380 Dr Reichenbach on Petroleum or Mmeral Oil. 



or to avoid having the outer portions aggregated together and 

 exposed to a heat which goes on increasing, and which then causes 

 the formation of the first products of dry distillation, and in this * 

 manner gives rise to an entirely false result. That matter, which 

 passes over with the watery vapour, is, it is true, only the pro- 

 duct of the tension of petroleum at 100* C. ; but one can be as- 

 sured by this procedure, that only watery, and no dry distilla- 

 tion's products are obtained. The coal which remains loses no- 

 thing of its external characters except the lustre of its fracture. 



If we wish to proceed further, and to inquire how petroleum 

 has been formed, and whence it derives its origin in coals, I be- 

 lieve 1 may venture to attempt a reply. In all my earlier la- 

 bours with mineral oils, I never trusted to the purity of the sub- 

 stances obtained by purchase, as it always appeared to me that 

 the mineral oil sold had the smell of turpentine, and that it was 

 rendered impure by it. The impossibility of making mineral- 

 oil free from soot, in which peculiarity it is so remarkably dis- 

 tinguished from Eupion, strengthened my mistrust. I was not 

 a little surprised to find the same turpentine smell in that mine- 

 ral which I myself had prepared, and of whose purity I was 

 convinced. This odour was particularly distinct when I rubbed 

 some drops between my hands. I perceived that the turpentine 

 odour belonged in fact, up to a certain point, to the finest pe- 

 troleum, and that it was the less mixed with other odours the 

 purer the substance was. Upon comparing further the physical 

 and chemical properties of natural and my own artificial petro- 

 leum with those of turpentine-oil, I obtained the following results. 



In transparency, absence of colour, tint of the accidental tinge 

 of yellow colour, and mfluidity, they are precisely alike. The 

 smell seems to approach in a remarkable manner, and is merely 

 altered by various accidental mixtures ; as turpentine-oils from 

 different pines smell somewhat differently, so do the petroleums 

 from various sources vary in the same manner : all have, how- 

 ever, a more or less distinct turpentine-oil smell, which is most 

 distinct when the substance is rubbed between the hands. In 

 taste the artificial mineral oil and the rectified turpentine-oil ap- 

 proach very nearly : that of the latter is stronger, but of the same 

 description. The specific grav'tty of turpentine-oil is given in 

 elementary works, as from 0.79 to 0.87 ; this gives a mean of 

 0,83 which is nearly the specific gravity of the mineral-oil from 



