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27
ciently well known, and the rationale of its action thoroughly
understood; but the instrument which Dr. Odling has placed
upon the table, and has described to you as my ingenious contrivance,
is so different in all its essential particulars from my
instrument, that I disown it, and call it an ingenious perversion
of the apparatus which bears my name. I know from
experience that such an instrument will not discover half the
amount of sulphur that is really present in coal gas; and I
have no doubt that the discrepancies which have lately been
referred to by writers on this subject have been occasioned
by the use of such an instrument as is now upon the table.
The particulars of my instrument, the measurements of the
several parts of it, and the mode of using it, are fullv
described in Mr. Sugg's book on gas manipulation, and if it
be used in a proper manner it will discover ail the sulphur of
the gas; and thus it will be found that the amount of sulphur
may reach to from 30 to 40 grains per 100 cubic feet of gas.
If the presence of sulphur in such quantity in coal gas was
an unavoidable necessity, and could not be reduced by anv
reasonable process of manufacture or purification, it would be
folly to complain of it, other than to show the necessity for
good ventilation where gas is burnt; but this is not the case,
for there are processes of purification which will easily
diminish the amount of sulphur to less than half the usual
quantity. Mr. Ilawksley—whose presence this evening will,
I hope, be useful to us, by his giving us the results of his
large experience in this matter—has shown that, by copiously
washing raw gas with ammoniacal liquor, it is possible to
remove a large proportion of the sulphur compounds of gas
without injuring in the slightest degree its illuminating
power. After this treatment the gas should be deprived of
its sulphuretted hydrogen by means of hydrated oxide of
iron ; and then, while a little ammonia is still remaining in it,
it should be further purified by passing it through dry lime,
which is the slightly moistened hydrate of lime. In this
way the ammoniacal liquor is strengthened to a high degree—
it being rarely less than of 10-oz. strength—by the absorp-