Today I've decided to explore an iodine clock reaction that can be done at home with household materials
The general gist of this reaction is that two colorless
solutions are mixed and then after a certain period of time a sudden color change occurs
There's a lot of different variations and recipes for the iodine clock reactions,
but pretty much all of them use some form of iodine and starch
so today, we're going to be doing the vitamin C variant and everything that you need is shown here as
I said before the reaction is a mixture of two colorless solutions
And this means we're going to have to be making a Solution A and a Solution B
Solution A requires two 1000 milligram tablets of Vitamin C,
iodine tincture (tincture of iodine) , and distilled water
My Iodine solution was 5% so I use 25 milliliters, but if your solution is let's say 2%
you'll have to use 60 milliliters. If you can only find 500 milligram tablets of Vitamin C,
you can just use four of those instead of two, and
also try not to get the chewable tablets because that has a bunch of extra stuff in it.
For Solution B, I used 0.4 grams of cornstarch
150 milliliters of 3% hydrogen peroxide and distilled water
It's important to note that in both of these solutions
I use distilled water, and we shouldn't use tap water because this can interfere with some things
We start off by making Solution A and for this we need two 1000 milligram tablets of vitamin C
Using the back of a spoon I try to crush the tablets
You don't have to completely powderize the tablets, but you don't really want to have any chunks left over either
The crushed pills are transferred to a suitable container and here I used the beaker, but in theory you could use anything really.
On top of the powderized pills, I then poured in about 60 milliliters of distilled water
This mixture is then stirred for something like 30 seconds
What we're doing here is we're trying to dissolve the vitamin C from the tablets into the water
Most of the pill though is just filler and stuff that's not soluble in water,
so don't try to dissolve everything because it's not going to happen
After about 30 seconds of stirring, we're left with a solution that kind of looks like this
Like I said there's a lot of insoluble stuff in the pills
So to get rid of this we're going to have to filter it off
The filter system is very simple, and it's just a couple coffee filters in a dollar store funnel.
I dumped the mixture into the coffee filters and very quickly a relatively clear solution starts to come through
This is going to take a little bit of time so while it's filtering I'm going to move on to making Solution B
To make Solution B, we first have to measure out a little bit of cornstarch.
In the beginning of the video I said to use 0.4 grams,
but it really doesn't have to be accurate and you can just estimate based on how much you see here in the video.
On top of the cornstarch I poured in about three hundred and fifty milliliters of distilled water
Once the water is added, I try to mix up the cornstarch, but the solution remains pretty cloudy
To try to dissolve as much cornstarch as possible the solution is placed in a microwave and heat up until boiling
Although it's clearer than before, it's still a little too cloudy for my liking so I filter it through something like four coffee filters
The solution that makes it through is a lot clearer, and it has a lot less free-floating undissolved cornstarch in it
Once it's all filtered through I remove the funnel and I turn the flask so I can see the volume markings
What we do now is we add about 150 milliliters of 3% hydrogen peroxide
After the peroxide is added and the solution is mixed a little bit
We're done making Solution B and we can move back to making Solution A
For Solution A, the next thing that we need to do is add our iodine tincture to our vitamin C solution
The iodine tincture is very dark and strongly colored but when it's added to the vitamin C
you can see that the color starts to disappear
After everything's added and the mixture is swirled,
it should go back to being colorless. If this doesn't happen it means you didn't have enough vitamin C
The color of the tincture is due to the presence of iodine or I2
but when it reacts with vitamin C, it's converted to iodide or I- which is colorless
To finish Solution A, we just top things off to about 500 milliliters
Solutions A and B are now complete, so we're done with our preparation and we can move on to the fun part
To test things out, we add roughly an equal amount of Solutions A and B to a beaker and then mix it up.
A sudden color change should occur, but this might actually take a little bit of time, so while we're waiting for things to change
I'm going to quickly talk about what's happening here in
Solution A we effectively have a mixture of vitamin C and colorless I- ions and
in Solution B we have hydrogen peroxide and starch
When Solutions A and B are mixed they actually start reacting together
but it's not just one reaction that's occurring it's two reactions
These two reactions are competing and they kind of push each other back and forth
The hydrogen peroxide wants to oxidize the I- back to colored I2
but the ascorbic acid
wants to reduce it from I2 back to I-
This reaction occurs really quickly and the I2 doesn't exist for very long and it's extremely transient
Eventually though the vitamin C is consumed because we've included an excess of hydrogen peroxide,
so I2 starts to accumulate
The I2 then very quickly
complexes with I- to form triiodide complex and this quickly complexes with starch
This all happens extremely quickly, and we're left with a nice blue complex of triiodide and starch
The concentration of each of the reactants and the temperature of the reaction mixture
will determine how long it takes for the color change to occur
The color change will occur quicker if we increase the concentration
of either the I- or the hydrogen peroxide and the color change will take longer if we increase the concentration of Vitamin C.
On top of concentrations,
we can alter temperature, so if we increase the temperature the color change will occur much quicker,
and if we decrease the temperature it will take longer
At the concentration and temperature that I did for this previous
demonstration it took about a minute to change but for me this was a bit too long,
so to speed things up I heated up my Solutions A and B in the microwave
After I heated them up they were around 50 °C and instead of taking something like a minute it took something around 10 to 20 seconds
Here we just have an example where Solution A is already in a beaker and I add Solution B
but we mix it the whole time
When the solution is being constantly stirred the color change occurs much more uniformly throughout the whole thing
We can also do the classic
demonstration where the solutions are mixed back and forth and then we slowly pour the solution from one into the other
When we do this the color should in theory change at the exact same time throughout all of the liquid.
Here it kind of looks like it wasn't all at the same time, but it still is pretty close
So here's a demonstration that I kind of thought might be cool where it looks like we make some instant coke
So just like all of the other demonstrations. We pour Solution A or B in and then we follow it with the other Solution
Pouring one solution into the other actually mixes things pretty well, but just to make sure that everything was thoroughly mixed
I shook it around a little
The color change occurs pretty quickly after I place the coke bottle back down
Some of you might be wondering why I have my phone with the timer running in the background
nd this is actually because I don't want people to claim that this is fake or something
I wait a few minutes, and then I place a glass on the side, and I pour out our freshly synthesized coke
The color is actually surprisingly
close to that of actual coke you know except for the purple cloud that comes off when I pour it into the glass
What's interesting is this is from another run, and I didn't wait long enough before pouring the solution, and you can actually see it's green
you have to actually wait a little bit for the peroxide to convert more I- to I2
which has a slight brown color in water
So for now, that's all I really have to say about this method for the iodine clock reaction.
I really want to do this method because it's very easily done at home
But I don't think the color change is as fast and instantaneous as some of the other methods
I've also decided to revisit and redo my previous iodine clock reaction video, and I've already filmed that and that should be up eventually
I haven't posted a video in a while, and it's not because I'm slacking,
it's because I've kind of gone on a rampage and filmed a bunch
So as usual a big, thanks goes out to all of my supporters on Patreon,
but I have to give a very special thanks to everyone who donated five dollars or more
Like I said in a previous video I kind of have too many $5 supporters to realistically read out each of your names
But just know that I still love you all