| Pages:
1
2 |
franklyn
International Hazard
Posts: 3026
Registered: 30-5-2006
Location: Da Big Apple
Member Is Offline
Mood: No Mood
|
|
As DraconicAcid observes above ,
Regardless how dense a vapor, if it needs to be much hotter
than ambient air temperature the boundary will be turbulent.
Why a refrigerant gas that boils at subzero temperature is
preferable. Something that is not too far from ambient temp.
might do, such as this _
1,1,2-Trichloroethylene
Boiling point: 86.7 °C
Vapour density: 4.53 (air =1)
From here _
www.environment.gov.au/atmosphere/airquality/publications/so...
It is being phased out of commerce and is increasingly hard to find as a technical
grade retail product. Try looking first at your local auto parts store for degreasers.
Another prospect and easy to make with Acetone and hypochlorite
Chloroform
Boiling point: 62 °C
Vapour density: 4.1 (air =1)
From here _
www.osha.gov/SLTC/healthguidelines/chloroform/recognition.ht...
An electronic circuit board flux remover might serve the purpose
1-bromopropane
Boiling point: 71 0°C
Vapour density: 4.3 (air =1)
From here _
www.cdc.gov/niosh/ipcsneng/neng1332.html
Other candidates
www.techspray.com/product-info.php?pId=31&cId=9
www.techspray.com/download-msds-document.php?pId=31&mId=...
www.techspray.com/product-info.php?pId=18&cId=9
www.techspray.com/download-msds-document.php?pId=18&mId=...
"Radio Shack" Rosin Flux Stripper
http://hpd.nlm.nih.gov/cgi-bin/household/brands?tbl=brands&a...
_________________________________
The compound kristofvagyok entertains
Vapour density: 3.3 (air =1)
has the right boiling point - 64 0°C
www.lookchem.com/Trifluoroacetonitrile
www.chemicalbook.com/ProductMSDSDetailCB5321126_EN.htm
MSDS link top of page here _
www.sigmaaldrich.com/catalog/product/aldrich/544078
.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
Not necessarily. Convection currents arise proximately due to differences in density. Temperature differences causes convection
currents in air (and other gases) because temperature differences cause density differences. With dissimilar gases, though, a denser gas will tend to
settle out underneath a less dense one, regardless of temperature. This separation is not a two-phase system, not exactly, because the boundary is not
a strict layer; there's some mixing. Nevertheless, if the molecular weight difference is high enough, the boundary region can be fairly narrow.
As to woelen's original question, I don't know that there's much that's inexpensive that satisfies all the other criteria. One class of substances,
however, that are readily available, though not terribly inexpensive, are the perfluorinated polyethers that are used for vapor phase soldering, and
at even higher molecular weights, for vacuum pump oils. Look up the Galden HT line. They need to be heated to vaporize, but it means you could make
your demonstration boat change height in a tall tube depending on the relationship of heat vs. cooling.
|
|
|
chemister2015
Harmless
Posts: 31
Registered: 25-2-2015
Location: Russia, Khabarovsk
Member Is Offline
Mood: No Mood
|
|
I collected information about all gases. Densest gases:
1) CF3CF2CF2CF=NOCF3
2) WF6
3) (CF3)3PF2
4) CF3OCF2CF2OCF3
5) Si3F8
6) C2F5OCF2CF2NO
7) C2F5OSF5
8) TeF5Cl
9) TeF5OF
10) (C2F5)2O
|
|
|
metalresearcher
National Hazard
Posts: 758
Registered: 7-9-2010
Member Is Offline
Mood: Reactive
|
|
WF6 ?
|
|
|
clearly_not_atara
International Hazard
Posts: 2792
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
I trust you are reasonably prepared for the hazards associated with practically all heavy gases!
But should you prefer a gas which is less dangerous, my entry is tetramethylsilane. Boiling point 26-28 C means that it can be stored
and shipped as a liquid but is easily volatilized. It is the NMR standard because all 12 protons are identical and look different from most organic
protons. Its toxicity is relatively low. MW 88. Minimal environmental hazard. Available in 25-gram quantities -- equivalent to several liters of the
gas -- for about 50 USD.
|
|
|
Rainwater
National Hazard
Posts: 925
Registered: 22-12-2021
Member Is Offline
Mood: Loving every second
|
|
The 11 year old me wants to make fart jokes.
CO2 will float an alumnium boat.
"You can't do that" - challenge accepted
|
|
|
| Pages:
1
2 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
