1800-2000-838

+91-120-4616500

Colloidal State

(1) The foundation of colloidal chemistry was laid down by an English scientist, Thomas Graham, in 1861. The credit for the various advances in this field goes to eminent scientists like Tyndall, Hardy, Zsigmondy, N.R. Dhar, S.S. Bhatnagar and others.

(2) Thomas Graham classified the soluble substances into two categories depending upon the rate of diffusion through animal and vegetable membranes or parchment paper.

(i) Crystalloids : They have higher rate of diffusion and diffused from parchment paper.

Examples : All organic acids, bases and salts and organic compounds such as sugar, urea etc.

(ii) Colloids (Greek word, kolla, meaning glue-like) : They have slower rate of diffusion and can not diffused from parchment paper.

Examples : Starch, gelatin, gums, silicic acid and hdemoglobin etc.

(3) The above classification was discarded i.e., the terms colloid does not apply to a particular class of substances but is a state of matter like solid, liquid and gas. Any substance can be brought into colloidal state.

(4) The colloidal state depends on the particle size. If is regarded as intermediate state between true solution and suspension.

Table: Features of the three types of solutions

Property Suspension Colloid solution True solution
Nature Heterogeneous Heterogeneous Homogeneous
Particle size > 100 nm 1 nm – 100 nm < 1 nm

Separation by

(i) Ordinary filtration

(ii) Ultra- filtration

 

Possible

Possible

 

Not possible

Possible

 

Not possible

Not possible

Settling of particles Settle under gravity Settle only on centrifugation Do not settle
Appearance Opaque Generally transparent Transparent
Tyndall effect Shows Shows Does not show
Diffusion of particles Does not diffuse Diffuses slowly Diffuses rapidly
Brownian movement May show Shows Negligible

 

NEET & AIIMS Exam Sample Papers

AIIMS SAMPLE PAPERS
Solved Sample Paper 1 Solved Sample Paper 2 Solved Sample Paper 3
Solved Sample Paper 4 Solved Sample Paper 5 Solved Sample Paper 6
View More
 
NEET SAMPLE PAPERS
Solved Sample Paper 1 Solved Sample Paper 2 Solved Sample Paper 3
Solved Sample Paper 4 Solved Sample Paper 5 Solved Sample Paper 6
View More

Get practice papers FREE

BOOK A FREE TRIAL
Copyright © 2010-2018 www.emedicalprep.com. All rights reserved.
Skip to toolbar