Which substance can be used for chemical preservation of urine samples?

Formalin is commonly used for the chemical preservation of urine samples due to its ability to inactivate bacteria, fungi, and viruses, thus preventing decomposition and preserving the cellular and chemical constituents in the urine. Additionally, it helps to stabilize various biochemical components, which is crucial for performing accurate laboratory analyses later.

On the other hand, substances like ethyl alcohol, acetic acid, and hydrochloric acid may not be suitable for urine sample preservation. Ethyl alcohol can lead to unwanted reactions and can alter the urine's composition, potentially affecting test results. Acetic acid might cause changes in pH and disrupt the biochemical integrity of the sample. Hydrochloric acid, being a strong acid, can severely alter the chemical nature of urine and damage any cellular components that might be needed for analysis. Therefore, formalin stands out as the more appropriate choice for preserving urine samples for laboratory testing.