fly into pieces, whether the flame is short or long, or more or less smoking, the liberation of odors, brittleness, etc.), chemical composition of the fuel, and of the pulverulent, sintered, or clinkered ash, etc.

77. EXAMINATION OF FURNACE GASES.

To be able to judge the processes taking place dur ing combustion,' the velocity of the flue gases, and the amount of air passing through the furnace are determined by an anemometer, the strength of the draught by a draught meter, the intensity of the heat by a pyrometer,* and the amount of carbonic acid, carbonic oxide, and free oxygen in the furnace gases are ascertained

1. By means of Orsat's apparatus.-With some experience and intelligence this apparatus gives results available for practical purposes, even in unscientific hands. It is based upon the principle, that a measured volume of gas is conducted through agents for the absorption of its principal constituents (caustic potassa for carbonic acid, potassium pyrogallate for oxygen, and solution of cuprous chloride for carbonic oxide), the volume of gas remaining after each absorption being measured, when the amount

1 Kerl, Thonwaarenindustrie, 1879, p. 301. Töpfer- u. Ziegler-Ztg. 1878, No. 1.

Dingler, clxxi. 43 (List). Notizbl. der deutsch. Ver. f. Fabrikation von Ziegeln u. s. w. ix. 96 ; xi. 191; xiii. 40, 42. Töpfer- u. Ziegler-Ztg. 1877, No. 46.

4 Kerl, Grundr. d. allg. Hüttenkunde, 1879, p. 85. Mitchell, Practical Assaying, p. 131.

5 Fichet-Ramdohr, Gasfeuerung, Halle, 1875. Ann. des mines, vol. viii. livr. 6 de 1875. B. u. h. Ztg. 1874, p. 232; 1875, p. 143; 1876, p. 72; 1877, p. 147. Dingler, ccxix. 420 (Weinhold). Fresenius' Ztschr. 1877, p. 343 (Seyberth). Oest. Ztschr. 1877, No. 11, 13, 16. Ztschr. de Ver. deutsch. Ing. xx. 318. Dingler, ccxxvii. 258; ccxxix. 262 (Fischer.) Winkler, Anleitung z. Chem. Untersuchung der Industriegase, 2 Abth., 1877, p. 1859.

of each will be ascertained from the difference. The арparatus is placed in a portable wooden case, and, according to Fischer's latest construction, is arranged as follows, (Fig. 63):

A is a burette inclosed in a glass cylinder. Its lower end is connected with the water flask E by means of a rubber tube. The burette is capable of holding 100 cubic

centimeters (6.1 cubic inches). Its lower part holding 40 cubic centimeters (2.44 cubic inches) is graduated to onefifth cubic centimeter (0.012 cubic inch), and the upper part in whole cubic centimeters (0.061 cubic inch). B CD are the absorption vessels (B for caustic potassa, C

for potassium pyrogallate, and D for solution of cuprous chloride, or a fluid obtained by shaking copper hammer scale with a mixture of equal volumes of ammonia and cold saturated solution of sal ammoniac). The vessels are filled with fine glass tubes and connected with the burette by means of a system of thick-walled capillary tubes. a b c are plain cocks; d is a Winkler cock (Fig. 64, B), which besides having a simple perforation is also cut lengthwise. The outer end, a, is connected with an aspirator by means of a rubber tube. When the cock is properly set, the tube e (which is provided with a little water, and loosely filled with cotton, in order to saturate the gas with water vapor and to retain dust), and the gas-conducting tube connected with it, can then be filled with the gas to be examined.

The operation is conducted as follows: The cock d is set so that it communicates with the outer air. The flask E, filled with water, is raised so that A will become completely filled with water, the air escaping from d. d is then closed towards A. The cock a is now opened and the flask E lowered, whereby the absorption vessel B is filled with the absorbing liquid (potassium hydrate) to the mark immediately below the cock a, whereupon this is closed. C is filled in a similar manner with potassium pyrogallate, and D with a solution of cuprous chloride from vessels of equal size communicating with and placed behind them. The furnace gas to be examined is aspirated through the aspirator, and the connection between e and A is established by the cock d, after the burette A has been completely filled by raising the flask E. The latter is then lowered, when A will be become filled with the gas. being properly set, the gas is allowed to escape by d again raising E, in order to expel any small quantities of air which may still be contained in the capillary tubes.

After A has in this manner been filled with gas, this is successively forced by the same manipulation through B, C, and D, and each time returned to A, in order to measure the volume of gas which has been absorbed respectively in B, C, and D.

Orsat has further enlarged his apparatus so that hydrogen and carburetted hydrogen can be also determined.1 An apparatus for examining gas, by Schwackhöfer, has recently been recommended, it being claimed that it is less easily broken and safer to handle than Orsat's.

2. By means of Bunte's burettes (Fig. 65).—An unlimited number of absorbing agents can be used in this apparatus, as it allows of the removal of the absorbing liquids from the burette without a loss of gas every time after they have been used, and further permits the gas inclosed in the burette to be brought, after each absorp tion, to the same pressure. A is a burette divided from the Winkler cock, a, to the common cock, b, into some what more than 110 cubic centimeters (6.71 cubic inches) and fractions. t is a funnel forming the upper part of the burette, having a capacity of 25 cubic centimeters (1.52 cubic inches) to the mark m. The burette, A, is filled with gas by connecting a with the gas-conductor by means of a rubber tube, and aspirating the gas through b until all the air has been expelled from A. a and b are then closed, and a rubber tube, plugged at one end with a small glass rod, is pushed over the point of a. In order to bring the volume of gas in the burette to 100 cubic centimeters (6.1 cubic inches) under a known pressure,

1 Ann. d. min. 1875, t. viii. p. 501. Oest. Ztschr. 1877, No. 13. B. u. h. Ztg. 1878, 123. Dingler, ccxxi. 284; ccxxvii. 171 (Fischer). Winkler, Anl. z. chem. Untersuchung der Industriegase, 2 Thl. p. 198.

2 Ztschr. der berg- u. hüttenm. Ver. für Steyermark u. Kärnthen, 1878, No. 3-6, p. 78.

3 Dingler, ccxxvii. 167; ccxxviii. 46.

water is forced into the burette up to the 0 point by means of a rubber hose filled completely with water, and connected with the funnel, T, and the point of the burette. b is then closed, and a opened towards m, whereby a part of the gas escapes, and the inclosed remaining part stands under the pressure of the atmosphere and a column of water a few cubic centimeters high. The gas can in a similar manner be brought under equal conditions of pressure at any desired position of the liquid in the burette, and a correction for the pressure, which is made the same at every reading, is not required in the customary statement of the results of the experiments in per cents. of the total volume.

The following is the process of manipulating when furnace gases in the burette contain carbonic acid, carbonic oxide, and oxygen. The minutely perforated point, b, of the burette is connected with the flask, F, by the rubber tube r. The cock b is then opened and air drawn through the tube s by

out

T

Fig. 65.

m

100

90

suction, whereby water is

drawn from the burette A to F, and then b is immediately closed. The flask, F, is removed from the burette,

and the point of this is dipped solution of potassium hydrate.

into a dish containing

When the cock b is