apothecaries, alchemists, and astrologers of the Middle Ages, given over largely to the search for the philosopher's stone, and to the manufacture of elixirs, drugs, charms, cosmetics, etc. With the fifteenth century came the reaction against Scholasticism; and men began to study nature rather than books, they began to observe rather than to deduce facts and principles, and by the end of the sixteenth century the experimental method was well established.
In 1589 Galileo demonstrated the necessity of the experimental method at Pisa. Climbing the leaning tower, he let fall a weight of one pound and a weight of one hundred pounds; starting simultaneously, the weights struck the ground together, at once and forever disproving the Aristotelian deduction that the speed of falling bodies was proportional to their weights. Francis Bacon, in 1620, and Comenius, in 1630, set forth arguments for the inductive method and the experimental investigation of facts. But prior to the nineteenth century all laboratories were private institutions devoted wholly to research. In 1824 Purkinje established a physiological laboratory in Breslau; in 1825 Liebig established a laboratory of chemistry, medicine, and physiology in Giessen; in 1845 Lord Kelvin—then William Thomson—opened a physical laboratory in the University of Glasgow; in 1849 a pharmacological laboratory was created by Buchheim; in 1856 Virchow opened a pathological laboratory in Berlin. As the work of the laboratories has developed, there has come about a specialization of the problems to be undertaken, and as a result new research laboratories are founded every year.
Laboratories for instruction do not differ materially from research laboratories as far as equipment and method is concerned.
Chemical Laboratories. The appearance of the earliest chemical laboratories is familiar, since they formed attractive subjects for the contemporary artists. Not merely were these laboratories used for experiment, but also for the teaching of pupils and assistants. At present, any well-lit room, supplied with water, gas, electricity, and a hood communicating with a flue to carry off noxious gases, may serve for almost all chemical work. The water-supply operates vacuum-pumps, and can be made to furnish air under pressure by means of a tromp; power can be obtained either from small water or electric motors, and the gas furnishes heat. Much chemical work, both scientific and technical, is carried out in such laboratories, originally built for other purposes. The most important chemical laboratories, however, are buildings, constructed entirely for chemical work, in connection with the great universities and schools of science, and are intended both for investigation on the part of the instructors and advanced students and for the regular instruction of the mass of the students. The wide extension of this class of laboratories began with the famous laboratory erected by Liebig at Giessen in 1825, after which teaching-laboratories, each showing an advance on the preceding, sprang up at almost all the German universities and quickly reached a high degree of excellence.
The laboratory buildings are divided into rooms of varying sizes, each room assigned to one or more branches of chemical science, so that each student passes, during his course, through most of the rooms. In France a less systematic arrangement, avoiding large rooms, is preferred by some chemists. The number of the rooms and the branch of chemistry to which each is dedicated vary with the size of the building and the importance assigned to different subjects and to teaching and investigation respectively. Many laboratories consist of a large lecture-room, a large room for simple inorganic preparations and qualitative analysis; another large room for quantitative analysis and inorganic research; a third large room for organic chemistry; and a number of small rooms to serve as class-rooms, library, balance-rooms, private laboratories and offices for the instructors, for gas and water analysis, for physical chemistry, as furnace-room, combustion-room, hydrogen-sulphide room, storerooms, toilet-rooms, etc. In some cases separate buildings are provided for particular branches of chemistry. For example, the University of Göttingen has a separate building for physical chemistry.
In the larger laboratories almost every branch of chemistry has its separate room. Few general principles can be laid down for the plan of the building and the relation of the rooms to each other. The first consideration is to obtain abundant light. Everything should give way to this. Next the office and private laboratory of each professor should be central with reference to the rooms under his care. However, when permanent and responsible assistants are in immediate charge of the large rooms, this consideration is of less importance. Of course, such rooms as balance-rooms, combustion-rooms, and hydrogen-sulphide rooms, must be close to the large rooms to which they belong. Special considerations will decide the position of various rooms. Thus, a furnace-room is placed on the lowest floor to get the advantage of a high chimney. All chemical laboratories are elaborately piped. There is usually one system for gas used in heating, another for gas used in lighting, and often a third for certain specially protected gas-jets, which are required to burn continuously for long periods. This permits the rest of the gas to be turned off every evening at the close of work. Water is carried, not merely to each room, but commonly to each desk. Where the water is supplied under a strong pressure, injector vacuum-pumps are used, but when this is not the case, the whole building must be supplied with pipes connected with a vacuum steam-pump. In any case such a pump, with connecting pipes to each desk, is almost a necessity in the organic laboratory, for distilling under reduced pressure. Another steam-pump supplies a series of pipes, carrying air under pressure. There are steam or hot-water pipes for heating and pipes for steam at high pressure for heating stills, water-baths, and steam-closets. In addition, in some laboratories distilled water is distributed to the different rooms, by a system of block tin pipes. Formerly oxygen was distributed to several points by pipes, but the introduction into commerce of compressed oxygen in strong steel cylinders has made this system obsolete. Hydrogen-sulphide gas is also carried, in most cases, by pipes to several rooms. The system of pipes for carrying off waste water must be carefully planned. Ordinary plumbing is destroyed in a few years by acids and compounds of mercury. An excellent plan is to carry the
