300 Experiments on Mr. Duahlke’s Filter. 
readings for the twenty-four hours, and forms the datum 
line from which the ordinates to the curves are measured. 
If we wish to tabulate the numerical values of the ordinates 
from these curves a correction has to be applied to each 
ordinate, depending on the distance of this datum from the 
zero line, or line that would be made by the reflected dot 
when the pendulum was vertical. I submit a few of the 
curves for your inspection, and hope, at some future time, 
to bring before you some results obtained by this apparatus, 
and describe the manner in which the indications obtained 
are converted to absolute measure in adopted units of 
force. 
ART. XXVI.—Ewperiments on Mr. Julius Dahlke’s Filter. 
By Mr. J. Cosmo NEWBERY. 
[Read 9th December, 1867.] 
At the last meeting of this Society a paper was read by 
Dr. Neild for Mr. Julius Dahlke, describing a new filter, 
which was stated to be peculiarly adapted for filtering 
water containing organic matter, and water which, having 
passed through lead pipes or vessels, contained salts of lead. 
And the statement that it would remove acetate of lead, and 
some other salts from solution without chemical action was 
so remarkable, and of so much importance, that I gladly 
undertook to try some experiments with the filter and 
report the results to you. I am very much pleased to be 
able to corroborate all Mr. Dahlke’s statements, and indeed 
go further. Upon receiving the filter I poured into it solu- 
tions of sulphate of magnesia and common salt, and to my 
astonishment found only traces of these salts in the filtrate, 
so small that they could only be detected chemically. These 
salts were followed by strong acetic and hydrochloric acids, 
with like results, the water from each being absolutely taste- 
less. I finally added strong yellow sulphide of ammonium, 
which passed through as pure water. Upon inverting the 
filter and pouring in hot water, the sulphide of ammonium 
was discharged undecomposed, showing that though it fol- 
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