How did Justus von Liebig develop a chemical test for urea in urine?

Justus von Liebig did not develop a specific chemical test for urea in the early stages of his career; rather, he and his collaborator Friedrich Wöhler conducted foundational research between 1837 and 1838 to identify and classify the constituents and degradation products of urine, including urea (carbamide), uric acid, and allantoin.1

It was not until 1852 that Liebig provided physicians with simple chemical procedures that allowed them to quantitatively determine the amount of urea present in urine. This work was part of his broader efforts to apply organic chemistry to physiology and pathology, which helped provide medical professionals with new insights into the pathology of various kidney and urinary bladder diseases.12