Question
Question: On addition of one ml solution of 
to 10 ml gold sol in the presence of 0.25 gm of starch, the coagulation is just prevented. Starch has the following gold number.
A
0.025
B
0.25
C
0.5
D
250
Answer
250
Explanation
Solution
Sol By definition gold number of starch is the amount of starch in mg added to 10 ml standard gold sol which prevents the coagulation of gold on adding 1 ml of 10% NaCl solution. So the amount of starch is 0.25g = 250 mg. Hence gold number is 250.