Making Concentrated (68%) Nitric Acid

today we're going to be making a little bit of azeotropic nitric acid the nitric acid that you find in a lab is generally just the azeotropic type and this just means that it can't be purified or made stronger by distillation in the lab the azeotropic nitric acid is very useful for a lot of things in general but it's mostly used for reactions like nitration x' on my channel I've used it a few times in nitration x' like when I made 3-nitrophthalic acid or nitro benzene an attrition reaction is really just adding an no2 group to something and this is often very useful in organic chemistry and it's also useful for making explosives a lot of commonly known explosives like TNT are just highly nitrated organic compounds I don't really plan on making any videos on explosives but I do have a video already made on picric acid which is a tri nitrated phenol if you're interested in seeing how that reaction took place I provided a link to it in the description I needed the nitric acid to make mercury nitrate which would in turn be used to make mercury thiocyanate or the Pharaohs serpent I decided that I would revisit this video and instead of making 30 grams like last time I would make 300 so I've actually already made the 300 grams of mercury thiocyanate and I will post that in a future video here you can see what I use to make the nitric acid and on the left I just have some sulfuric acid drain cleaner and on the right I have potassium nitrate the sulfuric acid drain cleaner can be found in most hardware stores and you don't need to use potassium nitrate you can also use any other type of nitrate salt if you're living somewhere where ammonium nitrate is easily found in instant cold packs you might want to substitute the potassium nitrate for ammonium nitrate the procedure that I'm using for this video is taken from a Doug's lab video and I'm going to provide a link to it in the description I start off by adding 404 grams of potassium nitrate to a 1 liter round bottom flask on top of this I added in about 200 milliliters of distilled water with the water added I slowly pour in 232 milliliters of our sulfuric acid drain cleaner you'll probably notice that the color of the sulfuric acid is a little bit Brown and this is pretty typical of store-bought sulfuric acid drain cleaners the color can actually vary a lot from manufacturer to manufacturer and there's also different additives that's put in there but for this reaction it really doesn't matter I then put together a simple distillation setup and what we're going to try to do is distill off the nitric acid on the right side I've set up a little sodium hydroxide trap to collect any nitric acid vapors that might escape when we're ready we can turn up the heat but for now stirring isn't going to really work because there's a lot of undissolved salt as the reaction heats up though the salt should start to dissolve and we should eventually be left with a perfectly clear solution the reaction that's taking place here is pretty simple and we're just reacting sulfuric acid with potassium nitrate to produce potassium by sulfate and nitric acid the potassium by sulfate is a salt and will stay in the flask whereas the nitric acid will be distilled off with some water very shortly after boiling you can see that there's not very much potassium nitrate left and it won't be long until it's all gone as we reach the point where pretty much all of the potassium nitrate salt is gone you can actually see a red gas that's formed above as we look at the rest of the distillation apparatus we can actually see that it's filled with this reddish yellow gas this reddish yellow gas is nitrogen dioxide gas and it's perfectly normal and expected for this to be produced in the reaction as we continue to boil the reaction the reddish color should slowly diminish eventually we'll reach a point where there's no colored gas left in the apparatus and it's around this point that things will start to distill over at the beginning of the reaction we added 200 milliliters of water and for this reason at this point the nitric acid that comes over is going to be quite dilute and it's definitely not a zeotropic as the distillation continues the concentration of the nitric acid will increase until we're distilling azeotropic nitric acid at this point of about 68% nitric acid to 32% water we achieve the highest concentration of nitric acid that we can get by distillation so on the right side everything's looking good and we keep collecting our nitric acid which is tainted a little bit yellow due to nitrogen dioxide gas when we look at the boiling flask on the left side you can see it's starting to froth more and this is indicating that the reaction is coming to an end eventually we'll reach a point where there's not much water left in the flask and all of the potassium by sulfate will crash out it's at this point that the distillation is done so I remove the round bottom flask from the heating mantle and I let it cool down to room temperature when we look at the receiving flask we have a lot of very dilute yellowish nitric acid and we're going to need to purify this the salt that's left in the reaction flask is pretty solid but you don't have to worry too much because it's quite water soluble it can be easily cleaned out by rinsing the flask several times with hot water to purify the dilute nitric acid we don't use a simple distillation and instead we use a fractional at this point we're trying to selectively get rid of excess water and the fractional column really helps us do this as the vapors from the distillation flask travel through the column they will go through a cycle of condensing and re vaporizing every time this happens the fraction that's more volatile will be the one that's more likely to ravais per eyes and the less volatile one we'll be more likely to condense and stay condensed this will happen numerous times as the mixture of nitric acid and water vapors travel up the column and eventually at the top we should be left with mostly water this makes sense because water boils at around 100 C but the azeotropic nitric acid boils at around 120 C so it's the more volatile fraction and it should come over first the azeotropic nitric acid is less volatile so it condenses and falls back into the reaction flask once the excess water is being removed the azeotropic nitric acid can make it to the top of the column and distill over I should note that you don't absolutely need to carry out a fractional distillation and you could also use a simple distillation with a simple distillation though we don't really get as good of a separation between the two fractions with a fractional column pretty much all of the water comes over and then the azeotropic nitric acid comes over but with a simple distillation it's probably going to be mixed a little so with a simple distillation we're going to be mixing a little bit of the end of the excess water fraction with the beginning of the azeotropic nitric acid fraction you're going to end up losing a little bit of nitric acid as you wait for the excess water to fully distill off as we bring the nitric acid to a boil the first thing that's going to happen is it's going to expel a lot of nitrogen dioxide gas there's a lot of nitrogen dioxide gas impurity dissolved into the nitric acid but as we raise the temperature the solubility decreases and the gas is kicked out after we boil it for a bit we should be left with a completely clear solution the fractional column that you see here is called a Vig row column and you can see drops of our distillate reckon denting the distillate starts to come over and we collect it but at this point it's mostly just water when the temperature reaches about 120 C the beakers swapped for a round bottom flask and now we start to collect our azeotropic nitric acid one important thing to do with fractional distillation x' is to insulate the column and I do this using a little bit of aluminum foil the column is quite long and if left exposed to air it can be cooled enough that everything just recondense is in the column and never makes it over as we continue with the distillation the volume in the flask should slowly decrease once only a very small amount of distillate is left I turn off the heating in general it's important not to heat to total dryness because this can lead to overheating of the flask when all is said and done were left with 134 milliliters of slightly yellow azeotropic nitric acid this yellow color occurs because a little bit of the nitric acid degraded due to the heat of the distillation to me the yellow color isn't a big problem but if you want to clear it up you can bubble dry air through it until all of the nitrogen dioxide gas is expelled so here's what we're left as the two fractions of the distillation on the Left we have 134 milliliters of azeotropic nitric acid and on the right we have just a little bit of dilute nitric acid I actually really recommend keeping the dilute nitric acid for things like cleaning and not throwing it out I should also mention that the concentration of the nitric acid was confirmed by testing its density I did this like I did in different videos where I measured out a volume of about 10 milliliters and then I weighed it and I just figured out the density grams per milliliter from there the nitric acid was at a temperature of around 20 C and I got a density of about 1.41 grams a milliliter and this corresponds to a concentration between 68 to 69 percent just to test out the nitric acid I do the classic test where I react it with a little bit of copper very shortly after adding it we can see that there's a vigorous reaction occurring and this confirms that we have nitric acid you should also note the copious amount of nitrogen dioxide that's being led off so this really needs to be done somewhere that's well ventilated for storage I poured the nitric acid into an old acid bottle that I had all of the nitric acid that I made here is going to be used in an upcoming video where I made the Pharaoh serpent again and that should be released eventually

Channel: NileRed

Views: 754,850

Keywords: pharaoh's, pharaoh, serpent, how, to, nile, red, chemistry, tutorial, mercury, nitric, acid, azeotrope, azeotropic, nitrate, sulfuric, h2so4, no3, hno3, science, nilered

Id: KBeo8nww21g

Length: 10min 19sec (619 seconds)

Published: Wed Mar 23 2016