CHEMICAL METHODS 



941 



ammonia, the sample is circulated through a trap immersed in liquid air. 

 At this temperature, methane and ethane are not condensable and therefore 

 pass through the trap and are converted to carbon dioxide and water by 

 combustion. The carbon dioxide is collected and by means of a McLeod 

 gauge its pressure is determined. This is called the ligJit fraction and is 

 expressed in per cent by volume of sample analyzed. 



The condensable portion of the sample, called the heavy fraction, is 

 directly measured w^ith a McLeod gauge and is believed to consist of a 

 mixture of complex hydrocarbons and their derivatives. The heavy fraction 

 is calculated and expressed in per cent by volume of sample analyzed. 



In conducting surveys, the analytical values are found to range from 

 less than .0005 per cent to about .03 per cent by volume. 



Results of Gas Surveys, — The Russian workers, as well as Laub- 

 meyer, reported hydrocarbon distribution patterns in which the greater 



^^, 



X Methane 



Ethane and higher 

 Hydrocarbons 



Fig. 578. — Idealized profiles showing significant hydrocarbon patterns as reported by Russians. 

 (Howard, Oil and Gas Journal.) 



