Identifying an Unlabeled Chemical

[AzoMittle]

Hey guys I need a little help with something

 

 

I have a random bag of leftover, sealed chemical that I need to identify. It is a fine powder, white, and in 5 separate 1lb bags.

 

I know which order it came from so I can narrow it down to either Potassium Nitrate, Sodium Benzoate, or Strontium Carbonate; most likely one of the latter two.

 

How do I go about either confirming that it is one of those (or else confirm that it is not the other two)? I was thinking that if it's PN I could test it by making R-candy but I don't want to try that in case it ends up being one of the other two. I don't have any other chemicals on hand at the moment besides Iron (III) Oxide (and sugar, or common household stuff).

 

Could I test the pH? I would need to buy a pH test but that would be simple.

 

What about a solubility test?

 

What should I absolutely avoid doing for safety reasons?

 

edit: spelling correction

 

 

Thank you all

Edited September 27, 2013 by AzoMittle

[Shadowcat1969]

Off the top of my head Strontium Carbonate is practically insoluble in water, the other two are. So if you put a little in water and it doesn't disolve, that points to Strontium Carbonate rather than the other two. As long as you are CERTAIN that it could only be one of these three, that would be my first test and will let you know how to proceed from there.

[WSM]

Hey guys I need a little help with something

I have a random bag of leftover, sealed chemical that I need to identify. It is a fine powder, white, and in 5 separate 1lb bags.

I know which order it came from so I can narrow it down to either Potassium Nitrate, Sodium Benzoate, or Strontium Carbonate; most likely one of the latter two.

How do I go about either confirming that it is one of those (or else confirm that it is not the other two)? I was thinking that if it's PN I could test it by making R-candy but I don't want to try that in case it ends up being one of the other two. I don't have any other chemicals on hand at the moment besides Iron (III) Oxide (and sugar, or common household stuff).

Could I test the pH? I would need to buy a pH test but that would be simple.

What about a solubility test?

What should I absolutely avoid doing for safety reasons?

edit: spelling correction

Thank you all

 

If it's either sodium benzoate or strontium carbonate, add a drop of vinegar to a pinch of the powder. If it bubbles, it's likely the carbonate.

 

If some is dissolved in hydrochloric acid (pool acid) a flame test would either be lavender (potassium), yellow (sodium) or red (strontium).

 

If you mark your containers better, these problems will be avoided in the future.

 

WSM

Edited September 27, 2013 by WSM

[pyrokid]

My strontium carbonate has a chalky consistency, while my potassium nitrate is very much like salt or sugar.

 

I like the idea of a flame test.

[AzoMittle]

 

If you mark your containers better, these problems will be avoided in the future.

 

WSM

 

Agreed, I decided to mark the container it was being stored in rather than the bags themselves. Lesson learned.

 

A flame test sounds fairly definitive though pool-grade acid may have additives so I'll start with the vinegar/water. Should I just dissolve equal parts chemical and acid and immediately take a mini-torch to it? It won't have troubles lighting while wet?

[WSM]

Agreed, I decided to mark the container it was being stored in rather than the bags themselves. Lesson learned.

A flame test sounds fairly definitive though pool-grade acid may have additives so I'll start with the vinegar/water. Should I just dissolve equal parts chemical and acid and immediately take a mini-torch to it? It won't have troubles lighting while wet?

 

I learned MY lesson long ago...

 

Typically pool acid is nearly straight HCl, diluted with water to the concentration sold. It's not exactly pure, but pure enough. The flame test requires an inoculating loop made of platinum or nichrome wire dipped in a solution of the material to be tested. Then the drop on the loop is placed in a clear flame with a dark background behind it. Lacking regular lab equipment, an idling propane torch with a blue flame (and no flecks of other colors [yellow usually]) works well for the flame source. The dark background aids in spotting subtle colors otherwise obscured by a lighter background.

 

To be certain your flame tests are accurate, test known materials before you test the unknown, to give yourself an idea of what you're looking for. Good Luck!

 

WSM

 

Good judgement comes from experience. Unfortunately, too much of that comes from bad judgement !

[AzoMittle]

 

The flame test requires an inoculating loop made of platinum or nichrome wire dipped in a solution of the material to be tested. Then the drop on the loop is placed in a clear flame with a dark background behind it. Lacking regular lab equipment, an idling propane torch with a blue flame (and no flecks of other colors [yellow usually]) works well for the flame source. The dark background aids in spotting subtle colors otherwise obscured by a lighter background.

 

 

Hmmm, I get the general idea of what you're saying but based on that I couldn't actually perform a flame test (as in not sure of the exact steps). Could you please link me to a step-by-step or a video example or preferably both? Is this how most flame tests are done?

 

I would prefer to do this the "lab" way so as to learn how to actually do it, plus never know when I may need to do it again; hopefully not under the same circumstances.

As long as "regular lab equipment" doesn't require big $$$ I don't mind acquiring equipment. It sounds like to do this up proper I would need:

* nichrome/platinum wire

* a decent video camera

* proper lighting (or lack thereof)

* HCl acid

* a decent propane torch

 

Thanks for all the help! Hopefully no more mystery chemicals from here on out

[psyco_1322]

Azo, just smell it. Benzoates have a very distinctive smell, while the other two chems will not really smell at all. Otherwise, do as Shadowcat said, try dissolving some into water, the KNO3 is going to be very soluble and the carbonate is not going to really dissolve into water at all. Super simple, and doesn't require anything special at all.

[AzoMittle]

I like you.

[AzoMittle]

Okay so it dissolves in water. No (noticeable anyways) bubbling with the vinegar. No smell. It's about as fine as confectioner's sugar.

 

Edit: Just mixed up 5grams of "r-candy". Will update soon.

 

Update: It takes a flame, not easily, and burns a little before going out. Just 2:1 (by volume) of sugar to mystery chemical. I think the flame test may be necessary.

Edited September 29, 2013 by AzoMittle

[Seymour]

That sounds well within the possible range of what scratch mixed KNO3/Sugar can do. If it burned at all pyrotechnically, even if poorly and then it went out, it's certainly not Sodium benzoate or Strontium carbonate. If those three are all that it could be, I'd say you have your answer

[taiwanluthiers]

By the way strontium carbonate burns very well with MgAl or Mg, with a nice red flame. It does not burn pyrotechnically with any organic fuel however.

[Mumbles]

The flame test will basically confirm the presence of either sodium or strontium. The potassium flame is fairly faint, and can be easily missed if you don't know exactly what to look for. This is even more a factor with homemade setups. Nichrome or platinium are ideal. I've actually been able to get acceptable results from stainless steel wires or needles. It's not the best, but for powerful flame colors it works just fine.

 

The best way to do this would be to confirm it via multiple tests. Do you by any chance have known samples of all of the chemicals in question to provide positive controls?

 

Strontium carbonate will fizz with vinegar or most acids, be insoluble in water (more or less), and give a nice red flame test. For a flame test, you'll need to dissolve it in an acid. HCl is the best for this, but vinegar might still yield a red/orange enough flame to be identifyable. Most strontium carbonate is contaminated with sulfides and sulfates. The sulfates wont dissolve, and the sulfides will react with acid to make something that smells like rotten eggs. Do this part outside.

 

Sodium benzoate is fairly soluble in water (63g/100mL at room temp), and will give a nice yellow flame test. Don't dissolve this in HCl for the flame test. Sodium doesn't require chlorine for the flame color. It will also react with HCl to generate sodium chloride and benzoic acid (Which is more or less insoluble in cool water). This might be another way to identify it positively. The reaction is rather pretty as well.

 

Potassium nitrate might be one of the most difficult to positively identify. It's moderately soluble in water (~30g/100mL at RT). The potassium flame isn't the most identifiable, and is easily overpowered by small amount of impurities. When you try to dissolve it in water, it will probably cool off, so that might be something to look for. RCandy or a simple small smoke bomb with sugar probably would be the best way to tell what it is. You'll basically have to figure this one out by process of elimination, and confirmation with something that burns.

[AzoMittle]

I unfortunately do not have any control samples.

 

I'm fairly certain that it is not Strontium Carbonate at this point. I can't get it to fizz with any of the vinegars I have laying around my kitchen, no smell either.

 

I'm going to do the flame test, I'll try to catch it on video with a black background but not sure how well it will show up. I picked up some 31% muriatic acid and a handheld propane torch, still need to get nichrome/platinum wire.

 

I'll update again next weekend hopefully.

 

edit: I went to half a dozen hardware and pool supply stores, none of them carried HCl pool supplies (only sulfuric acid, sodium bisulfate, and a few with long o-chem names that I didn't recognize). The 31% was the purest, and only one, I could find; it was being sold as Concrete Etcher.

Edited October 7, 2013 by AzoMittle

[Mumbles]

31% is about as concentrated as it gets commercially. Hydrochloric acid is actually a gas dissolved in water to make the acid. You can get the concentration up to around 38% with low temperatures and some work, but that will slowly release gas if allowed to warm to RT. About 31% is the most common grade sold, and usually pretty clean. You might notice it has a slight yellow to green color. This is cause by small amounts of free chlorine and iron impurities, but nothing to worry about. What you have is basically what all home chemists use as HCl.

[AzoMittle]

Cool! Thanks Mumbles, informative as always . Is the iron added on purpose or is it a byproduct of production methods or why is that in there?