Mr. W. Herapath's Experiments on Oil and Coal Gas. 429 



mentioned, 1 gallon sperm oil would be equal to 131*9 cubic 

 feet of oil gas sp. gr. "900, price 6^. Id. 



But there is another reason why I do not consider their 

 experiments conclusive; — the coal gas was conveyed in a 

 large gasometer from the Company's main, where it must 

 have deposited some naphtha, which would have contributed 

 to its light; while the oil gas must have held a consider- 

 able portion of vapour of oil dissolved in it. There is much 

 moi'e of this than at first sight we should imagine. It has 

 been seen by our 2d set of experiments that oil gas standing 

 4-8 hours over water had lost as much illuminating power 

 as would be communicated by y^th of its weight of oil; 

 and from the circumstance that while the light of coal gas 

 increases very nearly in the same ratio as the density, the 

 light of oil gas goes on much faster, taking two specimens at 

 sp. gr. 876 and TOGO, there would be an increase of 25 per 

 cent, of light more than the density would indicate. If we 

 compress oil gas into a globe, a vapour of oil falls upon the 

 interior of it; if allowed to stand in the flask for taking speci- 

 fic gravities, a dew of oil is perceived in it. Besides the inequa- 

 lity of the two gases from vapour of oil dissolved, thei'e is an- 

 other source of inaccuracy to be guarded against when one 

 gas is transferred, — I mean tlie admixture of common air, a 

 very small portion of which almost destroys its illuminating 

 power. 



Having now data iipon which to calculate, I shall proceed 

 to discuss the eligibility of the gases for the consumer. 



1st, Destruction to the service pipes. Here the advantage is 

 in favour of oil gas, but not to the extent which has been re- 

 presented ; the causes of which destruction are, moisture, sul- 

 phuretted hydi'ogen, and hydro-sulphuret of ammonia. The 

 first would act upon iron services only; where their temperature 

 could be reduced so as to render the gas incapable of holding 

 the moisture which it has dissolved in the gasometer. Its ef- 

 fects are visible, particularly at the foot of iron services, where 

 they rise perpendicularly in exposed situations; for as the 

 water is condensed, it oxidates the interior, and has a tendency 

 to wash the oxide down to the bottom, where it accunuilates 

 and eventually chokes the pij)c ; both gases must be alike 

 subject to this fault. Sulphuretted hydrogen and hydrosul- 

 phuret of ammonia are peculiar to coal gas. It has been shown 

 by Dr. Henry, that the g.ns can be conveniently purified in 

 commerce, so as not to contain more than l-20,000dth of its 

 volume of sulphuretted hydrogen, a quantity too small to re- 

 quire notice. 1 am not inclined to attribute the injury of ser- 

 vices to sulphuretted hydrogen, because we hear ol'none being 



iujuried, 



