136 Jnalysia of Scientific Books. 



decomposition, and consequent expansion of the olefiant 

 portion, and therefore attended by a certain diminution of illu- 

 minatin;:^ power, still, as far as economy is concerned, it will be 

 found advantageous to make oil gas at a bright, or cherry-red, 

 heat. 



The next section of Dr. Henry's paper contains the results 

 of his experiments on coal gas, which are conducted with his 

 usual skill and patience, but the analyses are so much affected 

 by the questions discussed in the concluding section, that we 

 shall prefer employing our remaining space in calling the reader's 

 attention to the author's " inferences respecting the composition of 

 that part of the gas from coal and oil, which is condensed by contact 

 with chlorine." By a variety of experiments, Dr, Henry con- 

 siders it as proved, that that portion of oil and coal gas, which 

 is condensible by chlorine, (light being excluded), is of a spe- 

 cific gravity of 1.4 to 1.2, and consequently, that it is not pure 

 olfiantgas. Again, both Dr. Henry and Mr. Dalton, agree 

 that the portion of oil and coal gas condensible by chlorine, 

 requires for its entire combustion not three volumes of oxygen 

 (which would indicate olefiant gas,) but four volumes and a 

 half; so that as our author himself remarks — 



" It is evident from these facts that the aeriform ingredient of oil gas 

 and coal gas, which is reducible to a liquid form by chlorine, is not identical 

 with the olefiant gas obtained by the action of sulphuric acid on alcohol, 

 but considerably exceeds tiiat gas in sp:'citic gravity and combustibility. 

 Two views may be taken of its nature ; for it may either be a gas sui 

 generis, hitherto unknown, and constituted of hydrogen and charcoal in dif- 

 iTerent proportions from those composing any known compound of those 

 elements ; or it may be merely the vapour of a highly volatile oil, mingled 

 in various proportions with olefiant gas, carburetted hydrogen, and the 

 other combustible gases. Of these two opinions, Mr. Dalton is inclined 

 to the first, considering it as supported by the fact that oil gas, or coal gas, 

 may be passed tlirough water, without being deprived of the ingredient 

 in question ; and that this anomalous elastic fluid is absorbed by agitation 

 with water, and again expelled by heat or other gases, unchanged as to its 

 chemical properties, as we have both satisfied ourselves by repeated experi- 

 ments. On the other hand, I have found that hydrogen gas, by remaining 

 several days in narrow tubes in contact with fluid naphtha, acquires the 

 property of being affected by chlorine, precisely as if it were mixed with a 

 small proportion of olefiant gas ; and I am informed by Dr. Hope, that oil 

 gas, when forcibly compressed in Gordon's portable gas lanip, deposits a 

 portion of a highly volatile essential oil. The smell also of the liquid which 

 js condensed on the inner surface of a glass receiver, in which oil gas or 

 coal gas has been mixed with chlorine, denotes the presence of cJiloric 

 ether, evidently however mingled with the odour of some other fluid, which 

 seems to me to bear most resemblance to that of spirit of turpentine. This 

 part of the subject is well worthy of further investigation ; but having de- 

 voted to the inquiry all the leisure which I am now able to command, I must 

 remain satisfied at present with such conclusions as are safely deducible 

 from the foregoing investigation." 



We entirely agree with Dr. Henry that this subject deserves 

 further investigation, and as no one can be better qualified for 

 its prosecution than himself, we trust that he will resume and 

 complete that which he has so ably commenced. It is not only 

 interesting as an abstract chemical inquiry, but may also prove 

 important in its relations to the economy of gas illumination. 



C. 



