I have devised, and am practising, a very convenient titra-
tion of urea, the ammonia from which is Nesslerised, The
method is the following : —

Ten cubic centimeters of a solution of caustic potash, free
from aU traces of ammonia (strength 10 grammes of solid
potash in 100 c. c. of water), are placed in a small flask-retort
(capacity about 100 c c), which is heated in an oil-bath.
Into the potash-solution, either one cubic cent, of urine,
accurately measured out, or else 10 c. c. of a one-per-cent
solution of urine, is dropped, and the whole heated to 150**
Cent in the oil or spermaceti bath, until the ^tash inside



I30



WATER-ANALYSIS.
the flask-retort has nearly dried up. During this operation
the flask-retort is neatly connected with a small Liebig's
condenser, vide fig.
When the contents of the flask-retort appear nearly dry —
i.e., when a temperature of 150* Cent, has been maintained for
a short period in the interior of the flask — ^the temperature




should be lowered. This is done by getting the flask out of
the hot oil or spermaceti, and either the oil-bath may be
lowered down away from the flask, or else the flask, which is
to be maintained in firm connection with the Liebig's con-
denser, may be raised out of the oil.
If the Liebig's condenser be held by a proper kind of
clamp, made of metal lined with cork, and very firm and con-
venient, this raising up of the apparatus wiU be found to be
quite easy.
