what is the phenomena called "overgassing"
"Overgassing" is the phenomenon of red/brown/amber oil/wax forming in a non-polar solution when introducing more than one equivalent of HCl gas into a solution of an amine freebase. It is caused by impurities polymerizing (acid-catalyzed condensation) and oiling out of these compounds (due to the solvent becoming more polar from dissolved HCl) due to lessened solubility.
With really pure, fractionally distilled freebase in a pure, inert solvent the "overgassing" phenomenon seldom appear, unless enough acid is introduced to decompose the amine.
I don't see why a nonpolar solvent with a small percentage of H2O shouldn't be able to carry enough ions to allow for proper pH measurements?
Solubility of water in toluene, 0.033% at 25°C. Ref: http://macro.lsu.edu/howto/solvents/toluene.htm (http://macro.lsu.edu/howto/solvents/toluene.htm)
As far as I know, it hasn't got to do with the solubility of ions in the solvent, but rather that the definition of pH requires the measurement to be made in an aqueous solution. If you insert a wet pH electrode in a non-polar solution, you aren't measuring the pH of the non-polar solution, but rather the pH of the aqueous film on the electrode surface (and that isn't the same thing).
I always thought that for crystal formation, the molecules would need a possibility to move to their destined place in the crystal matrix, and this needs some solubility and some time (we all know this). But if the solvent is absolutely anhydrous (i.e. absolutely non-polar), these two requirements are not met, and the result will be an amorphous mass, rather than crystalline
For all practical purposes, you need to recrystallize the precipitate anyway to get proper crystals. Also, there are several steps inbetween "amorphous masses" and "crystalline solids", and a few reasons why follows here:
Reality vs. Ideal theoretical approximation
Anhydrous toluene isn't absolutely non-polar. Toluene is a non-polar solvent.
Amine salts doesn't have zero solubility in toluene. Salts aren't soluble in toluene.
100-10000 µs pass before formed salts crash out. Salts precipitate immediately when amines are gassed with HCl.
You can doubt whatever you want - still overgassing can happen, and gassing to pH 5 (measured however you like) is the way around this.
About pH of solutions you should check http://www.google.com/search?hl=en&lr=&ie=UTF-8&oi=defmore&q=define%3Aph (http://www.google.com/search?hl=en&lr=&ie=UTF-8&oi=defmore&q=define%3Aph)
One definition of "pH" I found there, being rather concise:
"A logarithmic scale for expressing the acidity of a solution. pH is an abbreviation of "potential of hydrogen" and is in effect a measure of the amount of hydrogen ions, expressed on moles per cubic decimeter (10m x 10m x 10m, or 1000m3) The pH scale goes from 0 - 14. A value of 7 is neutral (i.e. neither acid or alkaline). Values below 7 indicate an acid solution, whilst values greater than 7 indicate an alkaline solution. For every increase in pH of 1.0, the alkalinity increases ten fold (and for every decrease of 1.0, the acidity increases ten fold. Therefore a solution at pH8.5 has ten times less acidity of a solution at pH7.5. Rapid changes in the pH of the water can stress fish (and also other organisms such as bacteria in biological filters). "
And another one, being more scientifically correct:
"(chemistry) p(otential of) H(ydrogen); the logarithm of the reciprocal of hydrogen-ion concentration in gram atoms per liter; provides a measure on a scale from 0 to 14 of the acidity or alkalinity of a solution (where 7 is neutral and greater than 7 is acidic and less than 7 is basic)."
And this one is from our beeloved US government:
"Represents the negative base-10 logarithm of hydrogen ion activity of a solution in moles per liter; a measure of the acidity (pH less than 7) or alkalinity (pH greater than 7) of a solution."
Please note the word "solution" is used in all definitions - not "water"!
Another one, also from a government institution:
"A measure to indicate an acid or alkaline condition; pH values can range from zero (extremely acidic) to 14 (extremely basic or alkaline). pH measurements are based on a log scale such that pH 6 is 10 times more acidic than pH 7 (neutral) and pH 5 is 100 times more acidic than pH 7."
(all those definitions can be found via the page I linked to)
(and if I had suggested the buy of a pH/mV-meter, I would not have mentioned that strips can be used too)
indole_amine
There are so-called "narrow range pH strips" out there - they give you a value within 1/10th pH exactness...
These will not give a reliable figure either, when wetted and put into a non-polar solution, only in water. The best value you can ever get is what's said in Post 533616 (https://www.thevespiary.org/talk/index.php?topic=10294.msg53361600#msg53361600)
(hypo: "of course not!", Newbee Forum)
Electronic pH meters are calibrated for use in aqueous solutions, and will give erroneous values in other solvent mixtures.
Show me a link to somewhere where it is said that glass probes with Ag electrodes and potassium electrolyte aren't able of measuring in other media than water, and I will believe you.
"Glass membrane pH probes rapidly dehydrate and lose response in non-aqueous solutions"
Source: http://multitrator.com/downloads/Multitrator_Thermometric_Titration_Introduction.ppt (http://multitrator.com/downloads/Multitrator_Thermometric_Titration_Introduction.ppt)
"...precludes titration in non-conducting environments, for instance, many non-aqueous solvents.
Probes such as pH electrodes perform very poorly under such circumstances."
Source: http://multitrator.com/FAQs.htm (http://multitrator.com/FAQs.htm)