210 Drs. Christison and Turner 07i Oil and Coal Gas. 



we suspect that a part of the inconvenience found by jewellers 

 to attend the use of coal gas arises from this cause. 



The most formidable of the compounds of sulphur present 

 in coal gas is sulphuretted hydrogen. The presence of this 

 gas is hurtful in two ways. If it escape unburnt, it offends by 

 its insupportable odour, and attacks silver and paint with great 

 readiness. When consumed, it forms sulphurous and sul- 

 phuric acids, which may injure the health if habitually inspired, 

 and act chemically on various substances, as on iron and steel. 

 Hence the necessity of removing it entirely from coal gas. On 

 this subject two important questions naturally occur, to both 

 of which we can give a decisive answer. 1st, Can sulphuretted 

 hydrogen be wholly separated from coal gas? and 2dly, when 

 it is removed, Can coal gas be regarded as perfectly free of 

 sulphur ? 



We are satisfied that sulphuretted hydrogen may be wholly 

 removed; for we have repeatedly examined the Edinburgh 

 coal gas by the most delicate tests, without detecting a trace 

 of it. Of'course we do not vouch that it is always equally 

 pure, because the least neglect on the pai't of the workmen 

 must inevitably cause some sulphuretted hydrogen to escaj)e 

 into the pipes. It is equally certain, however, that coal gas, 

 when completely free of sulphuretted hydrogen, still contains 

 sulphur. On burning a small jet of coal gas, free from sul- 

 phuretted hydrogen, so as to collect the fluid formed during 

 the combustion, the presence of sulphuric acid was uniformly 

 detected, demonstrating the existence of some compound of 

 sulphur. What that compound is has not yet been ascer- 

 tained; but from its peculiar unpleasant odour, and the cir- 

 cumstances under which it is generated, the sulphur is most 

 probably in combination with carbon, either in the form of the 

 volatile liquid (sulphuret of carbon, as Mr. Brande conjec- 

 tures), or, what is perhaps more likely, as a gaseous compound, 

 containing a less proportion of sulphur than exists in that li- 

 quid. 



In whatever state of combination the sulphur may be, it 

 does not affect the salts of lead like sulphuretted hydi'ogen ; 

 nor does it act so readily, if at all, on polished silver and gold. 

 Hence the gas which contains only this impurity will be less 

 injurious when any of it escapes unburnt, than such as con- 

 tains sulphuretted hydrogen ; but since it uniformly yields 

 acid vapours during its combustion, one part of the objection 

 remains in full force. 



These various objections, whatever weight they may have, 

 apply to coal gas only. 



XXX. A 



