52 
barium from the washings of the globe ; thus showing, of 
course, that the oily drops were literally nothing but toler- 
ably strong oil of vitriol. 
The genesis, so to speak, of these drops of sulphuric acid 
is of course easily explained and pretty well understood. 
The sulphur of course originally exists in the coal used for 
gas making, mostly combined with iron as sulphide. In 
the crude coal gas it exists as sulphuretted hydrogen (H 2 S), 
bisulphide of carbon (CS a ), and to a small extent as sulphur 
dioxide (S0 2 ). The greater portion of these compounds of 
sulphur are absorbed by the ammonia liquor which con- 
denses from the gas itself in the scrubbers, and by the lime 
and oxide of iron in the purifiers, through which the gas 
passes on its way to the gasholder ; but nevertheless a suf- 
ficient quantity remains in the gas to produce the effect 
above described and to also produce a bright but very 
objectionable green deposit of sulphate of copper on the 
brass of the gaspipe above the jet I have alluded to. 
The presence of the corrosive substances, sulphur dioxide 
and sulphuric acid in the products of combustion of coal 
gas, has always been known and always acknowledged, and 
yet but little notice of their effects has been taken. It has 
been said, “The quantity is so small and is disseminated 
through such a bulk of other gaseous bodies.” It is as well 
to see what this means. If the amount of sulphur in coal 
gas is reduced to 10 grains per 100 cubic feet, it is considered 
a very pure gas indeed. Manchester gas is supposed to at- 
tain to this degree of purity, and is, I believe as a rule, 
a better gas in this respect than that of many other towns, 
For my own part I should feel inclined to think that only 
a small portion of the gas made in this country uniformly 
reaches this standard. However, say that the gas which I 
burn in my house contains no more than 10 grains of sulphur 
per 100 cubic feet. This means 100 grains, or about a 
quarter of an ounce (about) per 1,000 cubic feet. I find 
