Synthetic or artificial urine is a laboratory-prepared solution that mimics the chemical composition of real human urine. It is commonly used for a variety of purposes, including medical testing, drug testing, calibrating equipment, and research. The composition of synthetic urine can vary depending on its intended use, but it typically includes the following components:

1. Water: The base of synthetic urine is purified water, making up the majority of the solution.

2. Urea: Urea is a key component of real urine, and it is included in synthetic urine to replicate its chemical properties.

3. Creatinine: Creatinine is another important component found in real urine, and it is added to synthetic urine to match the levels found in human urine.

4. Uric Acid: Uric acid is present in natural urine and is included in synthetic urine to provide a more accurate representation.

5. Ammonium Chloride: Ammonium chloride is sometimes added to synthetic urine to mimic the slightly acidic pH of real urine.

6. Sodium Chloride: Common table salt (sodium chloride) is included to ensure the synthetic urine has the right salinity.

7. Phosphate: Phosphates can be added to maintain the appropriate pH level and provide buffering capacity.

8. Creatinine: Creatinine is an organic compound that is a metabolic waste product excreted in urine. It is often included in synthetic urine to match the levels found in real urine.

9. Urobilin: Urobilin is a component responsible for the yellow color of urine. Synthetic urine may contain yellow dyes to achieve the appropriate color.

10. Other trace components: Depending on the specific use case, synthetic urine may contain other minor components to mimic the natural variations found in real human urine.

It's important to note that there are commercially available synthetic urine products designed for various applications, including calibration, quality control, and drug testing. These products are formulated to closely mimic the characteristics of real human urine, including color, smell, and chemical composition. However, the exact composition of synthetic urine can vary between brands and products.