewise been developed at an early date, and many mineral and organic coloring matters were known to the Egyptians, Pha-nicians, and Jews. The Egyptians were also CHEMISTRY. l)robably the first to employ substances for medicinal purposes. Alchemy. Egypt was the birthplace of al- chemy, the pretended art of making gold and silver from base metals. Based on superficial ob- servation and the erroneous interpretation of phenomena, this pseudo-art subsequently ab- sorbed the attention of men for many centuries (see AxciiEMY), .and rendered scientific progress, and lience the development of the useful arts, impossible. Thus, the arts of metallurgy and of dyeing remained through the Middle Ages prac- tically what they had been in Egypt long before the beginning of our era. Neverl^heless. in their fantastic search after the philosopher's stone, the alchemists discovered methods of preparing many new substances, perfected many processes of manipulation, and thus slowly paved the way for the future investigator. Piisnuitli and anti- mony, sulpliuric. hydrocliloric. and nitric acids, the chloride and the carbonate of ammoniiun, the nitrates of potassium and silver, compounds of mercury, antimony, and arsenic — these and many other important substances were first pre- pared and their properties were first studied by the alchemists. Of course, the interpretation of known facts was absurd, based as it often was on the most grovindless assumptions — lor in- stance, the assuin])tion that most substances and certaiul}' all metals contain sulpliur. .s to the compounds of carbon, the alchemists did hardly anything toward laying a foundation for future organic chemistry, although tlicy learned to con- centr.ate aqueous acetic acid by distillation and to prejiare a few metallic acetates, and were familiar with certain reactions, such as the trausfornuilion of ordinary alcohol under the influence of sulpliuric acid, the formation of cer- tain esters, etc. A number of substances de- rived from the organic world were also used for medicinal purposes; but it was not until the lieginning of the 'iatrochemical' period that the art of preparing substances liegan to be looked upon as a handmaid of medicine. Alchemy prop- er had only one great object in view — to en- noble the base metals and to prolong life in- definitely — and this remained the principal aim of some of the best men even to the close of the era of iatrochcniistrii', and even the scientific achievements of more recent times have not suf- ficed to banish the fancy completely. Iatrochemlstry (Gk. iaTp6r, iatros, physi- cian). Tlic first great iatrocliemist was Para- celsus ( 1493-1. '541 ). who taught that the aim of chemistry was the preparation, not of gold, but of therapeutic agents. .'do])ting a view cur- rent among alchemists prior to his time, he held that, everything being composed of sulphur, mer- cury, and salt, if the amount of any of these happens to rise above or fall below the normal in the animal body, the result is a condition of disease. Hence, disease must be comliated by chemical means. Paracelsus therefore devoted himself to pharmacy and medical chemistry, and soon became famous through the many happy cures that he actually succeeded in effecting. Unfortunately the adventurous life that hv IimI. and his gross lack of modesty, aroused suspicion in man.v, and the bitterest opposition among the more conservative members of the medical pro- fession, and obscured his fame and greatly di- minished the sphere of his influence. Neverthe- less, his great work was accomplished; pure