The gold number is a measure of the protective power of a lyophilic colloid. It is defined as the minimum amount of a lyophilic colloid (in milligrams) that is required to prevent the coagulation of 10 mL of a gold solution by the addition of 1 mL of a 10% NaCl solution.
A lower gold number indicates a higher protective power of the lyophilic colloid, meaning it takes a smaller amount of the colloid to prevent coagulation. Conversely, a higher gold number indicates a lower protective power.
Let's analyze the given gold number ranges:
A: 0.005–0.01: This range indicates a very low gold number, meaning the colloid has high protective power.
B: 0.15–0.25: This range indicates a relatively low gold number, but higher than A.
C: 0.04–1.0: This range is broader and includes values higher than A and B.
D: 15–25: This range indicates a very high gold number, meaning the colloid has low protective power.
The question is asking for the lyophilic colloid with the highest protective power, which corresponds to the lowest gold number. Therefore, the colloid with the range 0.005-0.01 has the highest protective power.
