Which test is recognized as the earliest chemical test for the presence of glucose in urine?

The copper reduction test is considered the earliest chemical test for the presence of glucose in urine. This test is based on the principle that glucose can reduce copper ions from cupric to cuprous state, which leads to the formation of a colored precipitate or change in color in the reaction medium. This property of glucose was first utilized in the early 20th century to detect the presence of reducing substances in urine, making it a fundamental method for identifying glycosuria (glucose in urine).

This test laid the groundwork for understanding diabetes and certain metabolic disorders, which can lead to the presence of glucose in the urine when blood sugar levels are elevated beyond the renal threshold. Although other methods, such as colorimetric glucose tests and urine dipstick tests, have become more common later on due to their ease of use and quicker results, the copper reduction test retains historical significance as the pioneering approach to glucose detection in urine analysis.