458 Scientific Proceedings, Royal Dublin Society. 
(4) Sutphuric Acid.—A mixture of equal volumes of the strong 
acid and water is employed. 
Absorbing Vessel.'.—The vessel in 
which the water under examination 
is mixed with the ferrous sulphate 
and ammonia, and in which, too, the 
mixture is afterwards acidulated 
with sulphuric acid, is an ordinary 
separating vessel of the shape and 
capacity shownin the diagram (fig. 1). 
The exact dimensions, however, are 
of no consequence, provided that the 
vessel holds a sufficient volume of 
water and that the tube forming its 
lower extremity is wide enough to 
contain the quantity of sulphuric 
acid required to acidulate the ammo- 
niacal mixture before titration. 
The Process.—The separating vessel is filled to the brim with 
the water under examination, and for this purpose the authors 
have always employed a glass siphon tube, one 
limb of which is dipped almost to the bottom of 
a Winchester quart bottle (filled originally to the 
brim and then stoppered) containing the sample 
of water, while the other and longer limb is 
connected with a piece of india-rubber tube 
clamped with a pinch-cock. 
A little of the water is first drawn off and the 
separating vessel rinsed with it. The end of 
the rubber tube is then passed to the bottom of 
Fie. 3. the separating vessel, the pinch-cock opened, and 
the water allowed to flow in until the vessel is not only full, but a 
fair quantity has overflowed. In this way the possibility of error 
Fie. 1. 
1 As an ordinary separating funnel is somewhat unwieldy for the purpose of these 
determinations, owing to the length of the tube, Messrs. Baird and Tatlock, of London, 
have constructed for us a special form of apparatus shown in the diagram (fig. 3), 
which is very handy and convenient, and contains exactly } litre. The same firm 
also supplies the whole of the necessary apparatus and reagents for the determinations, 
packed in a box of portabie form. 
