CHEMICAL LABORATORIES. The appearance of the earliest chemical laboratories is familiar, since they formed attractive subjects for the con temporary artists. Not merely were these labo ratories used for experiment, but also for the teaching of pupils and assistants. At present, any well-lit room. supplied with water, gas, elec tricity, and a hood emnimmieating with a flue to carry off noxious gases, may serve for almost all chemical work. The water-supply operates and can he made to furnish air under pressure by means of a tromp; power can he obtained either from small or electric motors. and the gas furnishes heat. :NIneh chemi cal work, both scientific and technical, is carried out in such laboratories. originally built for other purposes. The most important chemical laboratories, however. arc 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 instruetors and advanced students and for the regular instruction of the mass of the stu dents. The wide extension of this class of ratories began with the famous laboratory erected by Liebig it Giessen in 1S'25. after which teach ingdahoratories, each showing an advanee on the preceding, sprang up at almost all the German universities and quickly reached a high degree of excellence.
The laboratory buildings arc 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 chemist/7 to which each is (Iv/heated vary with the size of the building and the importance assigned to different sub jects and to teaching and investigation respect ively. ,Nlany laboratories consist of a large lee ture-room, a large room for simple inorganic preparations and qualitative analysis; another large room for quantitative analysis and in organic research; a third large room for or ganic chemistry; and a number of small rooms to serve as class-room s. library. balance-rooms, private laboratories and offices for the instruc tors, for gas and water analysis, for physical chemistry, as furnace-room, combustion-room, hydrogen-sulphide room, storerooms, toilet-rooms, etc. In some eases separate buildings are pro vided for particular branches of chemistry. For example, the University of Gottingen has a sepa rate 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 consid eration 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 con siderations 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 elabo rately 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 he turned off every evening at the close of work. Water is carried, not merely to each room, hut commonly to each desk. Where the water is supplied under a strong pres sure. injector vacuum-pumps are used. but when this is not the ease, the whole building must be supplied with pipes connected with a vacuum steam-pump. In any case such a pinup, with connecting pipes to each desk, is almost a neces sity in the organic laboratory, for distilling un der reduced pressure. Another steam-pump sup plies a series of pipes. carrying air under pres sure. There are steam or hot-water pipes for heating and pipes for steam at high pressure for beating 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 dis tributed to several points by pipe, but the intro Cuction into eommerce of compressed oxygen in strong steel cylinders has made this system obso lete. Hydrogen-sulphide gas is also carried, in most cases, by pipes to several rooms. The sys tem of pipes for carrying off waste wafer must be earefully planned. Ordinary plumbing is de stroyed in a few years by acids and compounds of mercury. An excellent plan is to carry the waste water by open trough.; to the vertical earthenware main pipes, so avoiding leadwork altogether. The system of flues for ventilation of the hoods must be carried over the whole building. This system lint be eonnected with, a lofty chimney. or with a rotary fan. Electricity is usually supplied, for scientific purposes, front accumulator batteries.
Each student working in a room has a locked dusk for his own lase. The desks are usually supplied with gas, water. vacuum-pumps,draught closets, apparatus, and reagents, so as to reduce to a minimum the eases in whielt it is necessary for the student to leave his desk. Space is econ omized in most laboratories. in the set apart for beginners, by dividing the space under each desk into two independent closets, so that Iwo students may use the same desk at different hours or on different days. lit the larger labor atories much special apparatus is found, such as a machine for produeing liquid air, grinding mills driven by power, working models of chemi eal industrial works, and apparatus for treating materials on an industrial scale.
The technical laboratories maintained by in dustrial establishments may be simply for analytical work, in which ease they may be modeled after the rooms for quantitative analysis in the teaching laboratories; but in eases where experimental work is carried on. the plan is quite different. Power must he supplied more freely. facilities provided for handling larger quantities of material, and liberal space left free to set up working models of apparatus on a large scale. Sec section on Enginecriny Laboratories.