Cool Blue Light of Luminol

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midkxo
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Cool Blue Light of Luminol

Post by midkxo »

Hi I would like to ask a few questions about the experiment.
So I'm going to remake the experiment by focusing on the different concentration of catalyst instead of the temperature. There are a few issues that I'm confused about.
1. Why do we need to wait 20 seconds before taking the photos?
2. Why do we need to record the time intervals between each photo taken?
3. What does it mean to "Pick five pictures of the blue light in the cups that form a series from the brightest (5) to the dimmest that is still visible (1). Which reaction produced the brightest light?
Make a figure based on these five. This will be your standard for assigning a brightness level to each cup."?
4. Do I need to record time if I want to compare the effect of concentration of catalyst (my own project)?
5. Can I take the pictures of just one cup for each photo? So every picture will have one cup only.

Thank you!!!
norman40
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Re: Cool Blue Light of Luminol

Post by norman40 »

Hello midkxo,

I’m assuming that you’re working on the project described here:

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

This project involves measuring the rate of the luminol reaction. Changes in the brightness of light produced by the reaction are used to indicate how fast and how much of the luminol reacts over time.

Regarding your questions:

1. I did not find any instruction in the procedure about waiting 20 seconds before taking photos. The caption in Figure 3 notes that the example photo was taken 20 seconds after starting the reaction.

2. The object of the experiment is to follow how fast the reaction proceeds under different conditions. To do this, you measure the light brightness emitted over time. Thus you must record the times at which your photos are made.

3. You make a judgement of which photos show the brightest and dimmest light. Assign the number 5 to the brightest and assign the number 1 to the dimmest. Use you judgement to assign the numbers 2, 3 and 4 to photos showing increasing levels of brightness between the dimmest and brightest. This is your measurement scale. This is easier to do with image analysis software such as Photoshop, as suggested in the project procedure.

4. Yes, you should record the times for the experiment you described. My suggestion is to have two catalyst concentrations. Run the experiment as described in the procedure but substitute the two catalyst concentrations for the two temperatures.

5. If you follow my suggestion from above, it would be more efficient (fewer photos) to have both cups (one with each catalyst concentration) in the same photo. This procedure also assures the same camera settings for both catalysts.

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

A. Norman
midkxo
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Re: Cool Blue Light of Luminol

Post by midkxo »

So what should I do with the image analysis software? Because I want to use ImageJ to analyse the picture. Can I measure the intensity of specific pixels using the image analysis software and use that as the measurement scale? What is the measurement scale implying? I still don't get it.
norman40
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Re: Cool Blue Light of Luminol

Post by norman40 »

Hi midkxo,

The project procedure includes directions for making a brightness scale based on your judgement. Luminol emits light in this reaction. And more light (brighter) indicates that more luminol is reacting. Thus the brightness scale is a way to indicate the amount of luminol that is reacting.

An alternative way of assigning brightness values is to use image analysis software to find the average brightness (or gray value) of the photos you take of the reaction cups. You’ll need to select the areas of the photos that you want to measure. Then use the histogram feature of the software to display the average gray value.

Detailed instructions for using ImageJ to measure image brightness are available at the following link:

https://www.sciencebuddies.org/science- ... #procedure

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

A. Norman
bvallejo315
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Re: Cool Blue Light of Luminol

Post by bvallejo315 »

Hello,
Do you know the chemical equation? I am unable to find the products.
midkxo
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Re: Cool Blue Light of Luminol

Post by midkxo »

I still dont get what the exposure means. So does exposure means that I need to take multiple shots in an interval of time for one cup (one concentration) and then analyze the brightness using imageJ and then take the average of the brightness for one concentration? Then what is the scale for?
norman40
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Re: Cool Blue Light of Luminol

Post by norman40 »

Hi midkxo,

The basic idea in this experiment is to track the change in light emitted from the luminol reaction over time. To do this, you take a photo of a reaction cup at different times. The brightness of the photos indicates the amount of light emitted by the reaction. You can analyze the brightness of the photos with ImageJ or you can use a subjective scale as described in the project procedure. You don’t need the subjective scale if you use ImageJ for analyzing brightness.

The term “exposure” refers to camera settings used for the reaction cup photos. The project procedure instructs you to make a series of test photos with different exposure times (set the shutter speed to 5-, 10- and 15-sec) to see which time produces a clear image of the reaction cups. Once you’ve established a good exposure setting, you must keep the camera settings constant during the experiment. If you change the camera settings, you would observe a brightness change that is not due to the reaction.

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

A. Norman
midkxo
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Re: Cool Blue Light of Luminol

Post by midkxo »

Hi,
Thanks for explaining it to me. Oh by the way I thought that I can actually video-record the reaction instead of taking pictures in different times. Do you think it's a good way to do it? So by recording it I won't need to record the time and take pictures of the reactions everytime. What do you think?
norman40
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Re: Cool Blue Light of Luminol

Post by norman40 »

Hi midkxo,

You might be able to use a video recording instead of photographs. Because of the low level of light emitted from the reaction you’ll need a video camera that’s very light-sensitive. And you’ll need to work out a way to analyze the brightness of the reaction cups at different times in the video. I think it may be easier to do the experiment with a still camera as described in the project procedure.

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

A. Norman
midkxo
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Re: Cool Blue Light of Luminol

Post by midkxo »

Hi Norman,
I video-recorded the reaction with my camera and I screenshotted the video in an interval time of 2 seconds to get the pictures and then analyze it. So when I'm trying to analyze it using image J, I found out that using the website you gave me (the steps) is to analyze the calibration photo which the brightness of it is scattered. However, my photo (the screenshots) is only bright on the liquid and not on the background (background is pitch black) so do I need to select the pixels (focus it on just the liquid part) or just follow the steps you gave me? if I select the pixels then I'm gonna select the same amount of pixels on other picture I screenshotted. How about that? Thank you
norman40
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Re: Cool Blue Light of Luminol

Post by norman40 »

Hi midkxo,

The ImageJ instructions that I posted earlier assume that the images to be analyzed have consistent brightness over the image area. These instructions include a camera calibration that you don’t need for your experiment. Step #8 describes how to make an brightness measurement.

You noted that your images have a wide brightness range. And ImageJ will report an average brightness value that should vary with the luminol reaction time.

You may get better results by selecting and analyzing the part of the image showing the reaction cup as you suggest. You’ll need to work out a way to select the same area of each the images from your time interval sequence. Otherwise brightness variation from selection of different image areas might interfere with observing the brightness changes due to the reaction.

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

A. Norman
midkxo
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Re: Cool Blue Light of Luminol

Post by midkxo »

Hi Norman,
What do you mean by "you’ll need to work out a way to select the same area of each the images from your time interval sequence"? Do I really need to select the SAME areas of each image or just select the area that shows the brightness in each image (this means that I'm just gonna select the area that I THINK shows the brightness so there might be slightly different locations of the brightness due to the beaker being moved in every reaction)? But I'm still gonna use the same amount of pixels for every reaction, it's just the area that's different. Do you think this works or I just use the histogram of average brightness of the whole picture? Also, the only thing that we need to take note is only the average of the brightness right? We don't need the standard deviation and etc of each image right? And what units are the average brightness in?
Thank you!
norman40
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Re: Cool Blue Light of Luminol

Post by norman40 »

Hi midkxo,

My suggestion is that you analyze the same location and area of each of your images. If you select part of an image for analysis, you should select the same number of pixels in the same location on all other images.

The standard deviation reported for the histogram by ImageJ indicates the variability of the brightness within the selected image area. I don’t think you need the standard deviation for your experiment.

I don’t know the units for the values reported by ImageJ.

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

A. Norman
midkxo
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Occupation: Student

Re: Cool Blue Light of Luminol

Post by midkxo »

Hi Norman,
I still haven't figured out which method that I need to use. Why do we have to select the same pixels on the same locations on every picture? Because at 2 seconds, the volume isn't as much as at 10 seconds (as I pour it). And if I use the same size of selection, then at 2 seconds there will be just a little bit of solution and the rest is the background (not a total darkness due to the light emitted by the luminol). Is this okay?
If I use the same location or area of selection on every picture, then it would not be reliable because i moved the beaker (beaker's position on every video is not the same) so the selection will not be concentrated on the bright part.
What do you think about this?
norman40
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Re: Cool Blue Light of Luminol

Post by norman40 »

Hi midkxo,

The brightness values you measure may vary due to the location and area of the image. To try to avoid this, you should analyze the same location and pixel area of your images. Ideally the area of the image you analyze would include only the reaction beaker.

For the first situation you described (low volume in the beaker after 2 sec), why not start analyzing images after the beaker is filled and the reaction has started? I don’t think this reaction is so fast that you’ll lose any information by waiting for 10 sec before analyzing the first image.

For the other situation (beaker position not the same), you could move the image analysis area to cover the beaker’s new position. But the pixel count (selection area) should be kept constant. By the way, would it be possible to mark the beaker position so that you put it in the same spot for each reaction trial? If so, that would be another option for making the image analysis more consistent.

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

A. Norman
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