post your favorite chemical reactions

hello all, I'm new to this forum, and have a huge interest in conducting some chemical experiments at home this christmas during my break from college.

I would greatly appreciate it if you posted your favorite chemical reactions that give really cool reactions; making sure to give both the chemical name (aka potassium nitrate) and common name if there is one (aka saltpeter) for the reactants.

Please be sure to give any advice on precautions or imporvements that can make the experiments safer and/or more enjoyable.

I hope to become a part of this forum and learn the scientific terms ya'll use .

This is also a great way for this forum to compile all the good experiments it has done, post pictures, and discuss them.
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I myself have thoroughly enjoyed trying to make rocket engines, by mixing potassium nitrate with sugar and boiling it down untill it is a pla-do like substance. I then shape it into the desired shape and light it off to hiss and large puff of smoke.

KNO3 + C12H22O11

I have also tried making thermite using homemade aluminum dust and rust, however haven't succeeded in this one yet. (any suggestions?)





[Edited on 14-12-2006 by LawnMaster1]

What comes to mind right now is KI in solution to which a little Pb(NO3)2 is added. PbI2 falls out as a wonderful yellow-orange precipitate - swirling around like a snow globe full of golden spangles!


Don't forget the other half of this wonderful expt,,,, When you get that nice orange precipitate and dry it then heat it strongly it turns into a beautiful purple cloud of iodine crytals and a puddle of melted lead!!!

[Edited on 15-12-2006 by Maya]

Wow!... I've never tried that before. I'll definitely have to do that - good excuse to make up some more PbI2.

I finally got around to making some copper soaps. Since I have been cooking since I was 10 and didn't get into chemistry until somewhat recently, I apologize for my constant use of cooking terms. It never occured to me, but the soapmaking (which I do as a hobby anyway) is a very interesting reaction. For those of you who are artsy as well as chemically inclined, homemade soaps are a dirt cheap holiday gift that nobody sees coming (and nobody has complained about at all yet ). Here's how I proceeded in making the copper soaps.

200grams of canola oil (rapeseed for those of you in europe) were placed in a large beaker. In another beaker, 70ml of water were placed. Based on saponification values, 28grams (slight excess) of sodium hydroxide were added to the water (NOT the other way around...same bad idea as adding water to acid) and stirred until it fully dissolved. Once the hydroxide solution cools to about 50C, heat the oil to the same temperature. The hydroxide solution cools MUCH slower than the oil can be heated. This mixture was agitated massively using an immersion blender for a few minutes (stirring is no good unless you have a long time to stand there and stir rapidly...stirbar is useless) until the "soap" thickens. This is called tracing because drops of soap will not sink immediately into the rest of the mix leaving a "trace" For this application you can go until it resembles pudding though for hand soap, this is a really bad idea. This was placed in a water bath and maintained at about 93C for 4 hours, adding water periodically when it appeared to be getting silghtly dry). The heat accelerates the saponification reaction and can bring it to completion in a few hours whereas the standard "cold process" soapmaking takes 2-4 weeks to completely react. The soap was then mixed with around 5 times its volume in water and blended with the stick blender into a thick paste. 90grams CuSO4*5H2O were dissolved in the minimum amount of water possible and this was stirred into the soap paste. Immediately, the soap coagulates into globs of blue-green, water insoluble, copper soaps. This has an awful habit of sticking to everything, so unless you have a lot of heptane, benzene, or heptane to waste cleaning everything, plan to throw out the containers you use from here on. Plastic wrap is very helpful. Since the oil used was canola, the majority of this soap is a mix of copper oleate, copper linoleate, and copper linolenate. Collect the soap (gloves! this stuff is so much worse to get on your hands than pine sap) in a big glob and place it on plastic wrap. In order to remove the sodium sulfate and glycerin contamination in the soap, add it to several times its volume in water in a large beaker. Heat the water until the soap melts (definetly below the boiling point of water) and the water clouds. Mix the soap around to try to expose as much of it as possible to water in order to wash out the soluble sulfate and glycerin. The soap does not like to stick to glass when liquid in the presence of any thin films of water so you're in luck at this stage. It also does not like to stick when chilled to freezer temperatures (which is where I'm storing it) because it becomes hard and rubbery (but still easily breakable). Pour the melted soap into an ice bath and wait for a decent layer of solid to form so it can be removed from the bath and freeze it. This soap still has significant water contamination, so dry by any method of your choosing (If I had a vacuum pump, that would be my choice, but i heated it in the oven at 90C for many hours. A very interesting and very messy experiment up to this point, though I found it completely impractical for making candles. I started with a 1:16 ratio of soap to wax, but no color was observed. By 3:16 ratio, the wax no longer hardened correctly when cooled, yet still no color. I have temporarily put the experiment on hold with the mix at 1:4 because it solidifies into a very thick, rapidly melting paste when cool which is impractical for anything more than a demonstration. (perhaps a jar candle could still be plasible). It shows some color, but is still noticably yellow from the wick burning. I will continue to experiment with it in the future, but have called it off for the moment. I froze the whole block of wax in the freezer, which makes it manageably hard.

Holy shit, can I talk. Anyway, for those of you interested in making your own soap for actual home use, I recommend this site. http://www.thesage.com/calcs/lyecalc2.php It does the simple calculations with saponification values for you. (Saponification values being how much KOH it takes to fully saponify a kg of a given oil, a derivative of molar ratios and the types of fatty acids in a given oil). Canola oil is actually a bad choice. You can use it for 1/4 of a soap batch's fat without ill effect, but more will make a soap that quickly goes rancid and stays fairly soft. KOH also makes a soft soap, so NaOH is preferred. Coconut oil, Palm oil, and palm kernel oil all make for a hard bar that lathers extremely well. Olive Oil also makes for a hard bar. Best of all is to include a little castor oil (look for laxatives in your local pharmacy) for its moisturizing and foaming properties. My standard mix is a combination of about a third coconut, a quarter olive, a quarter canola, and a sixth castor. Do not work in batches smaller than a pound of fats because it will cool too rapidly and have issues reacting properly. Before you do any of that, you need a mold. A good one is an old pringle can for round soaps or a shoebox (though these fit batches of about 3 pounds of oils better) In the case of the pringle can, lubricate the inside with a little extra oil to keep the soap from sticking. You could use petroleum jelly, since that can not be saponified, though regular oils are just fine. For a shoebox, drape a trashbag or plastic wrap with a little oil on it into the box. Mix the calculated amount of lye (I like the measurement for 7% extra fat) with the maximum amount of water the calculator reccomends and then heat the oils. Mix them together (This big a batch can be whisked for about 15 minutes or the blender can do the same job in a minute) until trace. You can add a tablespoon or two of extra glycerin to make it more moisturizing. An important addition is a teaspoon of vitamin E acetate (tocepheryl acetate, available as a beauty product) to keep extra oils from going rancid and also to make it even more moisturizing. Some soaps (most) get an oily odor when stored, so essential oils are usually added. A tablespoon per pound of oil is usually plenty, though not all essential oils are compatible with soaps. To avoid doing research for a first batch, pure lavender oil is compatible and cheap. Pour the mix into the prepared mold and insulate with towels to contain heat. The soap will set, then heat up and liquefy (gel stage) as the saponification continues to occur. This may occur 24 hours later or within a few hours of pouring. In this reaction, fats are disassembled into fatty acids and glycerol. Glycerol combines with the hydroxide ions and becomes glycerin. The fatty acids combine with the sodium and become soap. Since these soaps are one fatty acid and one metal ion, they have a nonpolar end and a polar end, making them very useful at removing oily dirt when washing hands. A copper soap should have two fatty acids to every metal ion and therefore is (I imagine) a rod shape (although unsaturated fats will produce a spiral galaxy shape...not sure what to call that)with two hydrophobic ends, and therefore is water insoluble. In a few days, remove the soap from the mold (tear away the pringle can or other improvised mold, if it is a contained shape) and cut into bars. Place these in a well ventilated place for two to four weeks to allow the saponification to come to completion. The surface exposed when poured will develop a film of sodium carbonate from air contact. Give away your very cheap gifts and save funds for labware and chems.

Well, why not the bother to make soap? it's another interesting reaction to follow. The low melting points are not something that crossed my mind, however. (I could go find lard or tallow at a butcher and use that for a harder soap, however) Thus, I forsee another mess about to happen and more heptane being used to wash everything afterward. My mention of fragrance is for making usable soap from starting materials (NaOH, water, and oil) if one should be so inclined. I'm not sure if you were making a reference to that or not.

I'm not trying to make a blue flame. Normal candles will burn with some blue flame and some yellow. The point of adding copper soaps is that when they burn, copper particles are released into the flame, changing it to a green color (standard color for copper non-halide complex compounds). A side effect is that very fine copper particles are deposited on the wick and crackle as they are burnt into oxide. Perhaps this could be done intentionally too, but I seriously doubt that a little copper powder can change the color of the flame. I've been doing another experiment with copper chloride to try to make blue flames, by "basting" the wick repeatedly at intervals to allow drying with CuCl2 in alcohol until it is quite saturated. This, when placed into a candle is not enough to change the flame color. I then tried using the wick, then a few quick dips of wax and rolling in more CuCl2 and then repeating. 2 rolls in CuCl2 powder along with the wick produces small amounts of blue green flame (because CuCl2 is a halide complex salt (chloride, flouride, iodide, bromide, etc.) With more repetitions, I should be able to make the blue-green more pronounced, though it will probably never dominate the flame's color.

Also, I imagine the lead soap candle would be an interestingly dangerous experiment. As was mentioned before, LOTS of ventilation for that one. Of course, any (that I know of) soap that is not an alkali metal soap (not made with sodium or potassium, the standards for making soaps for washing, or technically lithium, rubidium, or cesium (no way I'd waste those anywhere near soaps...well maybe lithium for a candle type experiment) will be water insoluble, and obviously not for washing one's hands

There should be minimal hydroxides left in the candle as they attach to the glycerol to make glycerin and are washed away (mostly) when I melted the soap in a water bath to wash it. You misunderstood the problem a bit there.

PS: I'm starting to wonder if it is even possible to get a true green flame from this or if it will always be quite yellow. The crackling is quite neat, though Maybe I should try starting with a potassium soap instead to avoid possible sodium contamination.

[Edited on 1-5-07 by UnintentionalChaos]

I post here so much it must be verging on spam

A reaction I just remembered that helped get me into chem is mixing an iron salt with gallotannic acid. The iron salt was homemade iron acetate made by placing rusty iron scrap into vinegar with some table salt. The gallotannic acid was made by boiling oak bark and acorns in water. Pomegranate skins would also have been an acceptable substitute. A very small amount of the tannic acid solution was added to a huge volume of water. Then, a bit of iron acetate solution was drizzled in. It immediately turns intensely black wherever the iron solution moves as a black compound ppts. This is better known as iron gall ink, arguably the most important ink in western civilization. No two sites seem to agree on what compound is actually formed. I see ferric tannate, iron pyrogallol, and ferric gallic acid complexes all listed as what the coloring matter may be. Whatever it is, it sure is interesting (and can dye cotton a very permanent dark gray/black).