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I need a chemical suggestion for a lab
Posted by: pbarra1
Date: November 03, 2021 11:47AM
Designing a new lab. I need a chemical with a low melting point (below 150C, below 100C even better) that is insoluble in water and does not produce dangerous products when heated to decomposition. I will be in a hood for the heating part but want to be cautious working with students. Lauric Acid and Sulfur are already used elsewhere in the experiment so not those two. Suggestions appreciated.
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Re: I need a chemical suggestion for a lab
Posted by: wurm
Date: November 03, 2021 11:51AM
And this just shows the great diversity of this forum. From Macs to toilets to recipes to chemical suggestions, all in one forum.
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Re: I need a chemical suggestion for a lab
Posted by: mikebw
Date: November 03, 2021 11:56AM
Mercury comes to mind, but that as a vapor sounds pretty dangerous to me.
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Re: I need a chemical suggestion for a lab
Posted by: Paul F.
Date: November 03, 2021 12:02PM
Quote
mikebw
Mercury comes to mind, but that as a vapor sounds pretty dangerous to me.

I was going to say Mercury, too... up until that vaporizing part...
That's bad, BAD, BAD news... Like EPA super-fund site bad. Like condemn the building bad...



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Persistence is necessary for Excellence. And Persistence is a Decision.

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Re: I need a chemical suggestion for a lab
Posted by: Z
Date: November 03, 2021 12:26PM
Carbon bromide? Not zero solubility in water but pretty darn low

Melting point
94.5C; 202.0F; 367.6 K
Boiling point
189.7C; 373.4F; 462.8 K decomposes
Solubility in water
0.024 g/100 mL (30C)

Or Tin?



Edited 1 time(s). Last edit at 11/03/2021 12:27PM by Z.
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Re: I need a chemical suggestion for a lab
Posted by: pbarra1
Date: November 03, 2021 12:31PM
Z. I thought of that one but discarded it because I thought it was a liquid. Now I just have to see if we stock any. Thanks.
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Re: I need a chemical suggestion for a lab
Posted by: pbarra1
Date: November 03, 2021 12:39PM
Just checked the price of CBr4 - what other suggestions are out there?

Z, you mentioned Tin. Not pure Tin as the MP is too high. Were you thinking something else?
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Re: I need a chemical suggestion for a lab
Posted by: Diana
Date: November 03, 2021 12:42PM
I searched for “melting point experiment” and got several. Simpler organic compounds are usually used, and if you stick with those containing just carbon, hydrogen, oxygen and/or nitrogen you can be reasonably sure that the combustion products will be relatively benign. Do it in the fume hood (like you said before); and of course, always double check to see what decomposition products will be formed. Consider incomplete combustion may occur, and check it as well. Having said all that, melting point experiments are usually done on very small quantities (milligrams or so) and the expected products will be so small in quantity that it likely won’t make a lot of difference as long as you stay away from the toxic stuff.

Naphthalene, MP abt 80 C, BP abt 218 C. Smells like mothballs as it is the main ingredient of it.
Benzoic acid, MP abt 122 C, BP abt 250 C. The carboxylic acid group makes this one more soluble in water, but at 2-3 grams per liter it may not make a difference.

Keep in mind that the moities on the compound can make it more or less soluble in water. The larger the structure of the molecule the less likely it will be water soluble.

I’m sure there are more, depending on the range of temps you are wanting to work with. Sucrose (table sugar) would work as well.

Are you setting up a new laboratory experiment in an existing chemistry lab, or starting a new physical lab? You may find stuff you already have in the first instance, and probably want to go cheap(er) in the second instance.

Diana
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Re: I need a chemical suggestion for a lab
Posted by: MrNoBody
Date: November 03, 2021 12:46PM
Melting point too high @156.6C so Indium is out.
[pubchem.ncbi.nlm.nih.gov]
Good luck in this rabbit hole thumbsup smiley



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Re: I need a chemical suggestion for a lab
Posted by: Diana
Date: November 03, 2021 12:47PM
Quote
Z
Carbon bromide? Not zero solubility in water but pretty darn low

Melting point
94.5C; 202.0F; 367.6 K
Boiling point
189.7C; 373.4F; 462.8 K decomposes
Solubility in water
0.024 g/100 mL (30C)

Or Tin?

Most elements will have quite high melting points. The smaller and lighter the atom the more likely it will be either a gas or a liquid at room temperature. There are exceptions, of course.
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Re: I need a chemical suggestion for a lab
Posted by: pbarra1
Date: November 03, 2021 12:47PM
I am using sucrose elsewhere in the lab where I need a soluble material. I have naphthalene. There are many references that describe it as subliming but I now remember using it in a melting point lab many decades ago and its not soluble - thanks.
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Re: I need a chemical suggestion for a lab
Posted by: Filliam H. Muffman
Date: November 03, 2021 01:54PM
I was going to suggest plain wax before I looked up Lauric Acid. Naphthalene is very similar to Lauric Acid, but having multiple hydrocarbons with different densities and melting points might be worthwhile.

Wood's Metal won't blow up when heated but most of the component metals are toxic in varying degrees (50% bismuth, 25% lead, 12.5% tin, and 12.5% cadmium). Field's Metal is less toxic but expensive due to the Indium.
https: //www.belmontmetals.com/product-category/low-melting-fusible-alloys/



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Re: I need a chemical suggestion for a lab
Posted by: Bill in NC
Date: November 03, 2021 02:17PM
gallium?
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Re: I need a chemical suggestion for a lab
Posted by: ztirffritz
Date: November 03, 2021 03:12PM
[chemistrytalk.org]

Galium is relatively harmless, melts in your hand around 30°C.

[www.youtube.com]

edit: i removed a reference to "cool crystalline structures when it cool" because I think that was a different metal. Iridium?



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Edited 1 time(s). Last edit at 11/03/2021 03:13PM by ztirffritz.
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Re: I need a chemical suggestion for a lab
Posted by: PeterB
Date: November 03, 2021 03:26PM
I was gonna suggest hexane -- MP 69oC, highly insoluble in water, but you'd probably really have to heat it up a lot to get complete decomposition, and no idea if the products would be dangerous (I wouldn't have thought so)... but of course it's highly flammable...

The problem with naphthalene ... toxic by ingestion/inhalation ... may not be the smartest thing to be heating to decomposition. But then, chem labs do a lot of stuff that might be dangerous.

I always like experiments that involve "real life" substances. How about rather than a pure chemical, you use olive oil? MP -6oC, highly insoluble in water (obviously!), doesn't produce any nasty degradation products and degrades at relatively safe temperatures.




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Re: I need a chemical suggestion for a lab
Posted by: pbarra1
Date: November 03, 2021 04:02PM
PeterB: I need solids and hexane is not allowed on campus due to flammability.

FHM: I originally was going to use paraffin but its appearance is very different than all of the other materials and I dread students getting it stuck in test tubes and such.

Gallium is $62 / 2.5 g

I think I have enough materials to give the lab a test run on monday.

Thanks everybody.
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Re: I need a chemical suggestion for a lab
Posted by: Z
Date: November 03, 2021 04:56PM
Quote
pbarra1
Just checked the price of CBr4 - what other suggestions are out there?

Z, you mentioned Tin. Not pure Tin as the MP is too high. Were you thinking something else?

Not sure what I was thinking, other than a lower MP than lead. Not that it is within your bounds.
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Re: I need a chemical suggestion for a lab
Posted by: Buzz
Date: November 03, 2021 05:02PM
Saw this thread is passing this morning, and ignored it at the time.... not because it was none of my beeswax, but because I didn’t have time to respond.

BTW, my thought at the time was beeswax, and after now finally having a moment to spare, I’m gonna stick with that thought.
==
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Re: I need a chemical suggestion for a lab
Posted by: neophyte
Date: November 03, 2021 05:30PM
polycaprolactone
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Re: I need a chemical suggestion for a lab
Posted by: space-time
Date: November 03, 2021 09:43PM
something like this maybe?

[en.wikipedia.org]–indium
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Re: I need a chemical suggestion for a lab
Posted by: ztirffritz
Date: November 04, 2021 09:07AM
Quote
space-time
something like this maybe?

[en.wikipedia.org]–indium

That's the one I was thinking of!



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Re: I need a chemical suggestion for a lab
Posted by: Bernie
Date: November 04, 2021 10:42AM
Beeswax has a relatively low melting point range of 62 to 64 °C (144 to 147 °F). If beeswax is heated above 85 °C (185 °F) discoloration occurs.




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