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EXAMINATION OF THE URINE.

Directions for Collecting Twenty-four Hour Urine.

Pass the urine at 7 a.m. and throw it away.

Save all the urine passed after this up to 7 a.m. the next day. Pass the urine exactly at 7 a.m., and add it to what has previously been passed.

Qualitative Sugar Tests.

(1) Fehling's Test:—Boil about 4 c.c. of Fehling's[1] solution in a test tube, and add to the hot Fehling's an equal amount of urine, a few drops at a time, boiling after each addition.

A yellow or red precipitate indicates sugar.

For practical purposes in the following of a diabetic's daily urine, this is a valuable test, and the one which we always use.

(2) Benedict's Test:—To 5 c.c. of Benedict's[2] reagent add 8 drops of the urine to be examined. The fluid is boiled from 1 to 2 minutes and then allowed to cool of itself. If dextrose is present there results a red, yellow, or green precipitate, depending upon the amount of sugar present. If no sugar is present the solution may remain perfectly clear or be slightly turbid, due to precipitated urates.

This is a more delicate test than Fehling's.

Quantitative Sugar Tests.

(1) The Fermentation Test:—The fermentation test is the simplest quantitative test for sugar, and is quite accurate enough for clinical work. It is performed as follows: The specific gravity of the 24° urine is taken, and 100 c.c. of it put into a flask, and a quarter of a yeast cake crumbled up and added to it. The flask is then put in a warm place (at about body temperature) and allowed to remain over night. The next morning a sample of the fermented urine is tested for sugar. If no sugar is present the urine is made up to 100 c.c. (to allow for the water that has evaporated) and the specific gravity taken again. The number of points loss in specific gravity is multiplied by .23, and this gives the percentage of sugar in the urine.

(2) Benedict's Test:—The best quantitative test for dextrose (excepting polariscopic examination, which is too complicated for ordinary work) is Benedict's test.

It is performed as follows: Measure with a pipette 25 c.c. of Benedict's solution into a porcelain dish, add 5 or 10 gm. (approximately) of solid sodic carbonate, heat to boiling, and while boiling, run in the urine until a white precipitate forms.

Then add the urine more slowly until the last trace of blue disappears. The urine should be diluted so that not less than 10 c.c. will be required to give the amount of sugar which the 25 c.c. of reagent is capable of oxidizing.

Calculation: 5, divided by the number of c.c. of urine run in, equals the per cent. of sugar.

Benedict's quantitative solution is prepared as follows: Dissolve 9.0 gm. of copper sulphate in 100 c.c. distilled water. (The copper sulphate must be weighed very accurately.) Dissolve 50 gm. anhydrous sodic carbonate, 100 gm. sodic citrate, and 65 gm. of potassium sulpho cyanate in 250 c.c. of distilled water.

Pour the copper solution slowly into the alkaline citrate solution. Then pour the mixed solution into the flask without loss, and make up to 500 c.c.; 25 c.c. of this solution is reduced by 50 mgm. of dextrose, 52 mgm. of levulose or 67 mgm. of lactose.

(3) Acetone Test:—To 5 c.c. of urine in a test tube add a crystal of sodium nitro prusside. Acidify with glacial acetic acid, shake a moment, and then make alkaline with ammonium hydrate. A purple color indicates acetone.

(4) Diacetic Acid Test:—To 5 c.c. of urine in a test tube add an excess of a 10% solution of Ferric chloride. A Burgundy red color indicates diacetic acid.

Quantitative Test for Ammonia.

To 25 c.c. of urine add 5 c.c. of a saturated solution of potassium oxalate and 2 to 3 drops of phenolphthalein.

Run in from a burette decinormal sodic hydrate, to a faint pink color. Then add 5 c.c. of formalin (40% commercial) and again titrate to the same color.

Each c.c. of the decinormal alkali used in this last titration equals 1 c.c. of n/10 ammonia, or .0017 gm. of ammonia. Multiply this by the number of c.c. n/10 sodic hydrate used in the last titration; this gives the number of grams of ammonia in 25 c.c. urine.

Note:—The potassium oxalate and the formalin must both be neutral to phenolphthalein.