Chemistry

This is not some sort of fancy new development, but it's such a classical experiment that it's always worth sharing IMO. Plus it's fun.

When you initially mix both solutions, nothing seems to happen. But once you wait a wee bit, the colour suddenly changes, from transparent to a dark blue.

There are a bunch of variations of this reaction, but they all boil down to the same things:

• iodide - at the start of the reaction, it'll flip back and forth between iodide (I⁻) and triiodide ([I₃]⁻)
• starch - it forms a complex with triiodide, with the dark blue colour you see in the video. But only with triiodide; iodide is left alone. So it's effectively an indicator for the triiodide here.
• some reducing agent - NileRed used vitamin C (aka ascorbic acid; C₆H₈O₆), but it could be something like thiosulphate (S₂O₃²⁻) instead. The job of the reducing agent is to oxidise the triiodide back to iodide.
• some oxidiser - here it's the hydrogen peroxide (H₂O₂) but it could be something like chlorate (ClO₃⁻) instead. Its main job is to oxidise the iodide to triiodide. You need more than enough oxidiser to be able to fully oxidise the reducing agent, plus a leftover.

"Wait a minute, why are there a reducing agent and an oxidiser, doing opposite things? They should cancel each other out!" - well, yes! However this does not happen instantaneously. And eventually the reducing agent will run dry (as long as there's enough oxidiser), the triiodide will pile up, react with the starch and you'll get the blue colour.

Here are simplified versions of the main reactions:

1. 3I⁻ + H₂O₂ → [I₃]⁻ + 2OH⁻
2. [I₃]⁻ + C₆H₈O₆ + 2H₂O → 3I⁻ + C₆H₆O₆ + 2H₃O⁺

(C₆H₆O₆ = dehydroascorbic acid) Eventually #2 stops happening because all vitamin C was consumed, so the triiodide piles up, reacts with the starch, and suddenly blue:

Dr Thomas de Prinse makes yttrium oxide doped with erbium and ytterbium.

Upconversion: Material absorbs two infrared photons, emits one visible photon.

A chemist told me rust does not spread. The top of my refrigerator gives me some doubt. It’s covered in these spots. The center of every spot is a small break in the paint, but the rust all around those spots is on top of the paint.

cross-posted from: https://lemmy.ca/post/39143995

The authors of the academic study, published in the Journal of the American Chemical Society on Thursday, had to get the smell from inside the sarcophagus without interfering with the mummy inside.

The researchers, from UCL and the University of Ljubljana in Slovenia, did so by inserting a tiny tube so they were able measure the scent without taking any physical samples.

If you want to smell the smell too

They say recreating the composition of the smells chemically will allow others to experience a mummy's whiff - and help to tell when the bodies inside may be starting to rot.

"We want to share the experience we had smelling the mummified bodies, so we're reconstructing the smell to be presented in the Egyptian Museum in Cairo," Cecilia Bembibre, one of the researchers, told BBC Radio 4's Today programme.

It's not really "professional" but you can look at the process, see the results and come to your own conclusion about it's viability.

[Maurycyz] points out right up front: several of the reagents used are very corrosive and can produce toxic gasses. We weren’t sure if they were trying to dissuade us not to replicate it or encourage us to do so. The project in question is making strontium aluminate which, by the way, glows in the dark.

The material grows strongly for hours and, despite the dangers of making it, it doesn’t require anything very exotic. As [Maurycyz] points out, oxygen and aluminum are everywhere. Strontium sounds uncommon, but apparently, it is used in ceramics.

Scott usually focuses on spaceflight and aviation topics, but there is some nice chemistry overlap in this video.

Dr Thomas de Prinse undertakes the first two steps of his large-scale cubane synthesis in his shed.

Another fantastic video from the OG YouTube Chemist.

Dr Thomas de Prinse announces his intentions to repeat his cubane synthesis on a larger scale.

I put an aluminum wok lid in the dishwasher and it came out with black marks on it. I’ve also seen other aluminum cookware come out with some kind of white powder specs on it.

So apparently aluminum is dishwasher unsafe. But obviously it’s not the water that’s the problem. It must be the detergent. So the question is, what can a lazy motherfucker like myself do? Why don’t I see aluminum-safe dishwasher detergents on the shelf?

Possibly related: Bailey’s creme liquor turns black underneath an aluminum cap. Is that a chemical reaction or spoilage, or something else?

Thought u guys might find this useful

Consider watching this video with FreeTube, a nifty open-source program that lets you watch YouTube videos without Google spying on your viewing habits!

Combined with Libredirect, which automatically opens youtube links in Freetube, it becomes really slick and effortless to use.

I acquired a ~16 year old laptop. The mat black plastic top (back of the LCD) is sticky. At first I thought the previous owner had stickers on the back that were removed. But that seems like a bad theory now. I rubbed it with a cloth and denatured alcohol and it only got slightly less sticky, but black residue came off on my hands and the cloth. This is apparently not adhesive.. it’s the plastic itself.

What’s my best move? I don’t suppose I can do anything to re-polymerize it. I don’t care about cosmetics.. I just don’t want it to be sticky and marking anything that touches it. One temptation is to put plastic film on it, like cling wrap. But that could just make a bigger mess.

In the heart of World War II, as the Nazis took control of Copenhagen, a peculiar situation took place at the Institute of Theoretical Physics, led by physicist Niels Bohr. Two Nobel laureates Max von Laue and James Franck, fearing the confiscation of their gold Nobel Prize medals by the Nazis, had sent their medals to Bohr for safekeeping.

On the day the Nazis arrived in Copenhagen, Hungarian chemist Georgy de Hevesy, who was working in Bohr's lab, devised a plan to prevent the discovery of the medals. Initially considering burying the medals, they quickly dismissed the idea, fearing the thorough searches the Nazis would conduct. Instead, de Hevesy proposed a chemical solution — literally. Utilizing a mixture known as "aqua regia" (a blend of hydrochloric and nitric acids), he set about dissolving the gold medals. This concoction is one of the few substances capable of dissolving gold, a notably unreactive element. As the Nazis marched outside, de Hevesy dissolved the precious medals, reducing them to a colorless solution that eventually turned bright orange. The liquid containing the dissolved gold was then placed on a high shelf in the laboratory, where it remained unnoticed throughout the Nazi occupation​.

Post World War II, upon returning to the laboratory after V-E Day, de Hevesy found the beaker undisturbed on the shelf. The gold was recovered from the solution and returned to the Nobel Prize committee, who then reminted the medals and presented them back to Laue and Franck in a ceremony in 1952.

Source: Fermat’s Library via LinkedIn

Periodic Videos have updated their scandium video.

Another great video from NurdRage. One of the most detailed and methodical YouTube chemists.