Poppy
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Incredible evaporation of salted water
For the sake of curiosity, and to bring up some notion on how much salt actually evaporates along with water in coastal areas I have been inclined to
share the witness of the event which was experimented today. Remember that college trick of producing salt in air by mixing ammonia and hydrochloric
acid vapours in air and watching a beatiful myst forming? Ok, thats nothing special, as everyone knows the NH3 gas is reacting directly with HCl to
produce ammonium chloride particles which are dispersed through the air. But in an another demonstration, a similar situation is mimitized on
different conditions: no reaction is occuring but simply a physical phenomenon. It consists on observing the salt, ammonium chloride in this case,
being carried by the molecules of water vapour. On pouring a hot neutral solution of NH4Cl unto another vessel one can tell that very myst identical
to NH4Cl when NH3 reacts with acid vapours in air, except now the water vapours, as they leave the contair, carry some salt with then up to a certain
saturation, and, as they cool and disperse as air humidity they leave behind the salt, showing again that cool effect.
So if a friend of yours tell the trick is over, you can show yourself prepared to "recycle" the cenario by doing this !! 
Also, it is an interesting demonstration of gas phase precipitation, whose current uses I might not inquiry.
NOTE: the solution was in fact at pH 8, for those who might check on it, furthermore ammonia might well play a role on the show.
Sorry for not having pics, we might try this another time and pick some.
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bfesser
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Thread Moved
4-1-2014 at 17:50 |
Poppy
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Sorry for replying to my own post, but recently, in the attempt to dry an ammonium chloride sample, it smoked a lot filling the entire house with a
dusty smell. Whats the matter with all this smoking? Any of you have an expertise to share on this matter??
Because hopefully I was inhaling equimolar quantities of both NH3 and HCl, so it should be ok. at elast I guess.
Please?
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papaya
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Nothing wrong with it, and it's not an "evaporation" of salt, it's the reversible reaction between ammonia and acid that causes this phenomenon: on
heating NH4Cl partially decomposes to NH3 and HCL, which will combine again on cold to form a salt. It's commonly misunderstood btw., many think that
the salt sublimes, while the process is chemical in fact (as I read somewhere, don't ask for the refs. now).
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papaya
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Quote: Originally posted by papaya  | | Nothing wrong with it, and it's not an "evaporation" of salt, it's the reversible reaction between ammonia and acid that causes this phenomenon: on
heating NH4Cl partially decomposes to NH3 and HCL, which will combine again on cold to form a salt. It's commonly misunderstood btw., many think that
the salt sublimes, while the process is chemical in fact (as I read somewhere, don't ask for the refs. now). |
Also if NH4CL is added to some type of hot pyrotechnical mixture it'll make an effective smoke, anybody tried to mix it with thermite ? 
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blogfast25
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| Quote: Originally posted by papaya | | Also if NH4CL is added to some type of hot pyrotechnical mixture it'll make an effective smoke, anybody tried to mix it with thermite ? |
In KClO3 boosted thermites (e.g. TiO2) the KCl by-product 'boils' off. It makes those thermites quite smoky (white smoke).
Adding something volatile like NH4Cl should have a similar effect. I'd warn against using too large amounts because it could lead to
deflagration of the thermite mixture, causing to material being thrown out of the crucible.
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bfesser
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| Quote: Originally posted by Poppy | For the sake of curiosity, and to bring up some notion on how much salt actually evaporates along with water in coastal areas I have been inclined to
share the witness of the event which was experimented today.
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An interesting way of writing this, but alright. The salt doesn't evaporate along with the water, it forms
<a href="http://en.wikipedia.org/wiki/Aerosol" target="_blank">aerosols</a> <img src="../scipics/_wiki.png" /> by the action of wind
and waves forming spray from which the water evaporates.<a href="http://en.wikipedia.org/wiki/Sea_spray" target="_blank"> | Quote: | | Salt spray contains a high concentration of mineral salts, particularly chloride ions. . . . Salts do not dissolve in air directly, but are suspended
as fine particulates, or dissolved in microscopic airborne water droplets. <img src="../scipics/_wiki.png" /> |
</a>
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Morgan
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I wonder if ammonium chloride would add any to the fog or mist effect of an ultrasonic transducer or to what extent the salt would be lifted into the
air along with the water? I bought one of these small devices that makes a bowl of mist along with colored LED lights that change color. I purchased a
new one the other day from a junk store with the Discovery Channel name on the box. You can add fragrances or even lemon juice it said to the water
for added effect.
Anyway, it's remarkable how sudden the effect starts up, instant fog the very second the thing is turned on. I put my finger about 3 cm away from the
transducer and quickly felt a kind of burning pain. The directions said to use tap water for best results and not distilled water.
Here's a multi-element one for illustration. Note how fast it starts up, as/after the light turns on.
http://www.youtube.com/watch?v=TJi9qvlk9cs
I culled a few comments from this plant forum, although I don't know much about ultrasonic transducers to say what's what. But they seem like
something fun to play with.
"Ultrasonic humidifiers use a piezo-electric transducer to create a high frequency mechanical oscillation in a body of water. The water tries to
follow the high frequency oscillation but cannot because of its comparative weight and mass inertia. Thus, a momentary vacuum is created on the
negative oscillation, causing the water to cavitate into vapor. The transducer follows this with a positive oscillation that creates high pressure
compression waves on the water's surface, releasing tiny vapor molecules of water into the air. This is an extremely fine mist, about one micron in
diameter, that is quickly absorbed into the air flow. Since the mist is created by oscillation, not heat, the water temperature need not be raised.
Ultrasonic humidifiers, therefore, can create instantaneous humidity, and don't have to wait for a heating element to boil the water. This precise
on/off humidity control is the hallmark of ultrasonic humidifiers. In addition, unlike wet pad humidifiers, ultrasonic units can be of comparatively
small size, and still produce significant amounts of vapor.
"My guess is that the dissolved solids form a seed that the vapor molecules condense around to the point that you can see the vapor. Easy enough to
test with either a hygrometer or see if the water supply in the reservoir is consumed faster than by simple evaporation."
"Of course you could always charge the vapor particles so that the repel each other and won't condense as easily. A method developed for dispersing
chemical and biological agents."
"A major health problem with ultrasonic humidifiers is that some bacteria in the water also gets dispersed along with the water vapor. So some
undissolved particles would also get dispersed."
http://www.terraforums.com/forums/archive/index.php/t-120082...
[Edited on 6-1-2014 by Morgan]
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Poppy
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| Quote: Originally posted by bfesser |
An interesting way of writing this, but alright. The salt doesn't evaporate along with the water, it forms <a
href="http://en.wikipedia.org/wiki/Aerosol" target="_blank">aerosols</a> <img src="../scipics/_wiki.png" /> by the action of wind and
waves forming spray from which the water evaporates.<a href="http://en.wikipedia.org/wiki/Sea_spray" target="_blank"> | Quote: | | Salt spray contains a high concentration of mineral salts, particularly chloride ions. . . . Salts do not dissolve in air directly, but are suspended
as fine particulates, or dissolved in microscopic airborne water droplets. <img src="../scipics/_wiki.png" /> |
</a> |
I always had a trip on aerosols. Wiki says dust and clouds are solid particles in suspension, so I wonder if one could shake the particles to an
extent such that a discharge could occur between two points of the aerosol mass.
Morgan,
that humidifier is crazy but hey, look around at those mysts you may tell NH4Cl lasts much longer than that. Smoke bombs are the
kind of thing which mostly resembles the mess caused by ammonium chloride.
http://www.youtube.com/watch?v=PzS0BtsthEU
A kind of sonic trap would probably trap the myst such as subatomic charges are trapped in physics experiments, on a counter to the property they have
to stick to the things they touch.
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Morgan
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It might be interesting to see if ammonium chloride aerosols would be good at generating static electricity in air.
Poppy, speaking of smoke bombs, when I was about 12 years old I lit the large size coffee can full of KNO3 and sugar. The long, tall cloud of smoke it
made worried me quite a bit because it lingered for a long time high in the sky above my house. I thought the police might come, the grandeur of the
cloud looked so out of place.
The Amazing Power of Static Electricity
http://www.youtube.com/watch?v=2sSqzLPMb4s#t=12m29s
"From the experiments we were able to conclude there is defi nite charging of these aerosols. Observing that rubbed glass will attract the NH3HCl
microtornado and deflect the NH4NO3 microtornado the charges are negative and positive respectively."
http://www.math.colostate.edu/~shipman/47/volume5a2013/MATH4...
[Edited on 7-1-2014 by Morgan]
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phlogiston
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| Quote: Originally posted by blogfast25 |
In KClO3 boosted thermites (e.g. TiO2) the KCl by-product 'boils' off. It makes those thermites quite smoky (white smoke).
Adding something volatile like NH4Cl should have a similar effect. I'd warn against using too large amounts because it could lead to
deflagration of the thermite mixture, causing to material being thrown out of the crucible. |
Pyrotechnic mixtures containing KClO<sub>3</sub> and NH<sub>4</sub>Cl or any other ammonium salt should not be stored for any
length of time, because ammonium chlorate may form (especially when moisture is present), which is known to spontaneously ignite upon storage.
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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Poppy
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Unless the salt powders are properly coated which might lead to pellets of a sintered material much like vitamin C nutritional supplement capsules.
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