Forensics C

[chemguy]

It would definitively tell the difference between NaCl and sucrose by forming AgCl ppt with the former. Of course a flame test would work as well but I never like to rely on those.

[soccer_5456]

yeah flame tests are always blah with so much sodium contamination..and we were given candles to do flame tests with not bunsen burners so that was awful

[Phenylethylamine]

yeah flame tests are always blah with so much sodium contamination..and we were given candles to do flame tests with not bunsen burners so that was awful

Ugh, candles... They're rarely, if ever, actually hot enough to see anything.

Flame tests can be quite reliable identifiers for the ones that have really visible flame colors (e.g., lithium, potassium), but everything else is just a little too subtle unless they give you really good testing conditions (an actual Bunsen burner in a darkened area of the room). Last year at Nationals, we did get a Bunsen burner (one for every four teams, I believe), but it was set up directly in the sunlight from the giant windows at one end of the lab, and it was very difficult to see.

[meggers1221]

Does anyone have a good site for mass spec? that's what my partner and i are struggling with the most...

[meggers1221]

also for the burn test results for plastics, are those something you can find online, or should i actually burn the plastics previous to the competition?

[AlphaTauri]

Look online - just search up "plastics burn test results" and it's pretty easy to find them, plus actually burning some of the plastics can release toxic or otherwise hazardous fumes, as well as being a pain to clean up if it melts and drips all over your table.

[haverstall]

also for the burn test results for plastics, are those something you can find online, or should i actually burn the plastics previous to the competition?

Just reiterating what Alpha said, NEVER BURN PLASTICS. Make sure you know the densities of the plastic samples. Sometimes you can just identify based on that information.

Does anyone have a good site for mass spec? that's what my partner and i are struggling with the most...

I'm actually having the same problem. I really have no clue how to identify and am usually guessing based on my previous results.

[Phenylethylamine]

Does anyone have a good site for mass spec? that's what my partner and i are struggling with the most...

I'm actually having the same problem. I really have no clue how to identify and am usually guessing based on my previous results.

By googling "mass spectrometry", I got (among others) this link, which looks pretty good. I don't know how helpful that particular page would be, but I recommend using Google.

[salcedam]

yeah flame tests are always blah with so much sodium contamination..and we were given candles to do flame tests with not bunsen burners so that was awful

Ugh, candles... They're rarely, if ever, actually hot enough to see anything.

Flame tests can be quite reliable identifiers for the ones that have really visible flame colors (e.g., lithium, potassium), but everything else is just a little too subtle unless they give you really good testing conditions (an actual Bunsen burner in a darkened area of the room). Last year at Nationals, we did get a Bunsen burner (one for every four teams, I believe), but it was set up directly in the sunlight from the giant windows at one end of the lab, and it was very difficult to see.

If you're having trouble seeing the color of the flame test because of sodium contamination, use cobalt blue glass and look at the flame through the glass. Not sure if you do that already, but if you don't, you should try it out. What the cobalt blue glass does is absorb the yellow color the sodium ion gives off, leaving any other colors to be seen if there are any other colors that the powder would give off. So when you look at a sodium compound through the glass, you won't see any color, but any other compound that gives a color, you should be able to see since the blue won't absorb anything but yellow.

[Phenylethylamine]

yeah flame tests are always blah with so much sodium contamination..and we were given candles to do flame tests with not bunsen burners so that was awful

Ugh, candles... They're rarely, if ever, actually hot enough to see anything.

Flame tests can be quite reliable identifiers for the ones that have really visible flame colors (e.g., lithium, potassium), but everything else is just a little too subtle unless they give you really good testing conditions (an actual Bunsen burner in a darkened area of the room). Last year at Nationals, we did get a Bunsen burner (one for every four teams, I believe), but it was set up directly in the sunlight from the giant windows at one end of the lab, and it was very difficult to see.

If you're having trouble seeing the color of the flame test because of sodium contamination, use cobalt blue glass and look at the flame through the glass. Not sure if you do that already, but if you don't, you should try it out. What the cobalt blue glass does is absorb the yellow color the sodium ion gives off, leaving any other colors to be seen if there are any other colors that the powder would give off. So when you look at a sodium compound through the glass, you won't see any color, but any other compound that gives a color, you should be able to see since the blue won't absorb anything but yellow.

My issue was not sodium contamination, but rather too much sunlight in the test area.

For soccer_5456, however, yes, that is what the cobalt-blue glass is for.