Materials Included In Kit

Additional Materials Required

Prelab Preparation

The specific gravity tests should be done as an all-class data collection/demonstration. Enlist student volunteers to conduct the procedure on each of the five urine samples. As each test is complete, have students read the specific gravity reading to the entire class. Rinse and dry the test tube in between each test. Prior to class, label additional containers for dispensing the urine samples so that the urine samples for the specific gravity test can be used for additional tests.

Be sure to adjust the specific gravity of the urine samples to yield the results desired. The specific gravity can be lowered by adding distilled water to the samples. The sample data does not reflect specific readings but rather possible trends you can create.

Safety Precautions

Even though the simulated urine samples do not contain any actual body fluids, the samples should be treated as if they do. Biuret test solution contains copper(II) sulfate and sodium hydroxide and is a corrosive liquid. It is moderately toxic by ingestion and is dangerous to skin and eyes. Benedict’s solution contains copper(II) sulfate, sodium citrate and calcium carbonate; it is moderately toxic by ingestion and a skin and body tissue irritant. Hydrochloric acid is severely toxic by ingestion and is corrosive to skin and eyes. Iodine solution contains iodine and potassium iodide and is an eye and skin irritant; it will stain skin and clothing. Avoid contact of all chemicals with eyes and skin. Wear chemical splash goggles and chemical-resistant gloves and apron. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All of the resulting solutions and excess Benedict’s reagent may be disposed of down the drain with plenty of excess water according to Flinn Suggested Disposal Method #26b. Excess biuret solution may be neutralized with acid and then disposed of according to Flinn Suggested Disposal Method #10.

Teacher Tips

• Enough materials are provided in this kit for 30 students working in pairs, or for 15 groups of students. The laboratory activity can reasonably be completed in one 50-minute class period. (Note: The amount of urine sample provided for each individual assumes a single test for specific gravity or the continual reuse of the sample for this test.)

• The specific gravity and pH results may vary from batch to batch.
• If you want all students to collect their own data on specific gravity and have the experience of using a hydrometer, you can devise a way to “pass” the hydrometer from group to group or set up a central specific gravity testing area reusing the urine samples.
• The urine samples can be spiked with a fluorescent dye prior to the lab. During the lab a UV light can be used to reveal any contamination of urine in the lab.
• The urine samples can be further altered for other variables (see References). Urine testing strips would also work to test samples.
• Very small quantities are required for the tests in this laboratory. Small dispensing bottles may be used if available.

Sample Data

Answers to Questions

1. What individual has the most “normal” overall urine test results? Explain your choice.
   

   Individual V has no protein or sugar in the urine and other factors are in the “normal” range.
   

2. Which individual most likely has diabetes or should be tested further for diabetes? Explain your choice.
   

   Individual Y has sugar in the urine which is a likely predictor of the possibility of diabetes. Further testing should be done.
   

3. Discuss the urine test results of individual X. What results indicate the need for further testing?
   

   Individual X has very acidic urine as well as protein in the urine. Neither may be significant, but the two factors coupled together would be justification for further testing.
   

4. Compare urine test results for individual V and individual W. Should further testing be done? Explain.
   

   Both individuals have fairly “normal” looking urine tests except for the presence of protein in person W’s urine. Person W should have further tests to determine the origin of the protein in the urine.

References

Hole, J. W. Human Anatomy and Physiology; Wm. C. Brown; Dubuque, IA, 1990.

Shmaefsky, B. R. The American Biology Teacher; 1990, 52, 170–172.

Shmaefsky, B. R. The American Biology Teacher; 1995, 57, 428–430.

Introduction

We must maintain a chemical balance in our body fluids in order to maintain good health. Our kidneys function to help maintain this internal balance. The chemical makeup of the body’s liquid waste (urine) can be a good indicator of internal body chemistry and possible imbalances.

Concepts

• Urinalysis

• Homeostasis

Background

Normal urine usually varies in color between a straw yellow and an amber transparent color and possesses a characteristic odor. Urine color and odor vary considerably from time to time according to the ratio of solutes to water in the urine. Many internal body functions can contribute to the solute-to-water ratio. Cloudy urine sometimes reflects the secretion of mucin from the urinary tract lining and is not necessarily an indication of a problem. In general, however, cloudy urine should be tested further to determine the source of the cloudiness, which could indicate a serious problem.

The normal pH of urine ranges from 4.5 to 7.2 and averages about 6.0. The pH of urine is strongly affected by diet. High protein diets decrease the pH of urine while a mostly vegetable diet increases the pH. Consistently acidic urine can be a sign of metabolic acidosis, methanol poisoning or other medical disorders. In many cases, the pH of the urine of a person with a urinary tract infection is quite basic.

Specific gravity is the ratio of the weight of a volume of a substance compared to the weight of an equal volume of distilled water. (Water has a specific gravity of 1.000 g/cm³.) The specific gravity of urine depends upon the amount of solutes in solution and normally ranges from 1.005 to 1.025 g/cm³. The greater the concentration of solutes, the higher the specific gravity. In certain conditions, such as diabetes mellitus, specific gravity is high because of the high glucose content in the urine. Consistently dilute urine, with a specific gravity less than 1.005 g/cm³ is an indication of cardiovascular problems, diabetes insipidus or renal tube problems. A person who drinks a large volume of water each day most likely will produce a large volume of dilute (low specific gravity) urine.

Albumin or other proteins are normally absent from urine because the molecules are too large to be filtered out of the blood. High levels of protein in the urine are an indication of glomerular damage in the kidney. It may also be the result of excessive exercise, cold exposure or other acute abdominal diseases.

Urine normally contains such small amounts of sugar (glucose) that, clinically, glucose is considered to be absent in normal urine samples. The presence of glucose in significant amounts is call glucosuria, and the most common cause is certain diseases, such as diabetes mellitus. Other conditions such as pregnancy, excessive strain, renal tube damage or brain damage may also result in elevated glucose in the urine.

The kidney functions to help maintain a chemical balance (homeostasis) in the body. When the body’s metabolism becomes abnormal, many substances not normally found in the urine may appear in varying amounts while normal constituents may appear in abnormal amounts. Urinalysis is the analysis of the physical and chemical properties of urine and is a vital tool in diagnosing physiological conditions. It is, however, only a preliminary indication of possible problems and is always followed up with other appropriate tests for specific conditions.

Materials

Safety Precautions

Biuret test solution contains copper(II) sulfate and sodium hydroxide and is a corrosive liquid. It is moderately toxic by ingestion and is dangerous to skin and eyes. Benedict’s solution contains copper(II) sulfate, sodium citrate and calcium carbonate; it is moderately toxic by ingestion and a body tissue irritant. Avoid contact of all chemicals with eyes and skin. Wear chemical splash goggles and chemical-resistant gloves and apron. Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines.

Procedure

1. Five factors of urine are considered in this urinalysis simulation. Each of the five tests is described. Consider all five factors and complete all five tests on the simulated urine from individuals V, W, X, Y and Z.
2. Record the results of the tests on the Urinalysis Worksheet as each test is completed.
3. Answer the questions on the Urinalysis Worksheet when all of the data has been collected.

Specific Gravity Test

This will be done as a class demonstration. Shake each bottle of simulated urine thoroughly before performing this procedure. Fill the large test tube with approximately 40 mL of a simulated urine sample. Place the hydrometer in the urine sample in the test tube. The hydrometer will float in the urine and the specific gravity can be read on the hydrometer where the liquid is level with the hydrometer’s reading. Record the specific gravity for the sample. Save the simulated urine sample for further urine tests. Rinse and dry the test tube in between each successive urine sample.

Color Rating

Consider the color of the simulated urine sample. Describe the color as bright yellow, pale yellow, clear amber, cloudy or some other color descriptors.

pH Test

Use pH test paper to determine the pH of each simulated urine sample.

Sugar Test

Place 3 mL of simulated urine into a small test tube with 3 mL of Benedict’s test solution. Place the test tube in the hot water bath for about two minutes. Remove the test tube from the water bath after two minutes and note the final color of the solution in the test tube. The general color scheme is an indication of the relative amount of sugar in the urine:

Blue—Negative/no sugar
Greenish/Yellow—Small concentration of sugar
Orange/Yellow—Medium concentration of sugar
Red/Orange—Large concentration of sugar

Protein Test

Place 3 mL of the simulated urine sample into a small test tube. Transfer biuret test solution to the test sample one drop at a time. Swirl the test tube to mix the solution. Add a total of 15–20 drops. Note the initial color as soon as the biuret solution is added and then note the color again after a few seconds. A pinkish or lavender color indicates the presence of proteins in the urine.

Student Worksheet PDF

10200_Student1.pdf