acid should be added to about three drachms of the bright liquid. If
this precaution is omitted, there is danger of precipitating earthy
phosphates on heating; and should a great excess of acid be employed,
a non-coagulable form of albumen known as syntonin is formed, besides
increasing the likelihood of precipitating mucin. Place the prepared
urine in a narrow test-tube and hold it in a small flame so that the
upper part only of the liquid approaches the boiling point. By this
means very small traces of albumen are easily observed, the
opalescence produced contrasting strongly with the cold and clear
fluid beneath.

The _ferrocyanide test_. Hydroferrocyanic acid yields a precipitate
immediately in the presence of much albumen, and if traces only are
present, in the course of a few minutes. To apply the test, strongly
acidulate with acetic acid, and then add a few drops of recently
prepared potassic ferrocyanide solution. This is one of the most
delicate tests known.

It is often desirable that the percentage of albumen present should be
determined at frequent intervals, in order to note the success or
otherwise of the physician's treatment. These quantitative
determinations, being intended only for comparative purposes, do not
demand any very excessive degree of accuracy, such as would be
difficult to obtain in ordinary practice. The recent method of a
Continental worker. Dr. Esbach, affords indications sufficiently
precise for therapeutical requirements, and is at the same time
extremely easy of application. The filtered acid urine is poured into
the glass tube up to the mark U, and then the special reagent is added
till the level of the liquid stands at R.