water only, while the first pipette P' in which carbon dioxide is absorbed contains sodium hydrate dissolved in three times its weight of water. The second pipette P" in which oxygen is absorbed contains Pyrogallic acid dissolved in sodium hydrate in the proportion of five grams of the acid to 100 cc. of the hydrate, and in the third pipette wherein carbon monoxide is absorbed cuprous chloride is contained. These chemicals are sold by most of the large dealers.

Another series of formulas which work equally well and in many cases are more easily prepared, are the following:

To absorb the carbon dioxide, potassium hydroxide is used, and is made by diluting 500 grams of commercial potassium hydroxide in one quart of water. To absorb the oxygen, potassium-Pyrogallite is used wherein five grams of solid acid in 100 cc. of potassium hydroxide above mentioned is prepared. When over 28 per cent. of oxygen is present, it is necessary to use 12 grams of commercial potassium hydroxide to 100 cc. of water. To absorb the carbon monoxide, cuprous chloride is used which is prepared by covering the bottom of a quart measure with cuprous chloride (CuO) to a depth of 3gths of an inch. The measure is then filled with hydrochloric acid, shaken and allowed to stand until it becomes colorless. The copper wire is then placed in the solution and left to stand for a number of hours.

The Hemphel Apparatus for Determining the Hydrogen Content. It is seen from the above description that no means are provided to ascertain whether or not the hydrogen content of the fuel is being properly consumed. This determination can only be made by the refined laboratory apparatus of the chemist. The authors consider that such a test is beyond the scope of this work, hence the description of the Hemphel apparatus and its operation will not be undertaken in these pages. Standard works on this subject are, however, available in all chemical engineering libraries for those who desire to go into this subject. Except for refined tests covering certain particular problems in combustion the Orsat analysis of flue gases is considered sufficiently accurate for power plant practice. Indeed, in most instances, as we shall see, the determination of the carbon dioxide component alone gives us sufficient information for ordinary operating conditions.

Gas Analysis in the Power Plant.-The simple Orsat apparatus is used very extensively in many power plants. It is reliable and

accurate and its only objections are that it is a somewhat delicate instrument and requires careful manipulation.

There are on the market other instruments that are more rugged in construction and therefore more suitable for power plant work, by which it is possible to determine the CO2 only. While for any scientific investigation or accurate test it is necessary to determine the oxygen and CO as well as the CO2, there are many cases in practical operation where a determination of the CO2 alone is very valuable. Therefore, the simple instrument by which this can be done has a useful place in power plant work.

DRAIN

GAS

CHAMBER

MINERAL OIL

CONCENTRATED

CAUSTIC POTASH SOLUTION

One of these instruments which is illustrated in Fig. 173 is known as the Dwight CO2 Indicator. This instrument consists of a metallic vessel, into which is pumped a charge of the flue gas to be analyzed. The vessel contains a small quantity of Caustic Potash solution for the purpose of absorbing the CO2 in the sample. As soon as the gas is taken into the receiver the cocks are closed, and the instrument is shaken. to thoroughly mix the gas with the absorbent solution, thus removing Dwight Mfg. Co., Chicago, Pat. the CO2 content. A small amount of mineral oil floats on top of the Caustic Solution to keep the gas from coming in contact with the caustic until after the cocks are closed and the instrument shaken. Removing the CO2 in the gas reduces either its volume or its pressure. In this case, the volume remains constant, and consequently the removal of the CO2 reduces the pressure, in accordance with Boyle's Law (page 44). The reduction in pressure is measured by a small vacuum gauge, which is calibrated to read direct in percentage of CO2.

FIG. 173.- CO2 indicator.

applied for.

Another instrument known as the Pocket CO2 Indicator is illustrated in Fig. 174. This is a compact portable instrument that operates on the same principle as the Orsat, and makes accurate CO2 determinations.

Conclusion on the Orsat Analysis. By care and a little patience, the experimenter will find that the Orsat analysis as

above set forth can be taken easily and quite accurately, and thus a splendid lot of data obtained wherewith steam boiler economy and operation can be checked. If wrong conditions of combustion are found to prevail the proper adjustments can then be made in the furnace and its accessories.

We shall next proceed to formulate some equations whereby the data gained from the flue gas analysis may be thrown into more useful analytical form.

FIG. 174.-Pocket CO2 indicator (patented) made by Bacharach Industrial Instrument Co., Pittsburg, Pa.

CHAPTER XXXII

ANALYSIS BY WEIGHT, AND AIR THEORETICALLY REQUIRED IN FUEL OIL FURNACE

In the last discussion it was found that Orsat analyses of chimney gases are always made volumetrically. In computing combustion data from these analyses, however, it is often necessary to have the proportions or percentages by weight instead

FIG. 175.-Carbon dioxide recording machine located in the Long Beach Plant of the Southern California Edison Company.

of by volume. The volumes of carbon dioxide, oxygen, carbon monoxide, and nitrogen which constitute the chimney gas analysis of a sample volume by means of the Orsat apparatus will be represented by V1, V2, V3, V4, respectively in this discussion.

Let us now see how we may transfer this relationship so that proportions by weight of M1, M2, M3 and M4 pounds may respectively set forth the constituents of a flue gas sample of weight M pounds. Since we are only in search of proportions by weight-that is a ratio of M1 to M, M2 to M etc., it is evidently not necessary to actually know the quantitative values of the weights involved.

1

FIG. 176.-Recording thermometer and draft gage on Stirling boilers. Pacific Gas and Electric Company, station C, Oakland, Cal.

Fundamental Laws Involved. In a previous discussion we found (see page 48) that all perfect gases follow the composite law-namely, that at any particular state the product of its pressure p and volume V is equal to the product of its weight M and absolute temperature T multiplied by a constant R, or mathematically expressed