508 Hev. J. Barlowy on Mineral Candles, S^c. [March 26. 



much light as a candle weighing ^th lb., made of spermaceti or of 

 stearic acid. Its property of fusing at a very low temperature 

 into a transparent liquid, and not decomposing below 600° Fahr. 

 recommends this substance as the material of a bath for chemical 

 purposes. As to the fluids obtained in the second distillation, 

 already described, they all possess great lubricating properties ; and, 

 unlike the common fixed oils, not being decomposable into an acid, 

 they do not corrode the metals, especially the alloys of copper, 

 which are used as bearings of machinery. This aversion to chemi- 

 cal combination, which characterizes all these substances, affords, 

 not only a security against the brass-work of lamps being injured 

 by the hydro-carbon burnt in them, but also renders these hydro- 

 carbons the best detergents of common oil lamps. It is an interest- 

 ing physical fact, that some of the non-volatile liquid hydro-carbons 

 possess the fluorescent property which Stokes has found to reside 

 in certain vegetable infusions. 



3. Chemical constitution of these hydro-carbons. — On this 

 subject, there will be found a short memoir by Warren de la Rue, 

 and Hugo Miiller, in the Proceedings of the Royal Society, Vol. 

 viii., page 221. The researches referred to in that memoir are 

 nearly completed. The principal constituents of the Burmese 

 naphtha, are — (a), (the largest in proportion) a substance identical 

 in composition with either the hydrurets or the radicals of the 

 ethyle series ; (6) Substances of the benzole series, forming a com- 

 paratively small portion. It has, however, been ascertained that 

 some of the hydro-carbons of this aromatic series differ in their 

 chemical and physical properties from the analogous members of 

 the same series obtained from the usual sources. This difference 

 is most strongly marked in the case of cumole and its higher 

 homologues of the benzole series,* (c) the colophene series already 

 adverted to. 



An important characteristic of the Burmese naphtha is its being 

 almost entirely destitute of the hydro-carbons belonging to the 

 olefiant-gas series. 



[J. B.] 



♦ In illustration of this view may be cited, Church's discovery of a para- 

 benzole in coal tar, boiling at 185° Fahr., and not solidifying at 32°. 



