952 



EXPLORATION GEOPHYSICS 



50 grams of each sample are extracted with a solvent such as carbon tetra- 

 chloride in standard Soxhlet extraction apparatus. After removing the 

 solvent, the residue, composed of the organic solids and liquids, is weighed 

 on an analytical balance. When samples are taken from the top one-half 

 inch of soil, the waxes are predominant, while below this depth, the liquid 

 fraction predominates. The sensitive analytical techniques used in the 

 determination of the volatile hydrocarbons are not required here due to 

 the fact that appreciable quantities of waxy and liquid materials are 

 present in near-surface soils ranging from 20-30 parts per million by 

 weight to several hundred parts per million by weight. 



The wax values are calculated from the following equation : 



Parts per million of soil wax =10^ 



grams of soil wax extracted 



grams of pulverized sample analyzed 



PLAN 



Fig. 586. — Soil wax survey. Station interval 1,000 feet indi- 

 cated along profile. Small symbols indicate wells drilled before and 

 large symbols indicate wells completed after the soil survey. 

 (Horvitz, Geophysics, July, 1939.) 



Figure 586 shows the results obtained with samples collected at depths 

 of one-half inch along a profile crossing a producing field in South Texas. 

 It will be noted that, as for the case of volatile soil hydrocarbons, the 

 highest wax values are associated with the edges of the producing area. 



