What chemical is used in the emulsion that precipitates globulins?

Trichloroacetic acid (TCA) is utilized in histopathology and laboratory practices for precipitating proteins, particularly globulins, from biological samples. The mechanism involves TCA denaturing proteins, which leads to their aggregation and subsequent precipitation. This property is particularly valuable for separating proteins from serum or other fluids for analyses, such as in immunological assays or protein quantification.

By lowering the pH and disrupting the protein structure, trichloroacetic acid effectively isolates globulins, allowing for further study or quantification. The choice of TCA is significant because it is potent enough to precipitate globulins selectively without affecting other cellular components adversely. This specificity makes it a standard reagent in various protein analysis protocols in histopathology and clinical laboratories, reaffirming its role as the correct answer.