Science Buddies: "Ask an Expert"

I'm doing a science fair project covering the Tyndall Effect and I'm curious to whether is it possible to find out the diameters of particles in colloidal solutions. I'm hoping to find a way to do this without buying an expensive tool. If there isn't a way to measure the diameters of the particles, is there something similar? I'm measuring colloidal silver, dilute milk, salt water, and a sugar-water solution. I do know that if any of these are true solutions that they will be < 1nm which is too small to measure at all.

Thanks,
Steven

Hello StevenW,

Yes, it is possible to measure particle sizes in suspensions and colloids. The following site lists several instrumental techniques for sizing particles in liquids.

http://www.micromeritics.com/Product-Sh ... -Size.aspx

Unfortunately all of the instruments are fairly expensive. Perhaps there is a nearby college lab with particle sizing equipment that would be willing to help.

I hope this helps. Please post again if you have more questions.

A. Norman

I've seen a few of those instruments on the site and I believe they are priced around $1000 so that is way out of price range. Is there a way to measure the particles using formulas or algorithms? If not, is there something similar I can measure that won't cost as much?

Hi StevenW,

Sorry, but I’m not aware of any substitutes or correlates for particle size measurements. Maybe one of the other contributors to this forum will have some ideas.

How does particle size measurement fit into your project plans? Is there a way to approach your project without the particle size measurements?

I hope this helps. Please post again if you have more questions.

A. Norman

Thanks for the information Norman.

I was planning to use the specific particle sizes as a dependent variable rather than just saying "this colloidal solution consists of particle sizes ranging from 1 nm - 1000 nm in diameter". I guess I wanted to go more in-depth with the project, however measuring the particles seems to be unattainable at the moment.

The only other dependent variable I have is stating whether the liquid is colloidal or not and that sounds pretty plain and vague. I'm honestly not sure of any other dependent variable I can measure in this experiment.

Steven W.

Hi StevenW,

There is a project on this site that you might be able to modify to fit with your interests. The project is described here:

https://www.sciencebuddies.org/science- ... ml#summary

In this project you build a light meter and use it to measure the intensity scattered light passing through colloids and suspensions. Part of the project is an investigation of the particle concentration effect on intensity of scattered light. You might consider testing diluted samples of the solutions you mentioned previously to observe effects on light intensity.

I hope this helps. Please post again if you have more questions.

A. Norman