`10^(-4)g` of gelatian is required to be added to `100cm^(23)` of a standard gold sol to just prevent its coagulation by the addition of `1cm^(3)` of `10%NaCl` solution to it. Hence the gold number of gelatain is

Options

A. `10`
B. `1.0`
C. `1`
D. `0.01`

Answer

D

Explanation

Gold number is the number of milligrams of a lyophilic colloid that will just prevent the precipitation of `10mL` of a gold sol on the addition of `1mL` of `10%` sodium chloride solution.
`100cm^(3)` (0r `100mL`) of gold sol required `10^(-4)g` of gelatin. Thus, the amount of gelating needed to protect `10mL` (or `10cm^(3)`) of gold sol will be
`(10^(-4)xx10)/(100)=10^(-5)g`
`=(10^(-5)g)((1000mg)/(1g))`
`=10^(-2)mg`