Basically one can use phones as Colourimeter by Beer’s Law which is an equation that relates the attenuation of light to properties of a material. The law states the concentration of a chemical is directly proportional to the absorbance of a solution.
- Absorbance = - log ( Intensity / Intensity of 0 molar solution. )
We first get a number of data points of known molarity and it’s obserbance ( the more the data the result will be ) Then we plot concentration as a function of Absorbance and derive the equation of best fit line and use that equation to find unknown concentrations.
- Absorbance = m( concentration) + b
- Concentration = (Absorbance - b) / m
But how do we have to proceed on mobile …consider everyone is going to start it for the first time, so which apps to use ? how to use that app ? What’s all things need to be done ?
In earlier discussions in the Maker Lab, we had come to learn about a very simple colorimeter application for a mobile phone, that could be useful for solving a very serious current problem. This has already been researched at MIT, Massachusetts.
It analyses the color of blood samples to determine whether the blood has been infected with malaria. This helps decide very quickly whether to administer the medication for falcipuram, which is both on the expensive side and also debilitating. Worse, it does not help in treating the milder form of malaria.
Either the prior researched hydrogel forming compound can be used, or further work can be done to identify other compounds that might be even easier to source in India, in order to popularise this method of detection.
But instead of of going through all that research wouldn’t the method from video below give the required results?
@pratittodkar
Please find this apk file of colorimeter app, it gives RGB values of any given spot using mobile camera. Can this be used to measure light intensity?
https://m.apkshub.com/app/com.colorimeter
Ya that one is better than the one I told. It will work.
It is showing RGB values of the image in the center of camera. Don’t choose the picker option instead go to the scan and see. That’s precisely what we will need for the colorimeter.
picker gives us option to take picture.
Scan is just to scan the sample without taking picture.
We need to take picture of the sample…
But picker dosen’t gives live results and we do not want to be moving any part of the setup so as little touching as possible should be there and for that scan is better. We can get the photo by taking a pic of the screen with a different mobile if we want.
I was wondering the same, easy way out is to just take a screenshot if photo option is not available…
Ya but for that also we will have to touch the setup. Instead as I told why not take photos with a different mobile or use a selfie stick for it.
Can you please explain from start how to use the app? It will be great as many cubists wanna use this mobile calorimeter. Please tell us from start with pictures so that understanding could be easy.
- Take a printout on a paper of the particular color that you solution is going to absorb.
- Place that printout behind the solution.
- Make a stand as shown in the above video.
- Take the RGB reading for the medium with zero concentration of absorbing compound.
- Now take the RGB readings for at least three different molarities of the absorbing compound.
- The I values will be the sum of RGB values that change. Ignore minute fluctuations
- After that use the formula
A=-log(I/I (with zero concentration))
to get absorbance values. - Plot the graph of Absorbance vs Concentration and find the best fit line.
- Get the equation for the line.
- Find the unknown concentration using the slope-intercept equation of that particular line.
If you are having problem taking RGB readings then refer to @jaikishan