Clinical, Significance

In the urine it exists in the proportion of 15 to 20 parts in 1000; in the blood, .016 parts in 1000.

Tests For Urea

Urea crystallizes in colorless prisms, very soluble in water, and behaves like an alkaloid, combining readily with nitric and oxalic acids to form salts. Both of these salts may be precipitated in colorless plates from concentrated urine by adding nitric or oxalic acid. In the course of many diseases it is important to estimate the amount of urea excreted day by day.f

A rough test is furnished by the readiness with which crystals of the nitrate of urea form after adding nitric acid. These crystals do not form readily unless there is an excess of urea. Add to the urine one-fourth its bulk of nitric acid in a test-tube immersed in cold water, and the relative proportion of crystalled nitrates is easily calculated.

Example

Ounces. Quantity of urine in twenty-four hours.................... 46

Sp. gr. of the urine.........1020

Sp. gr. liq. sod. chlor.........1042

(Calculated) Sp. gr. mixed (1042x7 + 1020%8=) .....1039.2 +

(Actual) Sp. gr. mixture after reaction...................1036.2

1039.2 - 1036.2=3; 3x3 1/2 = 10 1/2 grs. of urea to the ounce of urine; 10 1/2x46 = 483 grs. of urea passed in twenty-four hours.*

Phosphates

Two kinds of phosphates are found in the urine - phosphate of lime and ammonio-mag-nesian, or triple phosphates. About six parts in 1000 of normal urine consists of phosphates; when they are in excess, the urine is generally of a light color. These salts are derived from the food and tissues, and are united with the organic, nitrogenized, proximate principles. Their quantity in the urine depends on the food eaten and the drain on the nervous system from study or sexual excesses.

*Prof. Charles F. Stillman. † Prof. S. E. Woody.

‡ Russel and West. *Prof. S. E. Woody.

Clinical Import

When excreted in excess there is danger of phosphatic calculus. Disease changes its proportions. Increased elimination occurs in inflammatory diseases of the nervous system, acute mania, delirium tremens, paralysis, diseases of the bones and rickets. It is generally diminished in Bright's disease, gout, rheumatism and pneumonia.

Tests

Heat gives a cloudy precipitate, which nitric acid dissolves. The phosphates are deposited when the urine becomes alkaline and ferments. Under the microscope, phosphate of lime is amorphous. The triple phosphates occur in rhombic prisms, which readily dissolve in acetic acid, while oxalate of lime crystals do not.

Quantitative

A rough estimation is made by making some urine alkaline with ammonia and adding an ammonio-magnesian solution to it. If the amount already in the urine is normal, a precipitate at once occurs; if the normal amount is lacking, this precipitate is delayed.*

*Prof. Charles F. Stillman.

Examination Of Urinary Deposits

1. Deposit white, see 2; colored, see 6, 7 and 8.

2. Deposit soluble when heated: Urates.

3. Deposit soluble in ammonia: Cystin.

4. Deposit soluble in acetic acid: Earthy phosphates.

5. Deposit insoluble in acetic acid: Oxalate of lime.

6. Deposit crystalline: Uric acid.

7. Deposit amorphous, faintly colored, readily soluble whea heated: Urates.

8. Deposit strongly colored, slowly soluble when heated: Urates tinged with purpurine.

9. Deposit greenish-yellow, easily diffused by agitation: Pus.

10. Deposit ropy and tenacious: Mucus.