Relations to Asphaltic Pavement. 29 



of bitumens, in which he described his manner of separating, 

 partly by distillation and partly by solution, what he supposed 

 were two homogeneous substances from the petroleum, or more 

 properly maltha, of Bechelbronn on the lower Rhine. He 

 found that in making the separation by distillation it was 

 necessary to keep the material heated in an air bath for from 

 45 to 50 hours, and in a note makes this pregnant observation : 

 "■ By this method it is impossible to estimate the two princi- 

 ples of the bitumen; as at this temperature (250° C.) a part of 

 the petrolene is oxidized and passes into the solid state, or 

 asphaltene." These two substances, the petrolene or liquid 

 part, and the asphaltene or solid part into which nearly all 

 bitumens may be resolved in varying proportions, have not 

 received the attention which they deserve, partly because as 

 chemical compounds they are without significance and partly 

 as they are separated from different bitumens, the petrolene 

 in particular, they have very unlike properties. 



On visiting southern California in 1865,* all the natural 

 phenomena attending the passage of petroleum through maltha 

 into asphaltum, were witnessed upon a very extended scale, 

 and I was forced to consider as matters of economic import- 

 ance, many problems that had not hitherto been brought to 

 the attention of technologists. In what manner the changes, 

 everywhere proceeding upon the surface were related to 

 possible changes below the surface, led me to imitate in 

 every respect, save the element of time, the operations of 

 nature as far as possible. I therefore proceeded upon a syn- 

 thetic rather than an analytic line of investigation, and treated 

 the unchanged oil issuing from deep-seated strata, to the 

 action of air and ozone. As the action of these reagents 

 might be explained as due either to the addition of oxygen or 

 to the substraction of hydrogen, I tried the effect of chlorine 

 and found it to be in the main identical with that of the first 

 named gases. The product of these reactions was a brilliant 

 solid, apparently identical with pure asphaltum, and also with 

 Boussingault's asphaltene. 



In 1810, I stated the problem to Prof. J. D. Whitney as 

 follows : " To discover if possible whether asphaltum is formed 

 from petroleum by a change that adds oxygen or substracts 

 hydrogen or both ? To subject several typical varieties of 

 petroleum to the action of ozone under conditions as nearly 

 identical as possible. To study the residues of such action 

 and establish the identity (if such identity exists) between the 

 solid residues and native asphalts. To study the liquid and 

 volatile products of such decomposition." 



* Geological Survey of California, Geology, ii, Appendix, p. 73; Reports 10th 

 Census U. S., vol. x, Petroleum, p. 185. 



