Chemistry students, please help!

[Jonluw]

Hiya escapists chemistry students.

I want to make myself some sodium acetate, so I've gotten a hold of some vinegar and NaOH (because lye is a good deal more awesome than baking soda).

In any case, from what I understand, the reaction that creates sodium acetate is spontaneous, so creating it should be as easy as mixing vinegar and lye.
However, my vinegar is very weak. Like 7% concentration weak. I did the maths, and if I'm not wrong (I am admittedly a bit rusty), it should be a 1,2 molar solution.
Unfortunately, I didn't have a weight to weigh up the 8-10 grams of NaOH I figured I'd need to mix with the 200 ml of vinegar I'd measured up, so I sort of used my gut feeling when adding the lye.

In any case, there's a lot of water in this solution now, and I need to evaporate it to get a hold of my precious crystals. Sadly, all I have access to is kitchen equipment (no microwave).

What I've done is gone ahead and used a cast-iron frying pan for heating my solution.
What I'd like to know is this:
Will this frying pan be safe for making regular food again after I'm done with it?

 

[ICantBelieveItGoesBoom]

You shouldn't need to heat up the solution very much and in fact it is better to simply leave the solution in a warm area, and let the crystals form over a few days as this will create the most Sodium Acetate for what you added.

Out of interest, what is it that made you suddenly want to make some sodium acetate?

EDIT: Also, it would be a good idea to put something over the container for the solution so stuff doesn't fall into it while its evaporating, in a lab you'd use an upturned funnel but with what you have in the kitchen maybe a colander will do?

 

[LetalisK]

Silly Jonluw, this is why you need a dedicated meth pan.

Seriously though, I don't know chemistry, but I do know the Googles, and it would appear you're fine.

http://www.castironcollector.com/cleaning.php

 

[Jonluw]

You shouldn't need to heat up the solution very much and in fact it is better to simply leave the solution in a warm area, and let the crystals form over a few days as this will create the most Sodium Acetate for what you added.

I am pathologically impatient and I don't think it's safe to have chemicals standing around the dorm for days at a time.
It's sort of the same reason why I'm not using baking soda. If I have two options, I'm nearly always going to go with the one with more "explosion potential" as I call it.

Oh yeah, I should probably mention: I'm doing this with the dorm's shared frying pan.
Turned out it was dirty as shit. The resulting crystals (if that is really what it ended up being. I'm afraid it might just be fat) were brown.

Out of interest, what is it that made you suddenly want to make some sodium acetate?

I was thinking about that liquid in heating packs and how it's really awesome and how I'd like to have some of it lying around right about now; so I googled it and found it was called sodium acetate. This made me stop and wonder "shouldn't I be able to synthezise that in our kitchen pretty easily?"

And thus I decided to go buy lye and vinegar.

But the experiment was pretty much a failure. I guess I'll just buy some sodium acetate off the net and go play with lye and aluminum foil instead.
I just need to clean the frying pan first.

 

[Pinkamena]

Experimenting in the kitchen, huh? You and I have at least something in common it seems. And I think you'd be better off just buying some of it off the net.

 

[Launcelot111]

Umm, Avogadro's number? My chemistry is rusty.

Anyway, a quick google search suggests that mixing vinegar and cast iron is a no-no. I'd assume that further chemistry applications would fall under the same advice

EDIT: Now I'm reading more articles and they say that both vinegar and lye are good for cleaning cast iron. I think what they're saying is that if you have all the stuff built onto the cast iron like you're supposed to, then the vinegar won't do anything to that, but if your acids are touching the actual iron, you could be doing some damage. I dunno, you should probably ask someone else

 

[Esotera]

There are ways to increase concentration of solutions but it's generally a lot harder than diluting them. However, a quick consultation shows that acetate has a higher boiling point than water, so if you were careful to keep it at around 100C, you could potentially boil off most of the water & get a much higher concentration.

As for the moles, it doesn't really matter what the concentration is. Just add way more vinegar than NaOH & it will be in excess, meaning you push the reaction in the right direction.

Also it's probably not a good idea to grow crystals if you're impatient - leave it for a couple of days in a warm area & you'll get some massive ones.

edit:

The amounts you put in sound about right, but try and find some spare glassware, maybe a pyrex cooking dish? And you shouldn't be eating/drinking out of anything you use in the lab, that's just common sense...don't do it on the cheap.

 

[Atrocious Joystick]

I'm no cook so I don't know if there is any general no-no's involved with those particular ingredients and a frying pan. But Sodium Acetate is a food additive, it is for example the "salt and vinegar" taste in salt and vinegars chips. So it should be safe to use that frying pan again. You might want to clean it and not chug-a-lug the sodium acetate but it won't harm you should you accidentally get some on your stake later.

 

[Jonluw]

There are ways to increase concentration of solutions but it's generally a lot harder than diluting them. However, a quick consultation shows that acetate has a higher boiling point than water, so if you were careful to keep it at around 100C, you could potentially boil off most of the water & get a much higher concentration.

As for the moles, it doesn't really matter what the concentration is. Just add way more vinegar than NaOH & it will be in excess, meaning you push the reaction in the right direction.

Also it's probably not a good idea to grow crystals if you're impatient - leave it for a couple of days in a warm area & you'll get some massive ones.

edit:

The amounts you put in sound about right, but try and find some spare glassware, maybe a pyrex cooking dish? And you shouldn't be eating/drinking out of anything you use in the lab, that's just common sense...don't do it on the cheap.

Something interesting just happened:

I left the used and washed frying pan lying in the cupboard with one of our aluminum frying pans. The frying pan had a strange silvery coating when I removed it from the cupboard...

And just now I made the silly decision of warming a piece of aluminum foil in the same frying pan in order to purify the crystals. The frying pan now has a nice new coat of rust.

Edit: And I'm not using the frying pan in the lab. I'm labbing in the frying pan.
Plus, the chemicals I'm dealing with are respectively cleaning agents of frying pans and a food additive so I didn't consider it very dangerous exactly.

 

[Esotera]

Something interesting just happened:

I left the used and washed frying pan lying in the cupboard with one of our aluminum frying pans. The frying pan had a strange silvery coating when I removed it from the cupboard...

And just now I made the silly decision of warming a piece of aluminum foil in the same frying pan in order to purify the crystals. The frying pan now has a nice new coat of rust.

Edit: And I'm not using the frying pan in the lab. I'm labbing in the frying pan.
Plus, the chemicals I'm dealing with are respectively cleaning agents of frying pans and a food additive so I didn't consider it very dangerous exactly.

My main concern (and why I put a disclaimer) is that you don't know what chemicals are going to be present in the frying pan, and how they'll react with whatever you're making. Acetate & NaOH are harmless by themselves but there's always the chance you'll get some funny reaction with some complex chemical in the frying pan.

Not really sure why it's rusted either, although I'm sure someone who's actually done chemistry recently can reveal the reason...

 

[MsWhatsit]

When you used lye in the cast-iron pan, you probably stripped the seasoning off the pan. Lye (in the form of oven cleaner) is a very commonly-suggested way to strip cast-iron pans for the purpose of reseasoning. A cast-iron pan that has been stripped of seasoning is very susceptible to rust.

You probably need to reseason the pan. The Internet has a million theories on how to do this, but my favorite is here: http://sherylcanter.com/wordpress/2010/01/a-science-based-technique-for-seasoning-cast-iron/

You can absolutely use the pan for regular cooking after you're done. You could now, if it weren't for the possibility of getting rust in your food.

 

[BlackStar42]

Sodium acetate is quite soluble in water, so you should be able to wash the pan and get rid of any remaining traces. If you want to purify your crystals I'd recommend recrystallising them in ethanol.

 

[thiosk]

There are ways to increase concentration of solutions but it's generally a lot harder than diluting them. However, a quick consultation shows that acetate has a higher boiling point than water, so if you were careful to keep it at around 100C, you could potentially boil off most of the water & get a much higher concentration.

As for the moles, it doesn't really matter what the concentration is. Just add way more vinegar than NaOH & it will be in excess, meaning you push the reaction in the right direction.

Also it's probably not a good idea to grow crystals if you're impatient - leave it for a couple of days in a warm area & you'll get some massive ones.

edit:

The amounts you put in sound about right, but try and find some spare glassware, maybe a pyrex cooking dish? And you shouldn't be eating/drinking out of anything you use in the lab, that's just common sense...don't do it on the cheap.

Something interesting just happened:

I left the used and washed frying pan lying in the cupboard with one of our aluminum frying pans. The frying pan had a strange silvery coating when I removed it from the cupboard...

And just now I made the silly decision of warming a piece of aluminum foil in the same frying pan in order to purify the crystals. The frying pan now has a nice new coat of rust.

Edit: And I'm not using the frying pan in the lab. I'm labbing in the frying pan.
Plus, the chemicals I'm dealing with are respectively cleaning agents of frying pans and a food additive so I didn't consider it very dangerous exactly.

This is likely an electrochemical reaction between a steel fastener on the pan and the al foil in the salty solution. The aluminum pan is coated with a thick oxide to prevent that reaction. If you put tomato sauce in an iron pan and cover it with foil, such that the foil touches sauce and pan, you get the same reaction. It's a simple battery.

Take the vinegar and add baking sofa. Refrigerate. I've read 4 tablespoons to 1 liter.

The solubility should drop enough to drop out the crystals. Filter and dry.

 

[Jonluw]

Something interesting just happened:

I left the used and washed frying pan lying in the cupboard with one of our aluminum frying pans. The frying pan had a strange silvery coating when I removed it from the cupboard...

And just now I made the silly decision of warming a piece of aluminum foil in the same frying pan in order to purify the crystals. The frying pan now has a nice new coat of rust.

Edit: And I'm not using the frying pan in the lab. I'm labbing in the frying pan.
Plus, the chemicals I'm dealing with are respectively cleaning agents of frying pans and a food additive so I didn't consider it very dangerous exactly.

This is likely an electrochemical reaction between a steel fastener on the pan and the al foil in the salty solution. The aluminum pan is coated with a thick oxide to prevent that reaction. If you put tomato sauce in an iron pan and cover it with foil, such that the foil touches sauce and pan, you get the same reaction. It's a simple battery.

Are you talking about the reaction that left the silvery coating, or the one that made the pan rust?

Take the vinegar and add baking sofa. Refrigerate. I've read 4 tablespoons to 1 liter.

Surely that would depend on the molarity of the vinegar, no?
I'm using very approxiate amounts right now, but I've just left out a sample for evaporation.

 

[thiosk]

Are you talking about the reaction that left the silvery coating, or the one that made the pan rust?

Take the vinegar and add baking sofa. Refrigerate. I've read 4 tablespoons to 1 liter.

Surely that would depend on the molarity of the vinegar, no?
I'm using very approxiate amounts right now, but I've just left out a sample for evaporation.

I hadn't carefully read the section on the silvery coating.

However, you mentioned aluminum pan, and aluminum does not rust in the same way as iron and steel, and is certainly not red, which is what I assumed from the description.

However, I did leave off an important step in my rush (the ipad window closed like five times on my response!)

Before refrigeration, boil off most of the liquid from the above reaction. Go to about 10% original volume, but DO NOT dry it out.

The hot solution that is left should be supersaturated with acetate. I think any typical commercial white vinegar solutions will suffice.

 

[Jonluw]

Are you talking about the reaction that left the silvery coating, or the one that made the pan rust?

Take the vinegar and add baking sofa. Refrigerate. I've read 4 tablespoons to 1 liter.

Surely that would depend on the molarity of the vinegar, no?
I'm using very approxiate amounts right now, but I've just left out a sample for evaporation.

I hadn't carefully read the section on the silvery coating.

However, you mentioned aluminum pan, and aluminum does not rust in the same way as iron and steel, and is certainly not red, which is what I assumed from the description.

Yeah, nothing visible happened to the aluminum pan, but the iron pan got a silvery coating, and after that started rusting when I heated some aluminum foil in it.

However, I did leave off an important step in my rush (the ipad window closed like five times on my response!)

Before refrigeration, boil off most of the liquid from the above reaction. Go to about 10% original volume, but DO NOT dry it out.

The hot solution that is left should be supersaturated with acetate. I think any typical commercial white vinegar solutions will suffice.

This is what I've been trying to do all along.
However, it's difficult to do with kitchen appliances:
I can't use an aluminum pot or pan due to the nature of the chemicals, and the iron pan was seasoned so boiling my solution in that left me with a ruined pan and brown crystals.

I tried to heat a new batch in a glass soda bottle, but it cracked and spilled the stuff on my counter. Luckily I managed to save most of it, which I've now left in a plastic bottle to just evaporate on its own.

 

[Jonluw]

When you used lye in the cast-iron pan, you probably stripped the seasoning off the pan. Lye (in the form of oven cleaner) is a very commonly-suggested way to strip cast-iron pans for the purpose of reseasoning. A cast-iron pan that has been stripped of seasoning is very susceptible to rust.

You probably need to reseason the pan. The Internet has a million theories on how to do this, but my favorite is here: http://sherylcanter.com/wordpress/2010/01/a-science-based-technique-for-seasoning-cast-iron/

You can absolutely use the pan for regular cooking after you're done. You could now, if it weren't for the possibility of getting rust in your food.

Thanks.
Reseasoning sounds like a royal pain though. Might just be more convenient to buy a new one, considering that the wooden handle on this one is already loose anyways.

 

[TAdamson]

Why would you use lye NaOH when sodium bicarbonate would be fine and far safer

Baking soda is also better from a residue point of view but as long as you scrub the pan with some vinegar after using lye you should be fine... Unless the lye destroys your pan.

Sodium hydroxide also eats away at glass so don't.... But you already did....

 

[Evil Smurf]

Silly Jonluw, this is why you need a dedicated meth pan.

I make my meth in an electric frying pan, it's a portable meth lab!

Want meth?
http://global.fncstatic.com/static/managed/img/Leisure/breakingbad_blueglass.jpg

Why did you want to do this anyway?

 

[Jonluw]

Why would you use lye NaOH when sodium bicarbonate would be fine and far safer.

Because if I'm going to spend money on buyig either lye or baking soda, it's in my nature to buy the more reactive chemical. That way I can spend the leftovers on making hydrogen.