10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



oxide. To analyze such a gaseous mixture by the Orsat method 

 means simply to bring about the absorption of each one of the con- 

 stituents and determine by the resultant changes in volume the per- 

 centage composition. A solution of caustic potash will absorb carbon 

 dioxide but neither oxygen nor carbon monoxide ; further, a solution 

 of pyrogaUic acid and caustic potash will absorb oxygen ; and lastly, 

 an ammoniacal solution of cuprous chloride will absorb carbon 

 monoxide. These are the reagents used. Figure 2 shows a simple 

 form of Orsat apparatus. The graduated bulb on the right measures 

 a unit quantity of the flue gas to be analyzed ; the three bulbs to the 

 left contain the several absorption reagents ; that one immediately 

 adjoining the graduated bulb absorbs carbon dioxide ; the next to the 

 left absorbs oxygen ; and the last absorbs carbon monoxide. In 

 operation a measured quantity of flue gas is admitted into the gradu- 

 ated bulb, and by means of simple valves and the leveling bottle 

 shown, the gas is forced into the carbon dioxide absorption bulb ; 

 here it is allowed to remain for a time, during which the carbon 

 dioxide is absorbed by the caustic potash, after which the gas is 

 drawn back to the graduated bulb and the dift'erence in volume result- 

 ing represents the percentage of carbon dioxide originally present. 

 In a similar way the percentage of oxygen is determined after the 

 carbon dioxide has been removed from the gas, by absorption in the 

 second bulb. Finally, after the removal of both the carbon dioxide 

 and the oxygen, the percentage of carbon monoxide is determined by 

 absorption of the remaining gas in the third bulb. 



With a hand analyzer such as shown, the percentage of carbon 

 dioxide may be determined in the short space of a minute, but to 

 determine oxygen and carbon monoxide in addition to carbon dioxide, 

 will require about 15 minutes. V/e have seen earlier, however, that 

 a knowledge of the percentage of carbon dioxide alone is extremely 

 helpful in bringing about a good furnace practice and only in the 

 exceptional case is it necessary to determine oxygen and carbon 

 monoxide with each analysis made. 



Referring back to the furnace reactions on page 3, it will be 

 noted that the best practice is that which gives the lowest percentage 

 of oxygen and free carbon monoxide gas or, in other words, that 

 which gives the highest percentage of carbon dioxide gas. The 

 reaction (i), resulting in complete combustion, theoretically yields 

 about 20 per cent carbon dioxide, but in furnace practice the reaction 

 is never a complete one and as a result a certain percentage of free 

 oxygen or free carbon monoxide may be present. This means that 



