ALCOHOI, CHECK EXPERIMENTS. 99 



One gram of a mixture of ethyl hydroxide and water containing 

 90.77 per cent of absolute alcohol will give 1.735 grams of carbon 

 dioxide and 1.066 grams of water, resulting from the combustion of 

 the alcohol molecule, in addition to the 0.092 gram of preformed 

 water present in each gram of the mixture, and thus the total amount 

 of water resulting from the combustion and vaporization of one gram 

 of 90.77 per cent alcohol is 1.066 -(-0.092 = 1.158 grams. 



If one gram of the 90.77 percent alcohol yields 1.735 grams of carbon 

 dioxide and 1.066 grams of water, the amount of oxygen involved in 

 the reaction is readily determined by adding the weights of the carbon 

 dioxide and water and subtracting the original weight of the alcohol used. 



To simplify calculations, three logarithmic factors are computed, 

 which, when added to the logarithm of the weight of alcohol burned, 

 yield the logarithm of the total theoretical amounts of carbon dioxide, 

 water, and oxygen involved in the combustion. These factors obvi- 

 ously vary with the percentage of alcohol used, and consequently the 

 specific gravity of a rather large amount (5 to 6 liters) is taken and 

 the alcohol carefully preserved in a well-stoppered bottle for use ex- 

 clusively in alcohol check experiments. 



AI.COHOI, LAMP. 



In earlier experiments, when oxygen was not determined, it was pos- 

 sible to introduce through the food aperture a small alcohol lamp and 

 change it at the end of a period for another one without material alter- 

 ation of the water and carbon-dioxide content of the air inside the 

 chamber ; but the problem became complicated when the determination 

 of oxygen was undertaken, and this simple method was no longer 

 sufficient. Consequently a special form of lamp was devised by means 

 of which the alcohol could be put into the chamber without disturbing 

 the food aperture or the volume of air inside the chamber. The lamp 

 is pictured in figure 22. 



The reservoir of the lamp is a bottle with an opening on one side 

 near the bottom and another in the center of the bottom. The burner 

 is of the ordinary round wick, kerosene, Argand type, and is attached to 

 the neck of the bottle by means of a short length of large rubber tubing. 

 The wick is purposely long enough to reach nearly to the bottom of 

 the bottle. The reservoir is filled with alcohol through a rubber tube 

 extending from the hole in the side of the bottle through a small 

 orifice in the outer door of the food aperture to the supply on the out- 

 side. A glass tube of small diameter, bent like a U tube, with a long 

 and a short arm, and with the latter inserted in the opening in the 

 bottom of the bottle, serves to indicate the level of the alcohol in the 



