Fluorescein | the experiment

Well, you see, making fluorescein isn’t as easy as snapping your fingers and voilà! It requires a bit of scientific know-how and experimentation. In this particular experiment, I attempted to make fluorescein (with @jasmin-k). Unfortunately, the first try didn’t go as planned due to a shortage of equipment and having to make do with whatever we had at hand. But hey, that’s the beauty of science—it’s all about learning and trying again. Now, let me break it down for you. To make fluorescein, we need a few key ingredients that are always the same, regardless of whether we succeed or not:

• Phthalic anhydride
• Resorcinol
• ZnCl2

In the first step, I mixed ten millimoles of phthalic anhydride and twenty millimoles of resorcinol in a two neck flask. I also added a magnetic stirrer to ensure everything blends together nicely. Now, the crucial part is achieving a uniform mixture, and for that, we need to heat things up in an oil bath at a temperature of 180 degrees Celsius. Unfortunately, I didn’t have silicone oil, which is ideal for reaching that temperature. So, we improvised and thought using a sand bath might do the trick. It wasn’t perfect, though, as the magnetic stirrer didn’t work properly, and the mixing wasn’t as uniform as we hoped. But hey, I’m not one to give up easily!

Once the substances were heated and combined, it was time to introduce twenty millimoles of zinc chloride into the mix, adding it slowly through one of the flask necks. Now, we let the substances mingle at the same temperature for a good 45 to 90 minutes. Patience is key!

When they turned a deep red colour, I switched off the heater and let the temperature drop to ninety degrees Celsius. At this point, I added twenty millilitres of water and one millilitre of concentrated HCl. Now, here’s an important note: toxic vapours are produced during this process, so it’s crucial to carry it out in a well-ventilated space or under a hood. Safety first, always!

To ensure complete dissolution of the substances, I placed the solution back on the heater. Once that was done, I filtered the solution, washed it with water, and finally, dried it in an oven.

Now, here’s where things took a turn. The first attempt didn’t yield any precipitate, which meant starting over from scratch. But I didn’t let that dampen my spirits.

For the second try, I used an oil bath with silicone oil, which provided better results. After going through all the previous steps, it was time for the purification stage.

In this stage, we have to make a solution containing NaOH and HCl.

After adding them (dissolved in NaOH solution and precipitating with dilute HCl), filter the solution several times and wash it with water. Then, dry it in an oven at one hundred degrees Celsius.

And there you have it (I will show the results in the post I’m going to make in the future. So, stay tuned)! Fluorescein is ready to shine its vibrant colours. Science can be a bumpy road, but with determination and a bit of improvisation, we can make amazing discoveries. Allons-y!

— Deducter