Crystallization of homemade sodium acetate

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.

The next few steps attempt to remove as much of the impurities as possible, and it is up to you whether you want to follow them or continue boiling. (If you decide to skip them, go to step 11.)

(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.)

Comments

[amira1295]

when I added the baking soda and started to boil as instructed my substance didn't turn a different color. it stayed clear. did I do something wrong?

[mikey2110]

the color change is a result of the electrons bonding. when the vinegar and baking soda react they start to share electrons. there is this thing call the vanadium goddess where you have Zinc and vanadium and you shake and it changes colors like seven times.

[indigoandblack]

Erm, no. The color doesn't have anything to do with the sodium or the acetate. (Besides which, after the reaction completes, the result isn't a bonded sodium acetate molecule, but rather sodium and acetate ions in solution). If one were to use pure acetic acid instead of white vinegar, the color won't appear. Now the other thing you describe... I've never heard of it, and offhand can't find any references to such a solution (presumably it's a solution) called that... but it sounds like a reversible reaction that takes energy from the mechanical shaking. Sounds interesting... do you have any more information about it? (Are you sure you're not getting the "goddess" part from the element Vanadium, which was named after the Norse goddess Vanadis (Freyja)?) I have a recipe for a similar solution. It doesn't have a name, but it uses sodium hydroxide, dextrose, and indigo carmine dye, and if I recall correctly, it produces three colors - one at rest, one after being shaken gently, and one after being vigorously shaken. Hm... If I can find the recipe, perhaps I'll have to post another Instructable... :-)

[indigoandblack]

Ah, found it! Actually, it appears to be a fairly common one, and the color change has to do with dissolved oxygen in the solution. Search for "sodium hydroxide dextrose indigo carmine" and you'll find it. My recipe calls for 400 mL water, 10 g NaOH, 6 g dextrose, and a pinch of indigo carmine dye (a pH indicator). I've seen at least two recipes online that call for exactly half that, so I think the proportions are good. (NEEDLESS to say, should you, reader, choose to go make this stuff, the outcome is YOUR responsibility - sodium hydroxide and indigo carmine dye aren't safe things to play with.)

[Ed H]

Perhaps if you filter out some of the organic material from the solution before the liquid changes color, the resulting color won't be as dark. This is going off of the idea that the color change comes from boiling the organic substances. I guess you'd have to filter way more liquid, though, and that would take a long time.