Before N₂O₅: Making Liquid Nitrogen Dioxide

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Before N₂O₅: Making Liquid Nitrogen Dioxide

ChemicalForce 21.04.2026 29 460 просмотров 1 896 лайков

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Hey guys! Before synthesizing nitric acid anhydride, I’ll show you some chemistry of liquid nitrogen dioxide. After this, you won’t have any more questions about what color liquid nitrogen dioxide really is. __________ 0:00 Demonstration of the setup for synthesizing liquid nitrogen dioxide 0:46 Start and an unfortunate incident during the synthesis 1:16 Synthesis of liquid nitrogen dioxide. 2:46 Demonstration of dinitrogen tetroxide. 3:38 Observation of dinitrogen trioxide formation. 4:57 Dissolution of liquid nitrogen dioxide in water. 5:32 Comparison of the reactions of nitrogen oxides with hydrazine 6:58 Reaction of liquid nitrogen dioxide with allylamine. 7:40 Barking Dog reaction but it's nitrogen dioxide 8:32 Reaction of sodium with liquid nitrogen dioxide. 8:56 Dinitrogen Pentoxide Teaser __________ ❤️ https://www.patreon.com/ChemicalForce ❤️

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Demonstration of the setup for synthesizing liquid nitrogen dioxide

Hey guys, today we are going to making liquid nitrogen dioxide using this setup you see here. In the left flask we have dry sodium nitrite. In the dropping funnel there is diluted hydrochloric acid. Between the drying column with phosphorus penttoxide and the main flask there is a solution of silver nitrate which is used to absorb any hydrogen chloride impurities. Dry nitrogen dioxide enters this free neck flask. Oonated oxygen is fed into it continuously which s oxidizes any nitric oxide impurities into nitrogen dioxide from the right outlet tube. Dry nitrogen dioxide flows into a glass test tube coil. During the process it's cooled with a mixture of ammonium nitrate salt and ice which gives a temperature of about 20° C below zero. So let's start

Start and an unfortunate incident during the synthesis

the synthesis. To do this we need to slowly add hydrochloric acid to the sodium nitrite. At the very start of the synthesis, there was an unfortunate accident. Pressure popped the stopper out of a dropping funnel and it fell right onto the gas outlet tube, breaking it.

Synthesis of liquid nitrogen dioxide.

So, I replaced the gas outlet tube and continued with synthesis. After a while, we can see how much liquid has collected in our glass test tube coil. Oh, look how the drops slide down the glass coil and collect in the test tube. In the end, we get a pretty good amount of greenish blue liquid. But this is not pure liquid nitrogen dioxide. It's a mix of blue ditrogen triioxide and brown nitrogen dioxide. Later, we will oxidize this mixture to get pure brown liquid nitrogen dioxide. When the glass test tube coil is almost full, the synthesis can be stopped. By the way, the flask with silver nitrate turned blue. This happens because nitrous acid forms in it and it has that color. So, I removing the beaker to show how much gas we managed to liquefy. In the end, we got more than half of this test tube coil. Now we are going to oxidize it using ozonated oxygen. To do this I directly connect it to an ozone generator and start passing oxygen with a high ozen concentration through this liqufied gas. At the same time the color of a liquid gradually changes from dark green to light green and after complete oxidation it finally becomes light brown. Look at this. This is liquid nitrogen dioxide. In the liquid state, it's mostly present as d nitrogen troxide, but for simplicity, I'll refer to it as liquid nitrogen dioxide. D

Demonstration of dinitrogen tetroxide.

nitrogen troxide has a pale yellow, almost colorless appearance. It forms when liquid nitrogen dioxide is strongly cooled. So, if I place a sealed ampule of it into liquid nitrogen, the amount of the nitrogen troxide will increase significantly and the liqufied gas will turn a pale yellow color. For a convenient demonstration of its reaction, I'll transfer it into a flask. From this flask, which will be kept in a cooling mixture, it's easy to draw the gas into a pipette. After I pour the liquid nitrogen dioxide into a flask, I place it in a nice salt bath. At this temperature, it can be stored well without noticeable evaporation.

Observation of dinitrogen trioxide formation.

So for the first experiment I want to show nitric oxide which I have frozen in this test tube. However, because of moisture and oxygen, we can also see blue and green colors in the test tube. These are impurities of other nitrogen oxides. Now if I bring a pipet with light brown liquid nitrogen dioxide to this test tube, its tip will instantly turn green due to the formation of the nitrogen triioxide. D nitrogen triioxide is dark blue in both its solid and liquid states. This is what liquid ditrogen triioxide looks like. Its formation can also be demonstrated in the reverse way. I'll pour a small amount of nitrogen dioxide into a test tube and insert a glass tube through which I'll pass nitric oxide. With this method, no visible changes occur. For a reaction between these nitrogen oxides to take place, the mixture needs to be cooled. Look, as soon as I direct a stream of liquid nitrogen onto the test tube, the color immediately changes to light green. This is the color of a solution of d nitrogen triioxide in nitrogen dioxide. Once all the nitrogen dioxide has reacted, the solution, the test tube will turn blue. This is pure d nitrogen triioxide.

Dissolution of liquid nitrogen dioxide in water.

When liquid nitrogen dioxide is added to water, nitric oxide forms right away. This is easy to see from the color change. The liquid goes from light brown to light green. I found the slow motion footage of this oxide dissoling in water really fascinating. So, I couldn't resist adding it to the video. This d nitrogen triioxide reacts much less actively with hydroin than liquid nitrogen dioxide does. Let's compare these reactions.

Comparison of the reactions of nitrogen oxides with hydrazine

I also carried out the reaction in complete darkness and recorded it in slow motion. hey, hey.

Reaction of liquid nitrogen dioxide with allylamine.

Not only hydroine, other amines also react very vigorously with nitrogen dioxide. As an example, I used an unsaturated amine, dialamine.

Barking Dog reaction but it's nitrogen dioxide

Now I'd like to ask you to explain the next experiment. Many of you probably know it. It's called the barking dog reaction. A reaction between carbon dulfide and nitrous oxide. But if you look up how to perform it, almost everywhere they suggest using nitrous oxide. I'm not sure why. This oxide is actually harder to prepare in the lab than nitrogen dioxide. And with nitrogen dioxide, the reaction works just as well. I would like it more because you can clearly see the brown gas loss its color. Write your thoughts about this in the comments.

Reaction of sodium with liquid nitrogen dioxide.

In this experiment, I'll pour a small amount of liquid nitrogen dioxide into a test tube and drop in a piece of sodium. Unlike nitric acid where sodium explodes instantly, the reaction here is much calmer. What do you think forms in this case? How do you write the reaction equation? Share your ideas in the comments.

Dinitrogen Pentoxide Teaser

Actually, I made this video to lead into my next one about d nitrogen penttoxide, the unhydride of nitric acid. I managed to capture the whole synthesis process and several reactions with this substance. So, make sure to subscribe to the channel and stay tuned. Also, if you can consider becoming my patron, I'm truly grateful for your support as it helps cover the cost of equipment, chemicals, and filming and makes it possible to keep creating new experiments. Thanks to you, we can all explore and share this rare and previously unseen chemical reactions together. Thanks for watching. See you next video.

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