matto70799 - 25-6-2015 at 18:36
hi.
Question for the masses: I generated a solution of calcium acetate by reacting calcium carbonate with an excess of acetic acid. I started to
neutralize the solution with sodium hydroxide however every drop of hydroxide is generating a precipitate as I add it. Anyone know what is
precipitating out and how I can neutralize the solution so I can use it to give my hydroponic garden some much needed soluble calcium?
Thanks.
Matto70799
Loptr - 25-6-2015 at 18:59
Why are you using sodium hydroxide? Just keep adding calcium carbonate to neutralize all the acetic acid.
violet sin - 25-6-2015 at 19:36
calcium acetate works great for gardens. saved a bunch of my garden( containers- concrete back yard) from blossom rot and fruit loss that way.
tomatoes, squash, melons mainly. one tomato even had a soft spot mushing in after getting 3/4 ripe. the soluble nutrient actually firmed it up and
continued to finish. not the best looking 'mater, but great on a sandwich.
I don't know why no one sells it in the garden stores... they looked at me like I was retarded when I told them that. kept talking about the crabshell
stuff they had, was fast(er) release than oyster shell... but the price, not great, and it wouldn't have worked for hydro.
slacked lime + vinegar. add lime until there is some left in the bottom after a day. filer it to a light straw colored clearish liquid. I set mine
out side in several quart mason jars, under a black 5gal bucket set upside down on them. it gets hot here 105'F that week, dried to a powder in 2
days or so. you can use it right after filtering as a liquid, but I wanted to store it and be able to measure out specific proportions on the go. if
left in a jug for too long, it will rot/mold on the surface.
oh ya, if you overshoot your pH too high with left over slacked lime in the bottom of the jug the way I did it - don't use the phosphoric acid pH up.
it will drop you calcium out as it adjusts pH down. just use more vinegar.
I used slacked lime and vinegar because of ease, but I see you are using the carbonate and acetic. is that burnt oyster shell or a straight calcium
carbonate? regardless, you could use slacked lime or more calcium carbonate for pH up, and acetic for pH down.
[Edited on 26-6-2015 by violet sin]
[Edited on 26-6-2015 by violet sin]
matto70799 - 28-6-2015 at 19:32
Hi.
Thanks for your replies. I used hydroxide because it's what I have on hand.
What I decided to do was to dry my solution and collect the calcium acetate. I can then make solutions of known calcium content instead of estimating
it based in theoretical yield.
Pumukli - 28-6-2015 at 22:29
What does the formed precipitate do after you swirl the flask? Does it disappear or just stays there?
I suspect that the precipitate is Ca(OH)2 and is forming due to the local high pH around the NaOH droplet and the bad solubility of
Ca(OH)2 in general. If you are still on the acidic side then after swirling the flask it should disappear. If it doesn't, then you should
check the pH first because you might already be on the basic side!
As a sidenote: if you intend to use this Ca-acetate on plants then it is safer to be err on the acidic side because plants tolerate considerably more
deviation from neutral into the acidic region (down to pH 4-5) without any harm than into the other side! pH 9 can cause more trouble than pH 5!
Bio-growers use acetic acid as a weedkiller, the concentration in this case is around 10%! It is still tolerated by some plants (garlic e.g.) while
not by the seedlings of most weeds.
[Edited on 29-6-2015 by Pumukli]
violet sin - 28-6-2015 at 22:54
how did you dry it? if heated what temp? I did mine with the higher than usual ambient temp outside over two days because heating it too much, like
an oven( >320'F), will decompose your product to acetone and calcium carbonate = back to square one. partial decomp would mean insoluble portions
of the solution, possibly clogged plumbing on your hydroponics setup and depending on the degree of degradation, inaccurate nutrient in the water
system.
I still had some insoluble bits when the dried product was mixed up for a batch of fertilizer. left over slacked lime too small for the filter? tap
hardwater for mixing? either way it wasn't much.