370 Morgan and Tallmon — Occurrence of Bitumen. 



a much greater percentage of oxygen than the figures in the 

 present case. According to Schroiter* dopplerite contains 

 43-03 per cent oxygen. Elaterite appears to be associated 

 sometimes with substances of high oxygen content, which 

 makes the amount of oxygen present in the unpurified material 

 run as high as 35 or 40 per cent. 



On heating above 100° C. many natural asphalts and "breas" 

 froth very characteristically because of the water contained in 

 them. Inasmuch as no frothing occurs on heating this tar to 

 150° C. it is concluded that it contains no appreciable amount 

 of water. This conclusion is supported by the fact that the 

 petroleum ether, chloroform and carbon disulphide solutions 

 are perfectly clear, showing not the slightest turbidity, a cir- 

 cumstance hardly probable if water were present chemically 

 uncombined in the specimen. 



As the temperature is raised above 100° C. the tar begins to 

 decompose slowly. At 150° C. the action is very decided. A 

 volume of inflammable gas, large in proportion to the weight 

 of the substance heated, is liberated. This reaction is com- 

 pleted between 200° C. and 250° C. after which but little 

 decomposition ensues until the temperature rises above that 

 indicated on an ordinary thermometer. 



An attempt was made to determine the boiling-point of the 

 oily liquid left after such heating. It remained unchanged at 

 300° C, and, on heating the tube with a small flame, would 

 creep away from the hotter portions without visibly boiling at 

 360° C. 



The substance remaining after heating to 250° C, on cooling, 

 resembles the original tar in appearance. It is, however, no 

 longer completely soluble in petroleum ether. Only about 

 two-thirds are dissolved by this solvent. Most of the remainder 

 is soluble in carbon disulphide but there always remained a 

 distinct residue which could only be dissolved in chloroform. 

 In these solubility relations it resembles ordinary asphalt 

 possessing a large "petroleum-ether-soluble fraction" ("petro- 

 lene ") and a smaller " asphaltene " fraction soluble in carbon 

 disulphide. The portion soluble only in chloroform is thought 

 by Pechamf to be an indication of "weathering" in those 

 asphalts in which it occurs in appreciable amounts. In this 

 instance it is clearly formed by the action of heat. A combus- 

 tion of 0*0405 gram of the material heated as described gave 

 0*1257 gram carbon dioxide and 0*0452 gram water, indicating 

 84*7 per cent carbon, 12*4 per cent hydrogen and about 3 per 

 cent of oxygen, and sulphur. These percentages correspond 

 with the figures given by asphalts generally on combustion. 



* Wien., Akad. Ber., 285 (1849). 



f Jour. Franklin Institute, No. cli, pp. 114-124 (1901). 



