_Detection of Glucose_.--If albumin be present in more than traces, it must be removed by boiling and filtering. * * * * * (1) Haines' Test.--Take about 1 dram of Haines' solution in a test-tube, boil, and add 6 or 8 drops of urine. A heavy yellow or red precipitate, which settles readily to the bottom, shows the presence of sugar. Neither precipitation of phosphates as a light flocculent sediment nor simple decolorization of the reagent should be mistaken for a positive reaction. This is probably the best of the copper tests, all of which depend upon the fact that in strongly alkaline solutions glucose reduces copper oxid to lower grades of oxidation. They are somewhat inaccurate, because they make no distinction between glucose and less common forms of sugar; because certain normal substances when present in excess, especially uric acid and creatinin, may reduce copper, and because many drugs--_e.g._, chloral, chloroform, copaiba, acetanilid, benzoic acid, morphin, sulphonal, salicylates--are eliminated as copper-reducing substances. To minimize these fallacies dilute the urine if it be concentrated, do not add more than the specified amount of urine, and do not boil after the urine is added. {78} _Haines' solution_ is prepared as follows: completely dissolve 30 gr. pure copper sulphate in ½ oz. distilled water, and add ½ oz. pure glycerin; mix thoroughly, and add 5 oz. liquor potassæ. The solution keeps well. (2) Fehling's Test.--Two solutions are required--one containing 34.64 gm. pure crystalline copper sulphate in 500 c.c. distilled water; the other, 173 gm. Rochelle salt and 100 gm. potassium hydroxid in 500 c.c. distilled water. Mix equal parts of the two solutions in a test-tube, dilute with 3 or 4 volumes of water, and boil. Add the urine a little at a time, heating, but not boiling, between additions. In the presence of glucose a heavy red or yellow precipitate will appear. The quantity of urine should not exceed that of the reagent. [Illustration: FIG. 24.--Crystals of phenylglucosazone from diabetic urine--Kowarsky's test. X500.] (3) Phenylhydrazin Test.--_Kowarsky's Method_.--In a test-tube take 5 drops pure phenylhydrazin, 10 drops glacial acetic acid, and 1 c.c. saturated solution of sodium chlorid. A curdy mass results. Add 2 or 3 cc. urine, boil for at least two minutes, and set aside to cool. Examine the sediment with the microscope, using a two-thirds objective. If glucose {79} be present, characteristic crystals of phenylglucosazone will be seen. These are yellow, needle-like crystals arranged mostly in clusters or in sheaves (Fig. 24). When traces only of glucose are present, the crystals may not appear for one-half hour or more. Best crystals are obtained when the fluid is cooled very slowly. It must not be agitated during cooling.