Chill
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Quick noob question [Vacuum Desiccation in Mason Jars]
Does vacuum sealed jars have any application in reagent storage? I store my KNO3 in a mason jar, and that made me think of this question. KNO3 is
slightly hydroscopic, so I wonder if vacuum sealing the container would limit the moisture that it could grab from the air. Is this a good idea?
What about other chemicals? Air sensitive or other hydroscopic reagents come to mind when I consider vacuum sealed mason jars. Would you guys suggest
sealing any chemicals, if so, which ones and why?
Thank you
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: appended
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[Edited on 6.8.13 by bfesser]
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bfesser
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<a href="viewthread.php?tid=11262">Related topic.</a>
I don't see the benefit of evacuating the jars which you're storing your reagents in, but I do like the idea of using <a
href="http://en.wikipedia.org/wiki/Mason_jar" target="_blank">Mason jars</a> <img src="../scipics/_wiki.png" /> as miniature vacuum
desiccators for drying products. You could simply fill the bottom with drying agent, and gently set a beaker of your wet product on top, then
evacuate and wait. I just might look into picking up one of those <a href="http://www.youtube.com/watch?v=lGfUwEf810g" target="_blank">vacuum
sealing </a> <img src="../scipics/_yt.png" /> adapters. I found one <a href="http://www.amazon.com/dp/B00005TN7H" target="_blank">
on Amazon</a> <img src="../scipics/_ext.png" /> for only ten bucks—not bad—but I bet the hardware store in my
neighborhood has them. Thanks for mentioning these, I had no idea they existed. Of course, if you already have a pressure cooker (or vacuum
chamber), you could just set the jars inside, and evacuate the whole thing.
[Edited on 31.7.13 by bfesser]
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Chill
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I've got an idea.
Silica gel is pretty cheap and reusable as a dessicant, right (put it in an oven to dry it)? I can cut up an old cotton shirt and make a pouch to hold
the silica crystals in, then drop the pouch in my jar to absorb moisture.
It should work as a desiccator jar, but a whole lot cheaper. I can still use a vacuum too, not that I would need to. What do you think?
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: removed
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Hey man, no problem. I had a hunch this would be a good idea, and i'm glad I got to spread my ideas, even though i'm pretty sure it's not an original
one.
I have to admit, I've never really looked into dessication before. When you want to dry a reagent, should you use a vacuum AND desiccant? After
drying, you should obviously store the reagent with some desiccant to KEEP it dry, correct?
My idea with the cotton pouch seems good for solids, but what about liquids? H2SO4 can get dilute pretty quick from moisture in the air, so how can
you store it with a desiccant on the cheap? I've heard of a "bag" method where you store the liquid and desiccant in a ziplock bag, but that would
mean leaving the liquid open and susceptible to spilling! Any ideas for liquids?
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: merged
sequential posts, removed unnecessary quote]
[Edited on 6.8.13 by bfesser]
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ElizabethGreene
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Chill: Wouldn't the acid sublimate and attack the enamel-over-steel lid and/or rubber gasket?
Thanks for the idea about the vacuum desiccator.
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watson.fawkes
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Quote: Originally posted by Chill  | | I wonder if vacuum sealing the container would limit the moisture that it could grab from the air. Is this a good idea? |
It'll be much less effective than you'd like. Putting a negative pressure across a seal is pretty much asking for it to fail
(quickly or slowly), unless the seal is specifically designed for it, which Mason jars really aren't. (Admittedly the develop a few psi negative
pressure when used for canning, but that's not the same as 15 psi atmosphere.) The lids on Mason jars are designed for single-use, which means that
the first time you break the seal, there's less likelihood that it'll seal correctly again.
If you want to store hygroscopic or moderately oxygen sensitive compounds, such as iron(II) salts, consider setting up a nitrogen purge system. You
still want a seal. You still want a pressure differential, but you want it positive, so that any gas flow through a leaky seal is directed outwards.
And you only need 1 psi or so for this, much less than for vacuum.
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Pulverulescent
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| Quote: | | Wouldn't the acid sublimate[sic] and attack the enamel-over-steel lid and/or rubber gasket? |
(sigh!) H2SO4 doesn't sublime or attack vitreous enamel!
Its effect on rubber is a very gradual embrittlement . . .
"I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones"
A Einstein
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ElizabethGreene
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Sublimate was the wrong word. I meant, "Won't the acid go directly into a vapor under reduced pressure ..." Derp derp.  Thanks for the call-out.
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Chill
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| Quote: Originally posted by ElizabethGreene | Sublimate was the wrong word. I meant, "Won't the acid go directly into a vapor under reduced pressure ..." Derp derp. Thanks for the call-out.
|
Sorry if I wasn't clear, but I was talking about having Sulfuric acid and a desiccant together without a vacuum. How could this be
accomplished without the risk of spilling due to an open vessel? Perhaps add the desiccant inside the vessel, but that wouldn't work because Sulfuric
acid could slosh around in its closed container and make contact with the desiccant. Any ideas?
| Quote: Originally posted by watson.fawkes |
If you want to store hygroscopic or moderately oxygen sensitive compounds, such as iron(II) salts, consider setting up a nitrogen purge system. You
still want a seal. You still want a pressure differential, but you want it positive, so that any gas flow through a leaky seal is directed outwards.
And you only need 1 psi or so for this, much less than for vacuum. |
It's a good suggestion, but it seems difficult to pull off. Admittedly, this is the first time I've heard of nitrogen purge systems, and they do seem
to be very effective, but it seems far fetched that this is something an amateur home chemist can pull off. I would be very grateful if you are able
to prove me wrong though, as this would be a revolutionary discovery for me personally. In the meantime, I'll have to stick to my poor-mans mason
jars.
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: merged
sequential posts]
[Edited on 3.8.13 by bfesser]
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Fantasma4500
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didnt know KNO3 was actually hygroscopic by any possible means..?
anyhow, if you want a really simple way to keep your reagents dry, be it NH4NO3 or KNO3 then you can cut the top of a bottle, fill in some CaCl2
anhydrous, ofcourse
put lid on the container and pretty much done
the more tight the lid will fit the better ofcourse, this might need to be changed due to moisture buildup
for smaller dessicant needs you can just pack some CaCl2 in tissue paper and wrap it tight, it will or should drag the moisture through the paper
CaCl2 decomposes at a relatively high temperature so it can with a large surface pan be dried very effectively and thrown back into storage, plus its
very cheap and readily available
you can recognize it by dissolving some suspected CaCl2 in water, then adding NaHCO3 or similar solution
it should form a white precipitate, if reacted with HCl and its soluble theres a great chance that it is CaCl2, as most insoluble carbonates have an
equally insoluble chloride
no need to make it all fancy if simple rough designs work (=
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watson.fawkes
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You mean "something that I
can pull off". Apparently I'll have to agree with that.
Such a project is mostly plumbing. It's not like compressed gases are anathema to amateurs; the prevalence of small oxy-acetylene rigs attests to
that. The bottle you'd use for nitrogen in a purge system is the same one you'd use for oxygen with a welding torch; the difference is that you use a
different tank valve. Those tanks are easy to find; even Harbor Freight is carrying them now. And you buy the gas at exactly the same suppliers that
you buy oxygen from.
Other parts include regulators, valves, and other assorted plumbing. It's not the cheapest thing in the world if you buy all the parts new at retail,
but it's not particularly difficult, either.
Whether it's cost-effective at a small scale is another issue entirely. Building a single-purpose system is likely not, but a generic manifold system
can be used for a number of purposes. For example, incorporating a vacuum pump and an argon tank would allow sealing of ampoules under inert gas. Add
a flow meter and it can provide a lab source of inert gas for air-sensitive reactions.
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ElizabethGreene
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Taking a segway off of liquified gases (not that they aren't cool; they certainly are!) I started an experiment tonight to gauge the efficacy of a
mason jar as a vacuum desiccator chamber.
It'll be a bit before I have results beyond "did not implode", but I wanted to say thanks again for the idea.
FYI: If you heat your drying agent (i.e. MgSO4) in an oven all day, it will probably be "hot" when you start loading up the drying tubes.
That seems obvious now, but I still have a pair* of blisters from picking up the watch glass/baking dish.
* - Data gathered twice. Not for repeatability, just stupidity. 
Elizabeth
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Chill
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| Quote: Originally posted by ElizabethGreene |
FYI: If you heat your drying agent (i.e. MgSO4) in an oven all day, it will probably be "hot" when you start loading up the drying tubes.
That seems obvious now, but I still have a pair* of blisters from picking up the watch glass/baking dish.
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Ouch!
I'm curious why you chose magnesium sulfate as a desiccant. Silica gel is very easy to get a hold of and it works wonders. Is there any specific
reason?
I appreciate your effort for testing my idea. I'll be looking forward to the results.
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bfesser
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The capacity of the desiccant is a factor (how much moisture is captured per unit of desiccant), as well as the strength of absorption/adsorption (how
dry you can get the atmosphere) and chemical compatibility (reactivity with vapor/liquid).
<a href="http://www.sorbentsystems.com/desiccants_charts.html" target="_blank">Desiccant Chart Comparisons</a> <img
src="../scipics/_ext.png" /> — SorbentSystems.com
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Chill
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Not to get sidetracked, but I found that website before posting my comment. It doesn't mention magnesium sulfate as a desiccant so I decided to ask
ElizebethGreene with the hope that she could shed some light on it's properties compared to silica gel.
Turns out, magnesium sulfate is pretty easy to get (and cheap!) as epsom salt, so that's a plus. But I'd still prefer to pay a little more and get a
pound of rechargeable silica gel.
I managed to dig up some information myself from what seems to be Rochester university. A document labeled "Desiccant Selector Chart" indicates silica
gel as being more effective than magnesium sulfate. Also, interestingly, the chart says that magnesium sulfate is not "rechargeable". Wouldn't this
mean you can't dry it in the oven? This makes me question the document's validity considering I have Googled guides that successfully dry hydrated
magnesium sulfate (epsom salt).
Here is a link to the document to see for yourself.
[Edited on 8/6/2013 by Chill]
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Bot0nist
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I dehydrate epsom salts all the time, and calcium chloride, both in the oven. They both work as dessicants...
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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ElizabethGreene
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I have MgSO4 and NaOH as drying agents. The CVS Epsom salts are significantly cheaper than the drain cleaner. Recharging the
MgSO4 is pretty easy. The Merk index says it loses the last water of hydration at 250c. This is just beyond the uppermost range of my
thrift-store toaster oven, but easily reachable by a wall oven.
You have a couple of options for dehydrating it.
Method 1:
Heat in oven to 250c.
Grind the resulting lumps to powder.
Explanation: Heating the substance too quickly causes the un-decomposed crystals to melt. This leaves lumps. They eventually decompose, but you have
to grind them up when you are done.
Method 2:
Heat to 120c.
Wait a bit.
Heat to 250c.
"Crystals" fall apart with agitation, no grinding required.
Explanation: Heating the crystals slowly allows them not to melt, and they fall apart into the powder.
(Source: an older SM post I can't find now.)
There is an associated color change: the substance goes from a colorless translucent crystals to an opaque bright white crystal then powder. It
becomes significantly "fluffier" and the mass decreases from the water lost to the atmosphere. (Source: Direct observation, unrepeated)
If you track the loss in mass from heating you can math out the average hydration state of your end product. Work fast, because it will absorb water
from the air while you are mathing.
Finally, it's hot. Don't try to pick up your baking dish bare-handed.
Chill: That chart specifically relates to removing water from a solution in organic chemistry. That's different from using it as a drying agent in a
desiccator chamber like a mason jar or Zip-loc baggie. Here is an example.
Limonene is the essential oil from orange peels or lemons. To extract it, you steam distill the peels. This gives you a mixture of oil and water.
This mixture goes into a separatory funnel and (hopefully!) the water and oil layers separate. Then you drain off the oil layer. This oil layer is
"mostly" oil, but still contains a little bit of water. That little bit of water can interfere with some future reactions, so you have to get rid of
it. To "Dry" the oil, you add a drying agent like MgSO4. This grabs the last little bit of water out leaving you with a dry solution.
The drying agent is then removed by filtration. You could wash and re-use it at this point, but why would you? It is so much cheaper than the other
alternatives, there is very little reason to risk contaminating a future batch.
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bfesser
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| Quote: Originally posted by ElizabethGreene | There is an associated color change: the substance goes from a colorless translucent crystals to an opaque bright white crystal then powder. It
becomes significantly "fluffier" and the mass decreases from the water lost to the atmosphere. (Source: Direct observation, unrepeated)
If you track the loss in mass from heating you can math out the average hydration state of your end product. Work fast, because it will absorb water
from the air while you are mathing. |
I can independently confirm your observation; I have seen this many
times. I've also determined the <a href="http://en.wikipedia.org/wiki/Water_of_crystallization" target="_blank">water of hydration</a>
<img src="../scipics/_wiki.png" />, as you have suggested. It makes for a great beginners' experiment in Analytical Chemistry, as well as
providing a useful product. I also advocate picking up a cheap toaster oven. I've used mine to re-activate desiccants, as well as to dry small
glassware after cleaning. They usually come with a small baking pan when new, and this can be used as a tray to spread out the desiccant for drying
(enamel is fine; watch out for corrosion with aluminium, though). | Quote: Originally posted by bfesser | | I just might look into picking up one of those vacuum sealing adapters . . . I bet the hardware store in my neighborhood has them.
|
Disappointingly, they didn't—despite a well stocked canning section (Frattallone's Ace Hardware on
Grand & Cambridge, St. Paul).
[edit] After searching online and calling around, <a href="http://www.fleetfarm.com/detail/foodsaver-wide-mouth-jar-sealer/0000000013412"
target="_blank">Mills <em>Fleet</em> Farm<sup>®</sup></a> <img src="../scipics/_ext.png" /> is the
first place I've found in my area (Twin Cities, MN) to carry this thing (<a href="http://www.foodsaver.com/product.aspx?pid=9066"
target="_blank">FoodSaver<sup>®</sup> Wide-Mouth Jar Sealer</a> <img src="../scipics/_ext.png" /> . I couldn't even find the "regular" one. Stores I checked that don't carry either;
Bed Bath & Beyond<sup>®</sup>, Menards<sup>®</sup>, Target<sup>®</sup>,
<em>Ace<sup>®</sup></em> Hardware, Egg|Plant Urban Farm Supply, Kitchen Window, Kohl's<sup>®</sup>
(Wide-Mouth, online only), Wal-Mart.
[2nd edit] I forgot to note that in my research I found that the regular Mason Jars may hold a vacuum better than the wide-mouth version (<a
href="http://www.homesteadingtoday.com/country-homemaking/preserving-harvest/365777-regular-vs-wide-mouth-jars.html"
target="_blank">source</a> <img src="../scipics/_ext.png" />.
[Edited on 6.8.13 by bfesser]
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ElizabethGreene
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Oh for goodness sake, don't buy a toaster oven new.. Mine was $4.00 at the Goodwill store (a thrift shop). It's a stainless steel Kruup model too.
If you have a FoodSaver, I've heard anecdotes that you can use the accessory hose to suck the air out of a pressure cooker for a larger vacuum
chamber. If you have the bits already it is worth trying.
Inquiry: will auto Vacuum hoses hold up to a "real" Vacuum, i.e. that produced by a refrigerator compressor in good repair?
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ElectroWin
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as an aside,
I've been storing my (mostly anhydrous) CaCl2 in bowls sealed with cling wrap for about a year, with no visible change.
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ElizabethGreene
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BFesser:
I actually don't have a "Mason Jar adapter". I have one of these
FoodSaver ¾ Quart Canister (4" x 5 7/8"). * Note, mine may not be that precise one. I'm much to lazy to measure at this moment. Mine is big
enough for pint jars, but not quarts. I can vacuum both wide mouth or standard jars. I drop the mason jar with the lid on and a band very loosely
screwed on. The purpose of the band is to keep the lid from moving out of position during sealing and to provide something to grab to retrieve the
jar. Atmospheric pressure holds the lid in place tightly when the vacuum is released from the container.
Another advantage of this approach is that the jar is in an enclosed container if it implodes upon exposure to atmosphere.
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Chill
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I'm a little surprised by your concern over the fortitude of mason jars. I've never heard of mason jars imploding when letting atmosphere back in.
Then again, people who can food don't usually use super high vacuum. I don't suppose you can test the strength of the vacuum you applied to your jar
to get a starting point for what these jars can hold?
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bfesser
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I'd be more concerned with the strength of the lid than the glass. When I get one of those adapters, I'll hook it up to my rotary-vane pump and do
<a href="https://www.youtube.com/watch?v=qHMQxqVFOgc" target="_blank">reliability testing</a> <img src="../scipics/_yt.png" />.
[Edited on 7.8.13 by bfesser]
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bfesser
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Thread Moved
11-8-2013 at 07:56 |
ElizabethGreene
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Experimental results: I found no significant difference between the rate of dessication in a foodsaver vacuum sealed mason jar vs. a
jar sealed at ambient pressure. This experiment may be flawed though, and should be repeated under slightly different conditions.
Procedure: A water and food coloring solution was prepared and 20mL dispensed into each of three mason jars. A test tube containing
10 grams of hot (~500 F) Magnesium Sulfate was added to each jar. One jar was lidded and vacuum sealed with the foodsaver. One jar was lidded and
sealed at ambient pressure. The final jar was covered with a coffee filter held in place by a jar band. All three were placed in a
non-climate-controlled garage. To collect evaporation data, the height of the liquid level was measured by placing a ruler next to each jar and
photographing it. The margin of error is estimated at +/- 1 mm.
The initial height of each column was 16mm. The fluid levels in each jar decreased at approximately the same rate until day 5. After day 5, the
fluid levels in the vacuum and ambient jars remained the same, 11 mm. The coffee-filter-covered jar continued to evaporate until the termination of
the experiment on day 20.
Discussion:
I believe the desiccant saturated at day 5, and the subsequent level drop in the coffee-filter jar was evaporation to the atmosphere. Hypothetically,
the rate of dessication in the sealed jars should be a function of two parameters. The first being the "evaporation rate" or (lacking the proper word
here) spontaneous solubility of the liquid in the air. As I understand it the principal behind vacuum desiccators is that this value increases as the
inverse of atmospheric pressure.
The second parameter is the "absorption rate" of the desiccant. In my case I had test tubes full of the desiccant, presenting a relatively small
amount of the surface area to the atmosphere inside the jar. I think this artificially limited this second parameter and caused the unexpected
results in this experiment.
Future work: I'd like to test this surface-area as a limiting factor idea by repeating the experiment and radically increasing the
available surface area of the desiccant using cloth or paper sachets. I would also add another coffee-filter-lidded jar with no desiccant to see if
the MgSO4 is making a difference in the evaporation rate.
Self-Criticism: I should have measured and recorded the volume of liquid remaining in each jar at the end of the experiment. I will
do so on Saturday.
Note: This series of experiments is literally as exciting as watching paint dry.
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zenosx
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The KNO3 I had stored in mason jars eventually attacked the lid enough to have it fall apart upon opening. I have better bottles now though this was
over 70% dilute.
I love the desiccator idea, I am going to have to give this a go. Using an old pressure cooker also sounds great...
A question that sometimes drives me hazy: am I or are the others crazy?
Albert Einstein
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bfesser
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I assume you mean HNO<sub>3</sub>?
I picked up one of the jar sealers, but have yet to epoxy a hose barb to it.
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