Question

Gold number of hemoglobin is 0.03. Hence 100ml of gold sol will require hemoglobin so that gold is not coagulated by 10ml of 10% NaCl solution
(A) 0.03 mg
(B) 30 mg
(C) 0.30 mg
(D) 3 mg

Answer 1

The Gold Number is the base weight (in milligrams) of a defensive colloid needed to forestall the coagulation of 10 ml of a standard hydro gold sol when 1 ml of a 10% sodium chloride arrangement is added to it. It was first utilized by Richard Adolf Zsigmondy.

Complete step-by-step answer: Gold number $= 0.03$
Gold sol volume $= 100ml$
Let the measure of hemoglobin required is $x{\text{ }}mg$
Since the gold number is the sum in milligrams needed to forestall the coagulation of 10 ml of gold sold$by{\text{ }}1{\text{ }}ml{\text{ }}of{\text{ }}10\% {\text{ }}NaCl$
$\Rightarrow \frac{x}{{100}} \times 10 = gold number$
$\therefore x = 0.30mg$
Zsigmondy presented a term called the gold number to portray the defensive intensity of various colloids. This is characterized as, "weight of the dried defensive specialist in milligrams, which when added to 10 ml of a standard gold sol (0.0053 to 0.0058%) is only adequate to forestall a shading change from red to blue on the option of 1 ml of 10 % sodium chloride arrangement, is equivalent to the gold number of that defensive colloid." Subsequently, the more modest is the gold number, the higher is the defensive activity of the defensive specialist.
Table: Gold numbers of some hydrophilic substances

Hydrophilic substance	Gold number	Hydrophilic substance	Gold number
Gelatin	0.005 - 0.01	Sodium oleate	0.4 – 1.0
Sodium caseinate	0.01	Gum tragacanth	2
Hemoglobin	0.03 – 0.07	Potato starch	25
Gum arabic	0.15 – 0.25

Hence the correct answer is an option (C).

Note: An electrical twofold layer is regularly present on the gold sol particles, bringing about electrostatic repugnance between the particles. The sodium chloride particles disturb this electrical twofold layer, making coagulation happen.