In Fig. 51 is shown the

FIG. 52.

serviceable for all smaller operations. Acme Burner, patented in 1891 by T. Boyce, of New York; this is probably the most satisfactory burner made for small operations at the dispensing counter, and can be used for coal or gasoline gas. Each burner is provided with two tubes, one of the regular Bunsen pattern, the other with a gauze safety-tip (Fig. 52), permitting the flame to be turned down as low as desired, and out without receding. The supply of gas is regulated by turning the tube at A until the desired quantity of flame is obtained; by turning the milled disk, B, up or down, it being threaded and moving upon the nipple, the air-supply is adjusted. The height of the burner is 5 inches, including the base. The Finkner burner (Fig. 53) yields a very satisfactory flame, but is not adapted for very strong heat; it is so constructed that the supply of gas and admixture of air can be simultaneously regulated by turning the milled head. Fig. 54 represents a convenient adjustable burner; by turning the screw, which is accessible to the fingers while the burner is in use, the gas orifice can be so adjusted that any desired flame may be had. The air-supply is adjusted by turning the air-regulator up or down, it being threaded and moving upon the burner tube. The moving of the point up through the gas orifice, while reducing the gas quantity and size of the flame, does not reduce the gas pressure; the gauze safety-tip

Gauze tip and tube for the Acme burner.

(Fig. 52) can also be attached to this burner when a very small flame is desired. For maintaining low temperatures, as in the

testing of pepsin and similar operations, the double minim burner (Fig. 55) will be found useful.

For use with inflammable liquids the apparatus illustrated in Fig. 56 will be found serviceable, the burner being surrounded with safety

Double minim burner.

gauze, which prevents the flame from communicating with the vapor on the outside, the principle being the same as in the Davy safety lamps.

Fletcher's radial burner (Fig. 57) possesses some advantages over other heaters, in containing no loose parts and in being made entirely of annealed cast-iron; it is practically indestructible; if choked with dirt it is readily cleaned with a card or spatula.

The flames are practically solid safety burner, to be used for heating infiamwhen in use, and show no ten

mable liquids.

dency to run to a point in the centre; the consumption of gas amounts to from 12 to 18 feet per hour, and the burner will accommodate vessels from 10 to 18 inches in diameter.

FIG. 58.

For larger operations the "Jewel" gas-stove, Fig. 58, manufactured by Geo. M. Clark & Co., Chicago, will be found very serviceable. The cast-iron frame is twelve inches square and five inches high, thus standing very firm and capable of supporting large vessels. The gas is properly mixed with air before it enters the radial burner, where perfect combustion is effected, as shown by the pale-blue flame, which can be turned down very low without flickering. It consumes about eight feet of gas per hour, and is a most efficient heater. For regulating the degree of heat within certain narrow limits, special appliances have been devised, known as thermostats, by means

Jewel gas stove.

FIG. 59.

FIG. 60.

Reichert's thermostat.

The Bunsen Kemp gas regulator or thermostat.

of which the supply of gas admitted to the burner is automatically controlled by expansion and contraction of mercury contained in glass cups or tubes kept in contact with the air or liquid the temperature of which it is desired to maintain at, or near, certain points. All gas supplied to the burner is made to pass through the thermostat, and the required temperature having been reached, the gauge is set by means of a screw, after which the supply of gas is controlled by the expansion of the mercury caused by an increase of heat. Figs. 59 and 60 show two thermostats frequently employed.

The steam boiler, Fig. 61, designed by Prof. E. L. Patch, is a

most convenient source of heat for the requirements of a small laboratory. The boiler, 22 inches high and 10 inches in diameter, is made of steel, contains 20 flues, and is covered with a thick layer of asbestos composition, to prevent loss of heat by radiation; it has a capacity of 7 gallons and possesses one great advantage-that it can be heated by means of either a gas or a coal-oil stove. Being provided with a water-gauge, safety-valve and manometer, the boiler is as complete as any of larger size, and steam can be carried from it to any point desired; it is usually filled from above at the safety-valve, but, wherever water service is available, an injector may be attached, so as to allow of filling while steam pres

sure is on. The coil of pipe in the conically shaped metal case on the side, may be used for hot filtration, evaporation or drying pur

poses.

It is well known that steam, when coufined, is capable of absorbing large quantities of heat, and its temperature rises proportionally to the pressure exerted upon it; dense aqueous solutions, therefore, can readily be boiled by means of superheated steam.

For the proper control and distribution of heat, different devices are employed. When direct flame is to be applied to porcelain or glass vessels the interposition of wire-gauze or asbestos cloth will be found very desirable; for not only will the heat be supplied to a greater extent of surface by radiation, but at the same time it will

FIG. 62.

FIG. 63.

Sand-bath, shallow form.

Sand-bath, deep form.

be uniformly distributed, and thus insure more regular heating, which of itself is very important, considering the frail character of flasks and dishes.

The sand-bath is employed for temperatures above that of boiling water, and is chiefly intended to maintain a continuous supply of high

FIG. 64.

Large sand-bath, heated by steam.

heat and to prevent sudden depression of temperature from foreign causes; it is invaluable in the distillation of certain liquids (acids, etc.) from glass vessels, and may be either of deep or shallow form. (See