Chap. 12] 



MISCELLANEOUS GEOPHYSICAL METHODS 



895 



biinied, in the presence of (purified) air (or oxygen), to water and carbon 

 dioxide. The volume of the latter and, therefore, the reduction of the 

 original volume bears a definite relation to each other if the number of 

 hydrocarbons present and their molecular formulas are known. This pro- 

 cediu'e (combustion and volumetric carbon dioxide determination) is also 

 widely used in those soil-analysis methods in which gaseous members of 

 the paraffin series are measured. 



Fi<:. 12-111). .\.[)]i;it;itu.s for rneiisuring volunio contraction in the combustion of 

 hydrocarbons (partly after Sokolov). 



The combustion of hydrocarbon gases** of the molecular formula 

 ('nH2n+2k (where n is the number of carbon atoms and k may vary fi'om 

 — 3 to +1) is governed by the relation 



C„H2„+2k + ^""^^.Oo = n.COs + (n + k)H20, 



(12-4) 



so that 



O2 = ^r T, COo = nV, and AV = V, 



2 ^ 



(12-5) 



with V as the original \()lume, AV as volume reduction due to combustion, 

 and O2 and C()2 rejiresenting the volumes of these gases. For the mem- 

 bers of the paraffin series, k = 1 and n takes values from to 4, since soil 



XL 



" And of CO, CO2, O2, and Hj, according to L. M. Dennis, Gas Analysis, Chapter 



