- #1
cotarded
- 45
- 0
Problematic "Synthesis" of Sodium Acetate
Greetings all, was hoping someone more knowledgeable than me (not a tall order, by any means) could point out some errors in my theory or method here.
Fascinated by pictures of supersaturated NaCH3OOH solutions crystallizing at the drop of a dime (or a seed crystal, at least) and thinking a synthesis should be easy (vinegar and baking soda, right?) I decided to give it a try.
I started with 250mL of White Distilled Vinegar, which I used in lieu of diluted acetic acid (which I don't have). The labeling claimed the contents had been adjusted to 5% acidity, which, after a little web searching, I understood to be 5% acetic acid by volume (could this be the error?).
So my calculations were:
.05 * 250 = 12.5mL of acetic acid.
12.5mL = 12.5cm^3;
12.5cm^3 / 1.049g/cm^3 density of CH3OOH = .198436... mol (of course taking that many decimal places is absurd with the inaccuracy of my measurements but w/e.)
.198436 mol * 84g/mol (molar mass of baking soda) = about 16 2/3g NaHCO3.
So I weighed 16 grams of sodium bicarb on my fairly inaccurate gram scale and stirred it bit by bit into my 250mL distilled vinegar.
A few more calculations were made here.
Using the density of Sodium Acetate (which I supposed I probably had a good bit of, though probably contaminated with excess sodium bicarb/acetate/unlisted anti-caking agent from baking soda/impurities in vinegar) I figured about 21mL of water would be the saturation point.
I boiled the liquid down, using the microwave as I wanted to avoid boiling any possible residual acid in a metal container on the stove, to a little below this point (can't tell precisely; was below the accuracy of the container) and it abruptly turned into a bunch (about 16g) of chunky white powder.
I had been hoping for something far more crystalline, but still had hope because within the chunks, shimmering bits of salt-like crystal were visible.
Seeing the decomposition point for sodium acetate (and baking soda, etc, for that matter) was pretty high, I decided to heat this, since it might be sodium acetate tryhydrate, which can be returned to a liquid state at 54C. At this point the texture changed utterly and it seemed two disparate substances were present: a still mostly white, VERY chunky material, and a browned, extremely fine grain powder.
The white chunks are definitely not sodium bicarb, and they are not very soluble. The brown powder leaves a glassy coating if I dissolve it in water let dry, but I have so little of this left after doing a few careless tests that I am not able to test if it is mostly sodium acetate.
Any thoughts? Should I retry the whole bit reading the 5% acidity labelling as acetic acid by weight? (with my inaccurate equipment and the parity of h2o's and ch3ooh's densities this may not even make much of a difference.) Are the unexpected characteristics of my result due to impurities in the vinegar?
lates,
cotarded.
Greetings all, was hoping someone more knowledgeable than me (not a tall order, by any means) could point out some errors in my theory or method here.
Fascinated by pictures of supersaturated NaCH3OOH solutions crystallizing at the drop of a dime (or a seed crystal, at least) and thinking a synthesis should be easy (vinegar and baking soda, right?) I decided to give it a try.
I started with 250mL of White Distilled Vinegar, which I used in lieu of diluted acetic acid (which I don't have). The labeling claimed the contents had been adjusted to 5% acidity, which, after a little web searching, I understood to be 5% acetic acid by volume (could this be the error?).
So my calculations were:
.05 * 250 = 12.5mL of acetic acid.
12.5mL = 12.5cm^3;
12.5cm^3 / 1.049g/cm^3 density of CH3OOH = .198436... mol (of course taking that many decimal places is absurd with the inaccuracy of my measurements but w/e.)
.198436 mol * 84g/mol (molar mass of baking soda) = about 16 2/3g NaHCO3.
So I weighed 16 grams of sodium bicarb on my fairly inaccurate gram scale and stirred it bit by bit into my 250mL distilled vinegar.
A few more calculations were made here.
Using the density of Sodium Acetate (which I supposed I probably had a good bit of, though probably contaminated with excess sodium bicarb/acetate/unlisted anti-caking agent from baking soda/impurities in vinegar) I figured about 21mL of water would be the saturation point.
I boiled the liquid down, using the microwave as I wanted to avoid boiling any possible residual acid in a metal container on the stove, to a little below this point (can't tell precisely; was below the accuracy of the container) and it abruptly turned into a bunch (about 16g) of chunky white powder.
I had been hoping for something far more crystalline, but still had hope because within the chunks, shimmering bits of salt-like crystal were visible.
Seeing the decomposition point for sodium acetate (and baking soda, etc, for that matter) was pretty high, I decided to heat this, since it might be sodium acetate tryhydrate, which can be returned to a liquid state at 54C. At this point the texture changed utterly and it seemed two disparate substances were present: a still mostly white, VERY chunky material, and a browned, extremely fine grain powder.
The white chunks are definitely not sodium bicarb, and they are not very soluble. The brown powder leaves a glassy coating if I dissolve it in water let dry, but I have so little of this left after doing a few careless tests that I am not able to test if it is mostly sodium acetate.
Any thoughts? Should I retry the whole bit reading the 5% acidity labelling as acetic acid by weight? (with my inaccurate equipment and the parity of h2o's and ch3ooh's densities this may not even make much of a difference.) Are the unexpected characteristics of my result due to impurities in the vinegar?
lates,
cotarded.