The nitric acid test.  Heller’s contact method, which can also be used with the last-described reagent, is the best mode of applying the old-fashioned and favorite test with nitric acid.  To 5 volumes of a filtered saturated solution of magnesic sulphate, prepared by dissolving 10 parts of the salt in 13 parts of distilled water, add 1 volume of strong nitric acid, and label “Sir W. Roberts’ nitric acid reagent.”  A couple of drachms of bright filtered urine is allowed to float on an equal quantity of this solution in a test tube; care being taken that the contact line is sharply defined.  In a period of time varying from a few seconds to a quarter of an hour, according to the amount of albumen present, a delicate opalescent zone forms at the point of junction, and if mucin also is present, a more diffused haze higher up in the urine.  Special attention should be given to the position of the opacity.  In some concentrated urines a belt of urates will appear at the line of demarkation; but these dissolve on warming.  Moreover, owing to the dilution necessary in the mode of applying Galippe’s picric acid test, they are not so readily shown by the latter.  A 1/2 oz. glass syringe can very conveniently be substituted for a test tube in making analyses according to Heller’s method.  Some of the urine should be drawn up, and then an equal volume of the reagent.  On setting aside, the albumen ring will rapidly develop.

The boiling test.  This method also is very delicate and valuable.  It depends on the well-known property possessed by many proteids of coagulating under the influence of heat.  The urine should have an acid reaction to test paper; if alkaline, it must be cautiously neutralized with dilute acetic acid.  In either case a single drop of strong acetic 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.