sarumpaet - 6-4-2021 at 09:34
I want to convert a solution of nicotine freebase to nicotine benzoate, using sodium benzoate as a starting material. I'm using the sodium salt
because I already have it - benzoic acid is cheap and readily available, but my main purpose here is to check my understanding of the basic chemistry,
not the economic manufacture of nicotine benzoate. I think it should be pretty simple, but this seemed like a prudent point in my self-education to
check in with some other people, before mixing up a concoction that I intend to vaporise and inhale.
Basically, the idea is to precipitate benzoic acid from a solution of sodium benzoate using hydrochloric acid, and add a stoichiometric quantity of it
to the nicotine freebase solution to obtain a solution of nicotine benzoate. My main concern is that I'm going to mess up the numbers, but I would
also really appreciate some sort of feedback about whether my intuitions are correct. I've tried to explain my reasoning in the hope that someone
might let me know if I'm making any mistakes.
I was thinking it might work something like this:
1. Stir 50g sodium benzoate into 100mL of distilled water. The salt should fully dissolve and partially dissociate at room temperature, resulting in a
3.47 M solution of sodium benzoate.
2. Add 34.7mL of 10 M hydrochloric acid. I think this is pretty close to what my hardware-store 31.5% hydrochloric acid is. The stronger acid
protonates the weaker one, or looking at it another way, benzoate anions and hydronium ions (present in the water) are the right-hand side of the
dissociation equilibrium reaction for a carboxylic acid, which is driven in reverse under acidic conditions. Benzoic acid precipitates, leaving sodium
chloride in solution. A small excess of HCl may be used, but excess water will cut into the yield, since benzoic acid is slightly soluble (3.4g/L @
25C). If using acid of uncertain concentration and purity, it would be a better idea to mix in half the expected volume of acid and titrate up until
no more precipitate appears.
Here I assume that benzoic acid will not be attacked by HCl, owing to the stability of the benzene ring, but it's a guess - please let me know if this
is not the case!
3. Filter off the precipitate in a Büchner funnel, the filtrate can be neutralised if necessary and poured down the drain. Dry and weigh the
collected solid, which should be fine white crystals. The stoichiometric yield of benzoic acid is around 42.38g, expect no more than 42g at room
temperature.
4. Combine the collected benzoic acid with the nicotine freebase solution in equimolar ratio, with gentle heat and stirring until all of the solid
dissolves. Again, if there is any uncertainty, it would be better to add less, and work up until no more benzoic acid will dissolve - then chill the
solution and filter off any benzoic acid that precipitates. This is a simple neutralisation of a weak acid with a weak base, yielding a salt solution
of nicotine benzoate.
Does this sound reasonable?
[Edited on 6-4-2021 by sarumpaet]
njl - 6-4-2021 at 10:05
Benzoate/benzoic acid will be stable to these conditions. Unless there is a problem with benzoic acid being soluble at low pH, I would skip step 1 or
cut down on the amount of water. You could either form a more concentrated solution of benzoate by heating Na benzoate with minimal water (microwave
works well for this), of just add the Na benzoate directly to the HCl. This is not exactly best practice but as you noted benzoic acid is somewhat
soluble so cutting down on water throughout the process should be beneficial.
When neutralizing the nicotine freebase, it may be better to work with a solvent system that precipitates nicotine benzoate while holding the freebase
and acid in solution (if such a system exists). This will prevent the coprecipitation of excess benzoic acid. If the purpose of this experiment is to
go from benzoate -> benzoic acid -> nicotin(ium?) benzoate then looks good. If you're after the nicotine benzoate itself then I think combining
solutions of nicotine HCl and Na benzoate in ethanol might be better.
sarumpaet - 6-4-2021 at 17:58
Thanks njl, I appreciate the feedback and suggestions. It is indeed the aqueous solution that I am after, but I do appreciate the advice on how to
recover the dry salt.
My concern with using less water is that 50g into 100mL is already pretty close to the solubility limit (66g/100mL), but I totally missed (despite
skirting so close to seeing it) that adding another 35mL of HCl solution would actually bring the water excess to just over 2:1, taking the expected
losses above 1%, which I'd prefer to stay under. Especially since, as you say, following your advice could reduce that expected loss almost to
insignificance.
Yet I'm still not convinced this (nor adding the NaBenzoate to HCl) a good idea for me, using tech grade HCl. As of 2019, the SDS of this product no
longer lists titanium dioxide as a hazardous contaminant, but I still don't trust to it to be pure of non-hazardous contaminants that may nevertheless
have unforeseen interactions, I also don't especially trust the stated concentration to be accurate to within a few %.
This seems to leave me with a problem: the stoichiometric approach inherits that uncertainty. How do I know that all of the reagents have been
consumed? Fully dissolving the sodium salt in water first gives me a useful indicator - two colourless liquids precipitating a white solid, until they
don't. Otherwise I have a white powder being converted into a white powder, with no easy way to recognise the contingency where the store-bought HCl
is a good few % less concentrated than it was sold as, leaving sodium benzoate mixed in with the benzoic acid precipitate. The alternative of using
excess HCl defeats the purpose of using less water.
njl - 6-4-2021 at 18:39
If this is for consumption you should absolutely err on the side of caution, in this case some leftover Na Benzoate (which is harmless, although I
don't know anything about its compatibility with vape products). That said, I personally wouldn't have any problem with using that HCl. Typical
contaminants are iron, sulfur, and a few other trace compounds. The precipitated acid will contain a small amount of the already trace contaminants
and a wash with cold water should give a clean enough product. Point being, if I was doing this I would add a slight excess of ice cold HCl diluted to
~75 mL, slightly more if NaCl solubility is a problem. That way the total volume is minimized throughout. Given the very low pH and temperature I'd
expect a good recovery of benzoic acid. However, that doesn't really seem like your style so perhaps take it as an alternative route that may be a bit
cleaner and easier.
sarumpaet - 6-4-2021 at 19:05
Haha, thank you for being tactful, but my style is not something that is important to me in a field I am just beginning in, this forum has already
been a tremendous influence on me (long time reader) and I take your suggestions very seriously. I need to learn to think like a chemist and I don't
want to waste time hanging onto anything that might be considered "my way". I don't have a way yet, you are helping me find one!
Thank you for the tips. They make sense to me. I probably won't update the original post, but I will change the procedure I actually perform and the
version of it that I record in my logbook. And I will do so with some confidence, thanks to your advice.
draculic acid69 - 10-4-2021 at 05:01
Just keep in mind that anything you make may still be contaminated with hcl which U definitely don't want to be vaporizing.thoroghly remove all hcl
traces before vaping
Metacelsus - 10-4-2021 at 07:58
I'd be worried about vaping benzoate salts. They might decarboxylate when heated and produce benzene. Benzene production from sodium benzoate has been
reported on this discussion board. http://www.sciencemadness.org/talk/viewthread.php?tid=31648
Otherwise this method seems OK to me.
[Edited on 2021-4-10 by Metacelsus]
earpain - 10-5-2021 at 23:06
I, one time neutralized my freebase nicotine, dissolved in propylene glycol, at 100mg/ml, with HCl, in an attempt to form nicotine hydrochloride.
I'm assuming you have nicotine in that same form, since it's kind of a miracle that one is even able to buy nicotine in ANY form OTC, but I know that
the REAL stuff, 1000mg/ml is commercially available but I do believe would kill you on skin contact..
I think your main issue will be the same issue one encounters when making vape juice mixes. To a greater extreme glycerin, and still to a moderate
extreme propylene glycol, are viscous, slow moving, syrups. Hence, once needs to either steep for a month, or stir for one hour via proper magnetic
stirrer, while heated, to conclude the preparation of any e-juice.
So the issue, specifically, is that you probably won't be able to easily measure Ph.
We already know that nicotine freebase, when dissolved in propylene glycol, and then diluted significantly is safe to vape. We also know this for
several acids, such as citric acid and the other various 'tart' flavorings. I'd suggest having a variety of methods for measuring Ph handy in case
one proves useless, you can use others and see if there's an average etc.
I'd recommend purchasing benzoic acid rather than making it yourself, via your proposed method, if you wanted to take additional safety measures
@ Metacelsus
That guy that owns the entire media successfully patented nicotine benzoate and created his company 'Jul'. nicotine benzoate is known to the consumer
as "nic salts". The basis of his patent was that it turns out one can easily injest much much larger quantities of nicotine, via aerosol in propylene
glycol/glycerin, without unpleasant harshness. Before this discovery, very beefy vape devices were needed to mimic the nicotine levels that, for
example, a former tobacco smoker was used to.
So with nic salts, one can just use a tiny little pen, take tiny little puffs, and it's quite satisfying. I'm still dinosaur age and am too in love
with my devices/juice mixes that are made via the older paradigm =D
[Edited on 11-5-2021 by earpain]