of Edinburgh, Session 1885—86. 
799 
(a) 1 hour ebb. 
( b ) 2 hours ebb. 
(c) 3 hours ebb. 
(d) 4 hours ebb. 
As in fig. 5, the two sets of curves are strikingly similar. 
3. On a New Method and Reagent for detecting Chlorides, 
Bromides, and Iodides, in the presence of each other, 
and also in presence of Nitrates and Chlorates. By 
John Jas. Barlow, Manchester Technical School. 
A short time ago I published a method in the Chem. News , vol. 
liii. p. 41, “ On the use of Hydrogen Peroxide as an oxidising agent 
for detecting and estimating Manganese showing the advantages it 
had over other sources of oxygen for oxidation purposes, simply on 
account of the fact, that when using hydroxyl you do not introduce 
any objectionable foreign substance, such as manganese, chromium, 
potassium, lead, &c. 
Since then I have used it with advantage in many other chemical 
operations where oxidation was necessary, amongst others, the sub- 
stance of the present paper — the detection of chlorine, bromine, and 
iodine. The detection of these substances, in the presence of each 
other, has been accepted as (to say the least) troublesome ; and 
numerous papers have been published within the last four years on 
the subject by A. Cavazzi; P. S. Brito, M.B. ; E. Hart; and F. Jones, 
F.R.S.E., though none of the methods given by these chemists can be 
called satisfactory ; the last two may be considered the best, though 
they both introduce foreign substances, and in the last, E. Jones’ 
method, where Mn0 2 is used for oxidising, I could not detect the 
substance, if in small quantity, and its introduction always pre- 
vents the various changes which occur in the solution from being 
observed. 
The following method, which has given entire satisfaction both to 
myself and also to Dr Griffiths, F.R.S.E., Technical School, Man- 
chester, and some of his students, consists in principle of eliminat- 
ing, step by step, as it were, the iodine, bromine, and chlorine in 
succession by means of dilute H 2 S0 4 and a solution of hydrogen 
