3821.] 



Proceedings of Public Societies. 



Memale, and arrived at the islands of 

 Malaria, I advanced info the caual 

 of Moez, whence I might view the scat- 

 tered remains of Tanis, and returning 

 to the lake, recognised the Tanitics 

 and Pelnsiac mouths, with the Bogus 

 of Rah I., 



Disembarked upon the shore, I ar- 

 rived through tlie desert at the sides of 

 mount Casius. and tlie day follow- 

 ing ascended that celebrated emi- 

 nenct', wlience I came to Pelusium, 

 that famous key of Eg)-pt, and trusting 

 myself once more to the waves. I visited 

 the islands of Tennis and Tlmua, and 

 passing over the of Meudesian mouth 

 I returned to Damietta. 



Reposing a little, I took diversion up- 

 on the lake, and pi^netrated by the caual 

 of Moez into that of Salable, an i de- 



155 



scending into the desert, I found endless 

 fields ot soda, both vegetable and mi- 

 neral. 



Whence approaching tlie Nile, I ar- 

 rived by the canal of Asmun. at thecity 

 of Beulii, the ancient Meudes ; thence 

 upon the branch Fammeticus to the 

 bed fatal to Louis IX.; and finally 

 returned to Grand Cairo. 



Now that, thanks to the magnani- 

 mous Viceroy of Egypt, thebrave Maho- 

 met Ali, and his faithful minister Bnr- 

 goss JusufF, I am furnished with ample 

 and generous means of penetrating into 

 spaces shut up by the seal of ages, I am 

 preparing to approach the torrid zone, 

 where I hope to shew to Italy that I am 

 not entirely unworthy of belonging lO 

 her. 



PROCEEDINGS OF PUBLIC SOCIETIES. 



I 



ROYAL SOCIETY o/" LONDON. 



TAe Bakerian Lecture, on the Compo- 

 sition and Artaliisis of the inflammable 

 gaseous Compound!! resuUing from the 

 destructive Distillation of Coal and 

 OH, with some Remarks on their rela- 

 tive heating and illuminating Powers. 

 By William Thomas Brande, 

 Esq. Sec. R. S. Prof. Chem. R. I. 



On the Inflammable Gases afforded bij 

 the destructive distillation of pit coal 

 and of oil. 



THE gases used in the following ^ 

 experiments, except where it is ' 

 otherwise expressly stated, were those 

 employed for the common purposes of 

 illumination ; the coal-gas being that 

 supplied from the company's works in 

 Westminster, and the oil gas furnished 

 by the decomposition of common whale 

 oil, in an apparatus erected for that pur- 

 pose by Messrs. Taylors and Mai'tineau, 

 at Apothecaries' Hall. These gases 

 have been submitted to analysis by dif- 

 ferent chemists of emineace; and we 

 are more especially indebted to Dr. 

 Henry for a series of valuable researches 

 respecting their production and compo- 

 sition. It is tiierefore with considerable 

 diffidence that I venture to propose 

 views relating to them in many respects 

 different from those of my predecessors 

 in this important branch of chemical 

 inquiry. 



My first object in the examination of 

 coal-gas, was to ascertain its specific 

 gravity: and I was surprised to find the 

 first that I examined so low as ,44',i0. 

 There was some variation in different 

 specimens; and the specific gravity of 



that prepared in the laboratory of the 

 Royal Institution, and purified in the 

 usiial way by condensation in cold 

 vessels, and passing through lime water, 

 was as high as ,4940, which is the hea- 

 viest that I have yet met with. 



Having been led to consider coal-gas 

 as consisting essentially of the two va- 

 rieties of carburetted hydrogen, I ima- 

 gined that the specific gravity of the 

 light hydrocarhuret must have been 

 estimated too high; I therefore prepared 

 light hydrocarhuret from acetate of 

 potash, and having separated its carbo- 

 nic acid by lime, ifound its specific gra- 

 vity ,6S7; the specific gravity of the 

 gas from stagnant water, according to 

 Mr. Dalton, is ,600, and that from mois- 

 tened charcoal when purified is ,480. 

 It became evident, therefore, that coal- 

 gas could not consist principally of the 

 two hydrocarburets ; nor could the 

 presence of carbonic oxide be suspected, 

 its specific gravity being ,9834. Hence 

 it occurred to me, that the only mode 

 of explaining these apparent anomalies, 

 was to consider coal-gas as a mixture of 

 olefiiint and hydrogen gases; and the 

 following experiments were undertaken 

 with a view to determine this point. 



The analysis of a mixture of hydro- 

 gen with carburetted hydrogen, car- 

 bonic oxide, and carbonic acid, presents 

 peculiar difficulties in the ordinaiy 

 mode of proceeding; and as it oflea 

 requires to be perfornuid in investiga- 

 tions relating to the gases used for illu- 

 mination, it became an object to facili- 

 tate the process, for which I have used 

 the following plan. 



A hundred 



