Question

Gold number of haemoglobin is 0.03. Hence 100 ml of gold sol will require haemoglobin in what quantity so that gold is not coagulated by 10ml 10% NaCl solution

• A. 0.03 mg
• B. 0.003 mg
• C. 0.3 mg
• D. 300 mg

Answer 1

The correct option is C

0.3 mg

Gold number is the minimum amount of protective colloid in milligrams which prevents a color change from red to violet of 10ml gold sol by the addition of 1 ml of 10%NaCl solution.

10 ml of sol needs 0.03 mg of haemoglobin (as per gold no.) therefore 100 ml of sol would need =100 ml $\times$ 0.03 mg/10ml
=0.30 mg haemoglobin.