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pH of naptha (non polar solvent, NPS), precipitate without aqueous soln

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saphdmt

Rising Star
After a bit of experimenting I was left with two batches of naptha; one that was leftover from a backsalting, which is very slightly cloudy and light yellow translucent, and another batch that was left over from a freeze precipitation, which is a little yellower than the other. The backsalt one smells of acetic acid, and I decided to check its pH. To my surprise it was acidic, around 3.4. The other was slightly basic around 8.0. There were no aqueous layers in either.

When added dropwise to one another a precipitate forms.

Can someone explain the chemistry here? Im not so clear on how pH works when were talking about things other than H2O. I dont think NaOH is soluble in naptha, nor NaCl. This only leaves the acetate anions, or the active ingredient.

Im guessing the precipitate is a salt but its precipitating from naptha, not water. Could it be sodium acetate? I dont know which batch contained the mystery precipitate, so I dont know if it was resulting from a raise or lowering of pH.

Questions:

1) Is NaOAc soluble in naptha?

2) How does pH work when dealing with NPS?

3) What is the precipitate?

Thanks very much, you guys are the best!
 
Is it possible there are tiny suspended droplets of the acqueous acidic or basic solution in your solvents? Im not a chemist but from what i understood, pH can only really be talked about in the presence of water.

So if there are tiny drops of the acqueous solutions in your solvent,that would explain the pH reading, and in that case the precipitate would be indeed sodium acetate. If you would wash your solvents with water before mixing them, then no precipitate should form if thats the case
 
A lot of sensors give an output when they get washed over with stimuli of different kind than their supposed target molecules. False positives are well known.
I've found pH paper also sensible to deviating from pH probe in some cases (up to 1 pH easily), while in other cases matching perfectly. The answer is in the soup?

Sensors out of their meant media going squarely bananas, no wonder to that.
Good question saphdmt nonetheless, an on the fringe one ;)
 
There are maybe 5 or 6 tiny aqueous spheres floating on the bottom of the 600ml beaker, which is about in inch full with solvent; the spheres are less than a millimeter diameter each; they were probably originally part of an emulsion that made its way through the stopcock. Given their size and location I would say there is no way they would have an effect on the pH probe, or even come in contact with it.

There is also a barely discernible precipitate (or so it appears) floating in the solvent... This was noticed after picking it up after 12+ hours of immobilization.


Regarding your suggestion of washing- what is a good pH to wash freebase containing solvent with? When backsalting is unwanted I mean... I would imagine that anything under 10.5 would start noticeably diminishing yields (per the freebase percentage calculator, a pH of 10.7 is required to keep 99% in freebase form)

According to same, a pH of 7 results in 97% of the active in salt form. Why is this not mentioned prominently whenever someone suggests to wash their solvent to remove impurities? Wouldn't someone grabbing a gallon of distilled water (around neutral pH) inadvertently destroy their yield if the water ends up down the drain?
 
saphdmt said:
...Regarding your suggestion of washing- what is a good pH to wash freebase containing solvent with? When backsalting is unwanted I mean... I would imagine that anything under 10.5 would start noticeably diminishing yields (per the freebase percentage calculator, a pH of 10.7 is required to keep 99% in freebase form)

According to same, a pH of 7 results in 97% of the active in salt form. Why is this not mentioned prominently whenever someone suggests to wash their solvent to remove impurities? Wouldn't someone grabbing a gallon of distilled water (around neutral pH) inadvertently destroy their yield if the water ends up down the drain?
This is a lively item, have some read here please:
Does washing solvent layer with water reduce yield?
 
1. Sodium acetate is insoluble in naphtha.

2. Sticking a pH probe in a non-aquaous solvent makes no sense, as pH is only defined in terms of the proton dissociation in water. Sticking a pH probe in a non-polar aprotic solvent is even more useless.

The readings that you got are actually readings of the water-wetted surface of the probe. Tiny droplets, microemulsions and possibly even dissolved undissociated acetic acid (it is a weak acid) in the non-polar solvent will preferably move to the aquaous layer on the surface of your probe. The changes on the surface of the probe are not an accurate representation of the situation in the non-polar solvent, at best they can be seen as a very rough indication.

3. The precipitate that you got by mixing vinegar washed naphtha and freeze precipitated naphtha might well be dmt acetate salt. It's just a guess, but since the washed naphtha contains some traces of acetic acid, either dissolved or as microemulsion, and the frozen naphtha contains some dmt freebase (not all dmt will precipitate out when freezing) it is certainly possible.

I don't think that microemulsions of NaOH solution would survive freeze precipitation and it certainly is not soluble int naphtha, so it seems unlikely that the precipitate is Sodium acetate. I can't rule that, or other hypotheses, out though.
 
chemspider.com


You should try doing this extraction completely naked, using bhut jolokia peppers as the source of capsaicinoids. [YOUTUBE]

Also, did you know about this thing called The Study of Chemistry? The book I am adding a link to should do a decent job at educating you on this subject better than us dumb-arseschwitzes can. https://drive.google.com/file/d/0B-U5UnOdEpmLcnB6MXVyZmZNX2M/view?usp=sharing
 
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