Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Iwonda on 28/03/2022 05:21:58
-
I was doing some acid testing on a strange piece of pyrite, and I noticed that a lot of bubbles were sitting in the bottom of the solution. I put a fragment in some acid and watched it under a microscope, on one side a bubble would come out, rise to the top and pop and on the other side a bubble would form and drop to the bottom. Just a bit curious as to what element would produce a heavy gas bubble like this.
-
I don't think there are any gases that are more dense than water under standard conditions, so it sounds like something else is going on.
-
Our normal image of a bubble comes about because of the difference in refractive index between the gas (η=1.00000x) and water (η=1.33).
A clear liquid with a refractive index much higher than water (eg η=1.6) would give a similar amount reflection as a gas bubble.
What sort of acid?
Was it Iron Pyrite FeS2?
https://en.wikipedia.org/wiki/Pyrite
Normally, when a solid is dissolved by an acid, whatever doesn't bubble off just diffuses outward as ions, rather than concentrate in dense immiscible droplets...
But there are many people on this forum who know chemistry better than I!
-
The most likely explanation is that a falling bubble has a small chip of pyrites or something stuck to it, weighing it down.
-
What sort of acid?
The acid used was muriatic acid and stone is pyrite. I have photos of some of the acid solutions with scores of the bubbles showing. I'll see if I can dig up a few and post them.
-
I was doing some acid testing on a strange piece of pyrite, and I noticed that a lot of bubbles were sitting in the bottom of the solution. I put a fragment in some acid and watched it under a microscope, on one side a bubble would come out, rise to the top and pop and on the other side a bubble would form and drop to the bottom. Just a bit curious as to what element would produce a heavy gas bubble like this.
Can you show a picture, or better yet, a video?
A picture is worth a thousand words.
-
The most likely explanation is that a falling bubble has a small chip of pyrites or something stuck to it, weighing it down.
Agreed. This was my first thought as well. I have seen this kind of thing before.
If there is a small grain of pyrite it will sink to the bottom initially. Then, as the grain reacts with the acid and releases gas (presumably carbonate or sulfide contaminants... I don't think FeS2 should react vigorously with HCl...), it can build up a bubbles of gas that stick to the grain. Once there is enough gas stuck to the grain, it will start to float up, and may make it all the way to the surface, where it releases some or all of the bubbles and falls back down, carrying any remaining bubbles with it.
-
I did a number of acid test, the end results were almost always something different than the last, the one thing that was consistent were the bubbles and that's why I was curious as to what element might be producing the bubbles. No one can say why, but this pyrite has a thing for sphere shapes. Here are some photos of the bubbles in question. [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ] [ Invalid Attachment ]
-
Separation of sulphide ores by attaching them to bubbles has a long history:
https://en.wikipedia.org/wiki/Froth_flotation#Mineral_Processing
-
Separation of sulphide ores by attaching them to bubbles has a long history
Hmm, can froth flotation be performed on a microscope slide using just a couple drops of acid?
-
on the other side a bubble would form and drop to the bottom.
When boiling water using gas stove or induction heater, usually we find bubbles form from the bottom of the container, which is the hottest part in the system. Did you see the bubbles form somewhere above the bottom before they fall down to the bottom?
-
Did you see the bubbles form somewhere above the bottom before they fall down to the bottom?
I had put a small fragment of pyrite (about 3mm) in a small plastic container and put enough acid to cover it, as I watched it under the microscope, I could see bubbles form at the top of the fragment and slowly drift to the bottom of the solution. In some of the test I would crush the fragments and place a gram or so on a slide and put a couple drops of acid and when I looked at it, there would be several bubbles just sitting on the bottom. I do have a video of the fragment test, but I think the file is too large to upload on here. I was curious about this because, I bought a piece of normal pyrite and when I do the same test I get a foamy blob like substance and not bubbles like this.
-
I do have a video of the fragment test, but I think the file is too large to upload on here.
You can upload it to Youtube and just post the link here.
-
You can upload it to Youtube and just post the link here.
Okay, I uploaded the video to YouTube but the link for some reason isn't working for me, so just go to the YouTube site and in the search box type: Strange bubbles or fragment to bubbles and that should bring up the videos.
-
I found your videos.
Let me share them here.
Bubbles on the move.
Fragment to bubble.
Strange bubble.
Other videos pop up first when I searched. Your videos came out after I added "pyrite" into the search words.
-
There are all sorts of things that can cause bubbles to move:
- Thermal gradients (eg heating by the microscope lamp, or the chemical reaction)
- Concentration gradients due to the chemical reaction
These bubbles are quite black, so they have a significant component that is not gas.
-
These bubbles are quite black, so they have a significant component that is not gas[/qu
The bubbles look black when they are lit from below and when lit from above they look transparent and sometimes white. This pyrite is very strange, it seems to have a thing for spheres, I have seen spherical structures grow out of the acid solution and there are even tiny spheres embedded in some of the pyrite crystal, to date no can explain any of this. There are over 27 different elements detected in this pyrite, I was curious as to which one might be creating these heavy bubbles.