Aici am postat ceva interesant ce am gasit pe internet(ca majoriatea aricolelor). Mai intai va recomand sa veteti despre ce e vorba uitandu-va la filmuletul urmator. http://www.youtube.com/watch?v=aC-KOYQsIvU
Acetatul de sodiu il puteti cumpara de pe internet, sau puteti incerca sa il creeati acasa urmarind cei 10 pasi simpli de mai jos. Trebuie doar sa aveti putina rabdare si sa stiti putina engleza.
Intro
If you've ever wanted to play around with sodium acetate, but you're too much of a nerd to simply go online and buy some from a chemical supply house - noooo, that'd be too easy, you want to make it, from scratch - then this instructable is for you.
Inside, I show the whole process, from baking soda and vinegar, through concentration and filtering, to final crystallization.
(Please note that you, not I, explicitly assume all risk associated with playing with chemicals, fire, or hot things. Use common sense. If you're not an adult, enlist the help of a parent. If you're an idiot, close your browser now before you burn yourself. And regardless, by reading any of the suggestions contained herein, you implicitly assume full responsibility for any and all accidents, burns, lacerations, ruptured spleens, loss of consciousness, death, shin splints, hangovers, spurned advances, or insolvency that may result. Seriously... use your brain.)
Acetatul de sodiu il puteti cumpara de pe internet, sau puteti incerca sa il creeati acasa urmarind cei 10 pasi simpli de mai jos. Trebuie doar sa aveti putina rabdare si sa stiti putina engleza.
Intro
If you've ever wanted to play around with sodium acetate, but you're too much of a nerd to simply go online and buy some from a chemical supply house - noooo, that'd be too easy, you want to make it, from scratch - then this instructable is for you.
Inside, I show the whole process, from baking soda and vinegar, through concentration and filtering, to final crystallization.
(Please note that you, not I, explicitly assume all risk associated with playing with chemicals, fire, or hot things. Use common sense. If you're not an adult, enlist the help of a parent. If you're an idiot, close your browser now before you burn yourself. And regardless, by reading any of the suggestions contained herein, you implicitly assume full responsibility for any and all accidents, burns, lacerations, ruptured spleens, loss of consciousness, death, shin splints, hangovers, spurned advances, or insolvency that may result. Seriously... use your brain.)
Step 1 Preparation
We'll be making approximately 330 mL (or 11 fl oz) of supersaturated solution.
You will need the following items:
- One 16 oz box of baking soda (sodium bicarbonate)
- One gallon jug of distilled white vinegar (acetic acid)
- Clean pot for boiling (5.5 Qt or larger)
- Another clean pot for filtering (4 Qt or larger)
- Pack of coffee filters (basket style, not funnel shaped)
- Small wire mesh strainer (big enough to hold a coffee filter)
- One cup measuring cup for pouring hot solution through filter
- Large clean cooking spoon for removing samples while boiling
- Small clean dark dish (e.g. custard cup) for holding samples
- Clean jar to hold final solution
Step 2 Combining baking soda with vinegar
Start by pouring all but one cup of the white vinegar into the boiling container (5.5 Qt or larger). (See note about acids below...)
Then, carefully add baking soda to the vinegar, small amounts at a time (no more than a tablespoon). Sprinkle it over the vinegar - don't just dump it in. If you add too much baking soda too quickly, the foam from the reaction may overflow your container.
Stir gently after each addition of baking soda to ensure no unreacted bicarbonate remains.
After adding about a half box of baking soda, you should notice the reaction starting to slow down. At this point you may want to reduce the amount of soda you're adding each time to a teaspoon. When a teaspoon (or less) of baking soda sprinkled over the solution no longer bubbles instantly but bubbles very sluggishly as it sinks into the liquid, it's time to stop. In my experience, it's taken roughly 12 oz of baking soda to get to this point (about 3/4 of a 16 oz box).
Finally, add the retained cup of vinegar to the liquid. Since judging the stopping point can be difficult to eyeball, I've found it helpful to withhold a small amount of vinegar and add it after the baking soda reaction almost stops. This way, we err on the side of excess unreacted acetic acid (which will largely boil off) rather than excess unreacted sodium bicarbonate (which will not, and can interfere with crystallization).
Step 3 What's going on here?
Start by pouring all but one cup of the white vinegar into the boiling container (5.5 Qt or larger). (See note about acids below...)
Then, carefully add baking soda to the vinegar, small amounts at a time (no more than a tablespoon). Sprinkle it over the vinegar - don't just dump it in. If you add too much baking soda too quickly, the foam from the reaction may overflow your container.
Stir gently after each addition of baking soda to ensure no unreacted bicarbonate remains.
After adding about a half box of baking soda, you should notice the reaction starting to slow down. At this point you may want to reduce the amount of soda you're adding each time to a teaspoon. When a teaspoon (or less) of baking soda sprinkled over the solution no longer bubbles instantly but bubbles very sluggishly as it sinks into the liquid, it's time to stop. In my experience, it's taken roughly 12 oz of baking soda to get to this point (about 3/4 of a 16 oz box).
Finally, add the retained cup of vinegar to the liquid. Since judging the stopping point can be difficult to eyeball, I've found it helpful to withhold a small amount of vinegar and add it after the baking soda reaction almost stops. This way, we err on the side of excess unreacted acetic acid (which will largely boil off) rather than excess unreacted sodium bicarbonate (which will not, and can interfere with crystallization).
Step 3 What's going on here?
When you mix baking soda with vinegar, what you're really doing is reacting sodium hydrogen carbonate (more commonly, sodium bicarbonate) with acetic acid. Those components react, producing sodium acetate and carbonic acid; the carbonic acid immediately decomposes into carbon dioxide gas and water.
Step 4 Boiling down the solution
The reaction is finished, and we're left with sodium acetate dissolved in water (with a little excess acetic acid). Now, theoretically, all we have to do is boil off the excess water until we get to a metastable supersaturated state! Ideally, anyway. I've had difficulty with this part, but let's continue...
Put the solution over medium-high heat and...
Yes, watch it boil. This isn't terribly fun.
You don't want a violent boil, but you are trying to reduce the volume of the solution, so a happy medium rolling boil should be fine.
Take note of the color of the solution when you start your boil... it should be colorless (more on that later).
The observant reader will correctly infer from the pictures that I'm making a double batch.
Put the solution over medium-high heat and...
Yes, watch it boil. This isn't terribly fun.
You don't want a violent boil, but you are trying to reduce the volume of the solution, so a happy medium rolling boil should be fine.
Take note of the color of the solution when you start your boil... it should be colorless (more on that later).
The observant reader will correctly infer from the pictures that I'm making a double batch.
Step 5 Boiling, continued...
By the time you've reduced the solution to about half of its original volume, you will have noticed a color change. The solution will turn a distinct straw color, and will deepen to gold and amber the more it's reduced.
I've never found a satisfactory explanation for the color change - almost certainly it's due to organic impurities in the vinegar, owing to the natural source of the acetic acid.
My early attempts at getting the solution to a metastable supersaturated point all failed... I would get crystals if I let the solution cool overnight (with or without crystals having formed immediately on the surface of the liquid), but it seemed as though I could never get a supersaturated solution that, when cooled, would immediately crystallize when a seed crystal was introduced.
(Note about the liquid volume in the picture - recall that I'm making a double batch. There's about a gallon of liquid in that picture, which is half of what I started with.)
Step 7 Final boiling - evaporating excess water
I've never found a satisfactory explanation for the color change - almost certainly it's due to organic impurities in the vinegar, owing to the natural source of the acetic acid.
My early attempts at getting the solution to a metastable supersaturated point all failed... I would get crystals if I let the solution cool overnight (with or without crystals having formed immediately on the surface of the liquid), but it seemed as though I could never get a supersaturated solution that, when cooled, would immediately crystallize when a seed crystal was introduced.
(Note about the liquid volume in the picture - recall that I'm making a double batch. There's about a gallon of liquid in that picture, which is half of what I started with.)
Step 6 Final filtering step
Clean the strainer and the receiving container and place the strainer in position (or, if using a funnel and lab stand, prepare the funnel). This filtering step will use ten coffee filters at a time. Place ten coffee filters, nested together, into the strainer (or, folded properly, into the funnel).
Using a one cup measuring cup (or similar small container with an appropriate lip for pouring), fill the filter with hot solution and let it drain. Keep transferring hot solution into the filter until all solution has been filtered, taking care not to overfill the filter.
Clean the strainer and the receiving container and place the strainer in position (or, if using a funnel and lab stand, prepare the funnel). This filtering step will use ten coffee filters at a time. Place ten coffee filters, nested together, into the strainer (or, folded properly, into the funnel).
Using a one cup measuring cup (or similar small container with an appropriate lip for pouring), fill the filter with hot solution and let it drain. Keep transferring hot solution into the filter until all solution has been filtered, taking care not to overfill the filter.
We're almost done! We've got sodium acetate dissolved in excess water; now we just have to evaporate off excess water until we get to the right ratio of sodium acetate to water.
This part can be tricky, and it takes a fair amount of patience.
Start by bringing the solution back up to a gentle boil. Take note of how the solution "sounds" while it's boiling - specifically, how the bubbles sound. When you start to reach saturation, you'll notice that the sound of the bubbles has changed - crinkly and crackly is the best way I can describe it.
By the time you've reduced your solution by about half (see pictures), it will have turned a golden color, and you'll see a spray of fine white powder all over the inside of your pot (and, unfortunately, on your stovetop around the pot - fear not, this stuff is extremely easy to clean up).
Step 8 Final boiling - when to stop
This part can be tricky, and it takes a fair amount of patience.
Start by bringing the solution back up to a gentle boil. Take note of how the solution "sounds" while it's boiling - specifically, how the bubbles sound. When you start to reach saturation, you'll notice that the sound of the bubbles has changed - crinkly and crackly is the best way I can describe it.
By the time you've reduced your solution by about half (see pictures), it will have turned a golden color, and you'll see a spray of fine white powder all over the inside of your pot (and, unfortunately, on your stovetop around the pot - fear not, this stuff is extremely easy to clean up).
Step 8 Final boiling - when to stop
When your solution has been reduced by a little less than half (less than that if you're not sure), we'll begin removing very small samples to see if they crystallize.
Place several ice cubes or a quarter cup or so of crushed ice in a small bowl.
Using a clean cooking spoon (or small ladle), transfer a very small amount of solution (one to two teaspoons) into a clean custard dish or other small bowl; to watch for crystal formation, it's best to use a dark bowl.
Cool the custard dish containing the sample by setting it on (or holding it on) the ice (first picture). After a minute or so of cooling, blow gently on the solution to see if you can trigger crystallization. If nothing happens, you can either discard the solution or return it to the boiling solution. If you're not absolutely certain it hasn't been contaminated with dust or anything else, it's better to discard it.
Rinse the custard dish, shake excess water off (don't dry it with a towel or cloth), and take another sample after 5-10 minutes.
Eventually, you should be rewarded by seeing long, thin crystals bloom across your sample as shown in pictures 2 and 3, below (taken about 2 seconds apart).
As soon as you see this happen, remove the solution from heat and put a lid on it!
Set the crystallized sample aside and cover it with another bowl or with plastic wrap for the moment - you'll want to save these crystals to use them as "seed" crystals later, to trigger crystallization in the cool solution when you're done.
Step 9 Cooling solution
Step 10 Try it out!
Place several ice cubes or a quarter cup or so of crushed ice in a small bowl.
Using a clean cooking spoon (or small ladle), transfer a very small amount of solution (one to two teaspoons) into a clean custard dish or other small bowl; to watch for crystal formation, it's best to use a dark bowl.
Cool the custard dish containing the sample by setting it on (or holding it on) the ice (first picture). After a minute or so of cooling, blow gently on the solution to see if you can trigger crystallization. If nothing happens, you can either discard the solution or return it to the boiling solution. If you're not absolutely certain it hasn't been contaminated with dust or anything else, it's better to discard it.
Rinse the custard dish, shake excess water off (don't dry it with a towel or cloth), and take another sample after 5-10 minutes.
Eventually, you should be rewarded by seeing long, thin crystals bloom across your sample as shown in pictures 2 and 3, below (taken about 2 seconds apart).
As soon as you see this happen, remove the solution from heat and put a lid on it!
Set the crystallized sample aside and cover it with another bowl or with plastic wrap for the moment - you'll want to save these crystals to use them as "seed" crystals later, to trigger crystallization in the cool solution when you're done.
Step 9 Cooling solution
Gently pour the still-hot solution into the container you've chosen to hold the solution for cooling and crystallization. You can use a glass jar, or a flask if you have one handy. Make sure the container is absolutely clean before pouring in the solution, and loosely cover the container (with a lid, plastic wrap, or plastic baggie).
Allow the solution to cool to room temperature. You can refrigerate it or put it in an ice water bath if you wish.
There's a small chance that some of the crystals on the side of the boiling pot could have gotten washed into your container when you transferred the solution, in which case your solution may spontaneously crystallize while it's being cooled.
If this happens, recharge the solution while still in the same container (see the next step for instructions).
If you find that the solution still appears to contain crystals after double boiling for 20 minutes or so, it's possible that you've boiled off too much water. In this case, try adding two teaspoons of distilled water to your solution, stirring gently with a clean spoon after adding it, and then continue double boiling for an additional 10-15 minutes. If crystals are still visible, repeat the process - they should dissolve eventually.
Allow the solution to cool to room temperature. You can refrigerate it or put it in an ice water bath if you wish.
There's a small chance that some of the crystals on the side of the boiling pot could have gotten washed into your container when you transferred the solution, in which case your solution may spontaneously crystallize while it's being cooled.
If this happens, recharge the solution while still in the same container (see the next step for instructions).
If you find that the solution still appears to contain crystals after double boiling for 20 minutes or so, it's possible that you've boiled off too much water. In this case, try adding two teaspoons of distilled water to your solution, stirring gently with a clean spoon after adding it, and then continue double boiling for an additional 10-15 minutes. If crystals are still visible, repeat the process - they should dissolve eventually.
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Step 10 Try it out!
After your final solution has cooled to near or below room temperature (it doesn't have to be cold), it's time to see if you can trigger crystallization.
Gently set your container down on a hard surface and remove the lid or covering. Using tweezers (or clean, dry fingers), pick up one or two small crystals from the test dish you set aside in step 13, and drop them into the solution.
You should see a mesmerizing "bloom" of long, thin crystals growing outward from the crystals you dropped into the solution, growing at maybe 1 cm / sec.
Pick up the container after crystallization finishes - note how warm it is. That's excess energy, effectively stored by the supersaturated solution, and released when the sodium acetate crystallizes.
Note also that the crystals you see in the container are actually sodium acetate trihydrate. Once crystallization begins, one sodium ion and one acetate ion will join together with three water molecules. If you were to gently heat these crystals, as the water is driven off, they'd turn pure white and powdery (instead of milky white and translucent), and you'd be left with anhydrous sodium acetate.
After crystallization, recharge the solution while still in the same container by double boiling it - place the container into a pot, fill the pot with water to or just below the level of the solution in its container, and bring the water to a boil. If your container is sealed (with a lid or stopper), you'll want to break the seal first to allow for air expansion and contraction during heating and cooling.
Personal, nu am incercat dar o voi face curand... Nu pot garanta ceea ce e scris mai sus.
Pentru mai multe informatii, vizitati linkul de unde am extras cele mai importante informatii: www.instructables.com/id/Crystallization-of-homemade-sodium-acetate/
Gently set your container down on a hard surface and remove the lid or covering. Using tweezers (or clean, dry fingers), pick up one or two small crystals from the test dish you set aside in step 13, and drop them into the solution.
You should see a mesmerizing "bloom" of long, thin crystals growing outward from the crystals you dropped into the solution, growing at maybe 1 cm / sec.
Pick up the container after crystallization finishes - note how warm it is. That's excess energy, effectively stored by the supersaturated solution, and released when the sodium acetate crystallizes.
Note also that the crystals you see in the container are actually sodium acetate trihydrate. Once crystallization begins, one sodium ion and one acetate ion will join together with three water molecules. If you were to gently heat these crystals, as the water is driven off, they'd turn pure white and powdery (instead of milky white and translucent), and you'd be left with anhydrous sodium acetate.
After crystallization, recharge the solution while still in the same container by double boiling it - place the container into a pot, fill the pot with water to or just below the level of the solution in its container, and bring the water to a boil. If your container is sealed (with a lid or stopper), you'll want to break the seal first to allow for air expansion and contraction during heating and cooling.
Personal, nu am incercat dar o voi face curand... Nu pot garanta ceea ce e scris mai sus.
Pentru mai multe informatii, vizitati linkul de unde am extras cele mai importante informatii: www.instructables.com/id/Crystallization-of-homemade-sodium-acetate/
Hi,my name is Marvin.
RăspundețiȘtergereCan I post your homemade sodium acetate page(link) on my school project, a chemistry class poster?
my email is:
suzuki_bs125@yahoo.com.tw