Fill an ordinary test-tube half full of urine, and add a half dram or
more of potassium ferrocyanid solution (1 to 20). After thoroughly
mingling the urine and the reagent, add a few drops of acetic acid
(50 per cent.); then pause for a half minute and note the change.
If albumin be present it will come plainly into view within half
a minute to a minute, in the form of white, milk-like opacity,
diffused throughout the whole contents of the tube. The above method
precipitates all modifications of albumin. On the other hand, it gives
no reaction with phosphates, peptones, mucin, the alkaloids, urates,
or the pure acids. The reaction that sometimes occurs on long standing
between the acid and potassium ferrocyanid should not be mistaken for
albumin. The albuminous reaction appears within half a minute or so,
while the other occurs only after ten minutes to half an hour, and is
mingled with more or less blue coloration.