jimmyboy
Hazard to Others
Posts: 235
Registered: 1-3-2004
Location: Texas
Member Is Offline
Mood: No Mood
|
|
Antifoaming agents
Anyone know how to cheaply reduce foaming - I am working with calcium chloride in a solution being boiled and it foams like crazy - what could i use
to flatten this out.
thanks
|
|
|
Tacho
National Hazard
Posts: 582
Registered: 5-12-2003
Member Is Offline
Mood: No Mood
|
|
A drop of silicone oil.
|
|
|
chemoleo
Biochemicus Energeticus
Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline
Mood: crystalline
|
|
Shouldnt oil in general work? I mean, oil that is lighter than the mix below - so that it prevents bubbles from forming?
Just try it out - put a bit of sunflower oil on top of your mix, and see whether you still get the foaming... I'd doubt it very much.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
|
|
|
Tacho
National Hazard
Posts: 582
Registered: 5-12-2003
Member Is Offline
Mood: No Mood
|
|
I have nothing to back me up on this, but I believe silicone oil is special in its anti-foaming properties. I believe it goes beyond the fact that it
floats, mechanically preventing foam, it has something to do with surface tension changing. But this may all be misfiring synapses of my collapsing
brain.
Besides, it's very unreactive, although this is not an issue with cacium chloride.
It is a nightmare to totally remove it from glassware though. About this I'm sure.
[Edited on 1-6-2004 by Tacho]
|
|
|
unionised
International Hazard
Posts: 5104
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
This might not be practical, but it works. point the flame from a blowtorch at the foam, the heat bursts the bubbles.
|
|
|
chemoleo
Biochemicus Energeticus
Posts: 3005
Registered: 23-7-2003
Location: England Germany
Member Is Offline
Mood: crystalline
|
|
Another one I like to do is use high vacuum (although not entirely practical), or a quick round of high g centrifugation... although not applicable in
a solution that is being boiled.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
Here's a topic that I thought might be worth revisiting. As I searched through the threads I noted that indeed there have been many situations in
home chemistry where foaming is a problem. For example when I make nitric acid the foam must be carefully controlled during distillation to prevent
an overflow into the condenser, ruining the product.
Yesterday during distillation of N,N-dimethylaniline foaming became a severe problem. To deal with it I added a Claisen head and carefully controlled
the heat to just keep the foam from entering the condenser (see picture below). This got me thinking that there might be a better way and I thought
back on my experience in industry where we used "defoamers" or "antifoams." These are liquids, often silicone oils/emulsions, added in very small
quantities on a continuous basis. Eg:
http://www.dowcorning.com/applications/search/default.aspx?R...
At the top of this thread Tacho has already suggested the same idea. A small dropping funnel or similar could be set up to add the defoamer by the
drop as required.
Any other comments or suggestions? How do you control foam?
[Edited on 11-10-2010 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
ScienceSquirrel
International Hazard
Posts: 1863
Registered: 18-6-2008
Location: Brittany
Member Is Offline
Mood: Dogs are pets but cats are little furry humans with four feet and self determination! 
|
|
You mean this sort of stuff.
http://www.hopandgrape.co.uk/catalog/detailV2_8.asp?itemid=B...
|
|
|
kmno4
International Hazard
Posts: 1495
Registered: 1-6-2005
Location: Silly, stupid country
Member Is Offline
Mood: No Mood
|
|
In a factory we use polyethers as antifoam agent.
Namely it is Pluronic xxx (I do not remember digits) from BASF.
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
I use a silicone oil that is the byproduct of the rotavap of its mixture with petroleum ether, used it last just a couple hours before seeing this
topic. Used it all weekend too, making an alkaline distillate of N. rustica extract. It works OK not great, but then it was sold as a lubricant.
I've been meaning to try castor oil but always forget when I go to the store, since I don't visit the laxatives area. I'm not sure I'm comfortable
with the cashier noting it, like I would take a laxative under any circumstances or even worse have someone else drink it.
[Edited on 13-10-2010 by S.C. Wack]
|
|
|
Panache
International Hazard
Posts: 1290
Registered: 18-10-2007
Member Is Offline
Mood: Instead of being my deliverance, she had a resemblance to a Kat named Frankenstein
|
|
Add 1% octyl stearate, cheaply and readily bought as the defoaming additive for the 'home do it yourself carpet steam cleaners' you hire at the
supermarkets and elsewhere, bottle is like $3, however with the exchange rate on the $AUS atm that would be like $US 400 or something. Works great.
the silicons can be hit and miss i find.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
