Sciencemadness Discussion Board

Things learned in the lab

UnintentionalChaos - 19-12-2009 at 20:28

If you're anything like me, when you're messing around in your lab, you get some weird, unexpected result and end up going on a literature chase to try to explain it....or you found something after a long literature search and it turns out to be not so valid when you try it. Let's hear a few of yours.

Two of mine:

Any reference in the literature to antimony being attacked by hot, concentrated HCl is a load. Maybe if you're working with ultra fine powder, but 40 minutes of reflux didn't notably change crushed antimony about the texture of coarse sand.

While using Na2S2O5 to reduce MnO2 in solution, I started getting a coarse gray ppt about the texture of sand that turned my beaker of liquid into paste. Well, it turns out that I'd unintentionally made gravegliaite, the trihydrate of manganous sulfite.

http://rruff.geo.arizona.edu/doclib/zk/vol197/ZK197_97.pdf

The solution is to start chucking in concentrated acid to displace the sulfite anion, which it does fairly readily.

Sedit - 19-12-2009 at 20:48

Good Idea for a thread UC since more often then not the greatest joy of chemistry to to stumble on something you just didn't expect.

One of mine would have to be the extremely low temperatures that Snow and HCl mixture reaches. I was just messing around with various salts like NaCl and what not to see what kind of temperatures I could achieve when I decided to add HCl to snow and was completely shocked (and frozen:D) when the cup I held in my hand quickly dropped to -48degrees F:o. I surely did not expect this and a quick literature search showed that others performed this experiment many moons ago achieving simular results. I think the 15 inches or more of snow outside means I may revive the experimenting on this tommorow matter of fact.

UnintentionalChaos - 19-12-2009 at 21:43

Quote: Originally posted by Sedit  
Good Idea for a thread UC since more often then not the greatest joy of chemistry to to stumble on something you just didn't expect.

One of mine would have to be the extremely low temperatures that Snow and HCl mixture reaches. I was just messing around with various salts like NaCl and what not to see what kind of temperatures I could achieve when I decided to add HCl to snow and was completely shocked (and frozen:D) when the cup I held in my hand quickly dropped to -48degrees F:o. I surely did not expect this and a quick literature search showed that others performed this experiment many moons ago achieving simular results. I think the 15 inches or more of snow outside means I may revive the experimenting on this tommorow matter of fact.


Thanks for reminding me....I have tons of fluffy snow, a -20C freezer, and a 10lb pail of MgCl2*6H2O...and an ultra low temp thermometer to measure it with. I'm storing it in the -20C freezer because room temperature is at the very top end of the thing and I dont need it to overheat.

[Edited on 12-20-09 by UnintentionalChaos]

The_Davster - 19-12-2009 at 21:57

Quote: Originally posted by UnintentionalChaos  

Two of mine:

Any reference in the literature to antimony being attacked by hot, concentrated HCl is a load. Maybe if you're working with ultra fine powder, but 40 minutes of reflux didn't notably change crushed antimony about the texture of coarse sand.



Sorry to have to say this, but it does dissolve in HCl, and indeed it does require very finely divided antimony. A bit of the powder will even dissolve overnight in room temperature conc. HCl.:P

I was making a series of tungsten alkoxides from tungsten hexachloride and alcohols and upon trying it with a phenol realized that the colour of the product changes depending on whether an alcohol or phenol is reacting with it. A neat little indicator discovery. Never found anything in the literature about it...

Some of you may remember my old thread where I found out the hard way that unlike dilute acid and aqueous hypochlorite, conc. sulfuric and solid hypochlorite does not make chlorine, it makes chlorine dioxide...:o (The scar has finally gone! :D )

[Edited on 20-12-09 by The_Davster]

crazyboy - 19-12-2009 at 22:49

A while ago I learned about passivation, , it turns out just upping the concentration of acid doesn't always help attack the metal, sometimes it makes it harder. I knew about passivation before but I had never actually experienced it. A bit counter intuitive that dilute acids would attack metals less than highly concentrated ones but it's true.

len1 - 20-12-2009 at 04:18

Quote: Originally posted by Sedit  
Good Idea for a thread UC since more often then not the greatest joy of chemistry to to stumble on something you just didn't expect.

One of mine would have to be the extremely low temperatures that Snow and HCl mixture reaches. I was just messing around with various salts like NaCl and what not to see what kind of temperatures I could achieve when I decided to add HCl to snow and was completely shocked (and frozen:D) when the cup I held in my hand quickly dropped to -48degrees F:o. I surely did not expect this and a quick literature search showed that others performed this experiment many moons ago achieving simular results. I think the 15 inches or more of snow outside means I may revive the experimenting on this tommorow matter of fact.


This is very interesting - I didnt know. Ive read about HNO3 and ice - but that is wasetful as HNO3 is expensive, and is needed concentrated for most purposes. Not so HCl.

Can you please provide more info. What were the initial snow and HCl temperatures, what ratio did you use?