98 A RESPIRATION CALORIMETER. 



in position in the water bath. The water is constantly stirred and the 

 temperature frequently noted, with due allowances for the calibra- 

 tion correction of the thermometer. When the temperature of the 

 whole mass has reached 15.6, the level of the alcohol in the stem is 

 brought to the graduation at 42.5. The removal of alcohol is readily 

 made by means of a finely drawn-out glass tube and small strips of 

 bibulous paper, and all alcohol adhering to the upper part of the stem 

 is carefully absorbed by these means. After the proper adjustment of 

 the level of the liquid, the pyknometer is removed, carefully dried, and 

 weighed. The increase in weight is the absolute weight of 50 cc. of 

 the alcohol, and this number, divided by 50, gives the specific gravity 

 of the solution direct. The expansion of the alcohol after removal 

 from the water bath causes the enlargement of the stem to become 

 partly filled with alcohol, but obviously this in no wise affects the 

 weight. 



ALCOHOLOMETRIC TABLES. 



From the specific gravity the percentage of alcohol may be obtained 

 from standard alcohol ometric tables. Dr. E. R. Squibb in a personal 

 letter recommended as especially accurate a table published in his 

 Ephemeris. 1 A more recent alcoholometric table prepared by Morley * 

 is also excellent. 



FACTORS FOR ACTUAL AMOUNTS OF CARBON DIOXIDE, WATER, AND OXYGEN. 



The combustion of pure ethyl hydroxide may be expressed by the 

 following equation : 



C 2 H 6 + 3 2 = 2C0 7 -f- 3 H 2 0. 



From the molecular weights 3 of ethyl hydroxide, carbon dioxide, and 

 water and the atomic weight of oxygen it can be readily calculated that 

 one gram of ethyl hydroxide when completely burned yields 1.911 

 grams of carbon dioxide and i . 1 74 grams of water, requiring for its 

 combustion 2.085 grams of oxygen. 



Since pure ethyl hydroxide is never used, however, but rather 

 alcohol diluted with about 10 per cent of water, it is necessary to 

 take into consideration the percentage of alcohol used. In general 

 the alcohol is not far from 91 per cent ethyl hydroxide by weight, 

 and in the alcohol check experiment given on page 102 the alcohol 

 used consisted of 90.77 per cent of ethyl hydroxide. 



1 Ephemeris, 1884-85, part 2, pp. 562-577. 

 'Journ. Am Chem. Soc. (1904), 26, p. 1185. 

 8 Atomic weights used are given on page 82. 



