some < if the Principles of Vegetables into Bilumen. 131 



§ VI. 



The powerful action which alcohol exerts on most of the 

 resins may justly be regarded as forming a marked distinc- 

 tion between those substances and the bitumen?. But, as 

 soiiie of the bitumens are acted upon by alcohol in a slight 

 dcsrree, I was desirous to ascertain whether a small portion 

 of^resin was contained in any of these; or, if that was not 

 the case, I wished to determine the nature of the substance 

 which could be separated, although very sparingly, by this 

 menstruum. I therefore made the following comparative 

 experiments on the soft brown clastic bitumen from Derby- 

 shire; on the genuine asphaltum ; on very pure cannel coal ; 

 3nd on the conmion pit coal. 



100 grains of each were digested with three ounces of 

 alcohol, in matrasses placed in warn! sand, during live days, 

 some alcohol being occasionally added, to supply the loss 

 caused by evaporation. After the above-mentioned period 

 had elapsed, the liquid contained in each matra.-;3 was poured 

 into separate vessels, 



1. The alcohol which had been digested on the clastic 

 bitumen was not tinged, nor, when spontaneously evapo- 

 rated, did it leave any film or stain on the glass, 



2. From asphaltum the alcohol had extracted a yellow 

 tincture, which, in some situations, appeared of a pale olive 

 colour, and, being spontaneously evaporated, a thick brown 

 liquid was dcposTtcd, in sniall drops, on the glass ; these 

 drops did not become hard alter two months, and possessed 

 the odour, and every other property, of pctroleuiTi. The 

 asphaltum had lost in weight about one grain and a half. 



3. The e.annel coal had communicated a pale yellow tint to 

 the alcohol, which, in the manner above described, was a.-- 

 qertained to be caused by petroleum ; but, from the small - 

 ncss of the quantity, tlie weight could not be determined. 



4. The alcohol which had'bcen digested on pit coal had 

 not assumed any colour ; but, by spontaneous evaporation*, 

 it left a fdm on the glass, which, by its odourj was also 

 found to be petrolcmn. 



By these experiments we find that the action of alcohol 

 on the bitumens is very slight; and that the small porticn 

 which may thus be extracted from some of thtm is petro- 

 leum. In these, the process of bituminization (if I may be 

 allowed to employ such a tfcrn)) ajijiears to have been com- 

 pleted, whilit in the Bovey co.d, ai\d especially in the siib- 



• Sjiontiincou'; evaporation, Ijy cxporure to the :iir, vva<! pnir.lovc d iu 

 Uic^c txpcriiiiLius for rta.-jr.s v.liicli miiit be suflicicmly olvious. 



' t;4 ^-^ "■''-<'- 



