896 



MISCELLANEOUS GEOPHYSICAL METHODS 



[Chap. 12 



analysis is concerned only with the members from hydrogen to butane. 

 With k = 1, eqs. (12-4) and (12-5) take the form 



and 



CnH2n+2 + ?5^^-02 = nCOa + (n + 1)H20 



02 = ^5^.7, C02 = n7, Ay = ?^.7, 



> (12-6) 



so that, for methane, CH4 + 2O2 = CO2 + 2H2O, and, for ethane, 

 C2H6 + 102 = 2C(>2 + 3H2O, and similarly for the other paraffin hydro- 

 carbons (see Table 86). 



Table 86 

 COMBUSTION OF PARAFFIN HYDROCARBONS 



The volume contraction may be measured by an apparatus of the type 

 illustrated in Fig. 12-116, fashioned after the Burrell methane indicator 

 and consisting of a combustion bulb, B, connected through an equalizing 

 vessel. A, with a capillary and compensator, C. The latter is provided 

 to obviate changes in reading due to changes in volume resulting from 

 variation of temperature. The gas is introduced through the bubblmg 

 tubes and burned by heating the platinum filament. The corresponding 

 volume contraction follows from readings of the capillary before and after 

 combustion. The sensitivity of the apparatus can be increased by using, 

 in place of water, potassium hydroxide, which has the property of ab- 

 sorbing the carbon dioxide and which, therefore, raises the contraction, as 

 shown in Table 86. If methane alone is present, its quantity follows 

 directly from the amount of carbon dioxide developed and, therefore, from 

 the contraction. However, admixtures of heavier hydrocarbons will con- 

 tribute proportionately greater amounts of contraction, since the volumes 

 of carbon dioxide are equal to the numbers of carbon atoms. This type of 

 apparatus, like the second Sokolov field instrument to be described next, 



