Titrations

[highRvibratoryfreq]

can some of the helpful nexians please shed some light on the best methods for performing a successful titration using a 250ml seperatory funnel, regular funnels and cotton filters and a digital ph meter.

ive been running into some horrible emulsions salting out of xylene with sulphuric acid solution, ive been keeping the solutions ph at 3 and shaking it re-testing and adding more ph3 solution to bring the ph down to 6-7. i struggle getting conistent readings with my ph meter. it was cheap which could be a problem. also i find if i seperate the salting water around ph 8-9 then add fresh ph3 solution it levels off at 6-7 without me have to keep repeat shaking which is the cause of the bad emulsions, which take a long time to clear with funnels and cotton.

is it more effective to roll for a few minutes rather than shake, i know this will help with emulsions but will it grab all the alks effectively this way?

i guess ill get the hang of it with practise but it would be nice to have some pointers to get me there a bit quicker as i find this quite time consuming to say the least

thanks

 

[InMotion]

I'm a bit confused here as to what you're doing. I see no real reference here to a titration so the title is misleading.

Are you measuring the pH of xylene with your pH meter? If so, well good luck with that hehehe. pH meters weren't made to do that.

Salting out of xylene at pH 3 should work fine. Then you mention adding more pH 3 solution to bring the pH down to 6-7? Bringing down the pH of what?

 

[highRvibratoryfreq]

sorry for the sloppy explanation..

im measuring the ph of the ph3 solution that was added and shaken with the nps, it goes up accordingly as it salts out the alks i keep adding more till it comes down to 6-7 but it never seems to come down, my guess is that reading the ph of the slightly emulsified solution just isnt possible with my ph meter(as the nps thats emulsified is throwing off the reading) and when i remove and filter the first salt then add more ph3 water i start to get a clearer reading.. and i manage to get it down to
6-7

i guess my main question was: is it better to gently roll nps and the acid solution rather than shaking? im currently testing this but thought id ask for advice aswell..

 

[dg]

i shake violently...
then let solution sit in near boiling water
"Most" of the emulsions will break- some filtering is still needed though

 

[highRvibratoryfreq]

i was shaking violently, but the emulsions i had just werent breaking even after heating in near boiling water for an hour.. was coming out the texture of a well mixed salad dressing!

which took another couple of hours to break up through the filters.

do you agree that my digital ph pen could be giving innnacurate readings due to the emulsions throwing it off?

when i was shaking the ph just didnt come down i'd recheck atleast 10 or 20 times and i kept adding more acid water (too much i think) , i tried just rolling instead of shaking a pull last night and i ended up using a lot less acid solution to get it to 6-7

 

[Infundibulum]

do you agree that my digital ph pen could be giving innnacurate readings due to the emulsions throwing it off?

Could be; how did you calibrate your pH meter? All instruments of measurement need calibration (even the common ruler needs calibration). Also, even presence of solvents like xylene can interfere with pH measurements.

...and adding more ph3 solution to bring the ph down to 6-7.

when i was shaking the ph just didnt come down i'd recheck atleast 10 or 20 times and i kept adding more acid water (too much i think) , i tried just rolling instead of shaking a pull last night and i ended up using a lot less acid solution to get it to 6-7

You might need to use better terminology here; if you have a solution of pH=3, bringing it down means bringing it towards 2, 1, 0, -1 etc. Bringing it up means 4, 5, 6, 7, etc. When you salt alkaloids with acidic water you'd expect the pH to go slightly up due to the acid being neutralised by the alkaloids.

also i find if i seperate the salting water around ph 8-9 then add fresh ph3 solution it levels off at 6-7 without me have to keep repeat shaking which is the cause of the bad emulsions, which take a long time to clear with funnels and cotton.

This sentence really makes no sense !

I think that you just need to stop thinking too much about pH measurements, just salt things out and evaporate them; when you salt things out and nothing comes upon evaporation, then that's you, you salted everything.

 

[highRvibratoryfreq]

I calibrated with the ph calibration solution provided with the meter.

again my explanation is very sloppy ill try again

I add the ph3 sulphuric acid solution into the container with the nps and about 30mls of plain distilled water, shake then pipette out enough of the acid water to get a reading. it goes up say to around 9-10
now i keep adding more ph3 solution and re shaking to bring it down to the 6-7 mark but it just doesnt want to get down unless i remove it completely filter it set it aside and then start with fresh ph3 solution added back into the nps shake pipette and read

I hope that makes things a bit clearer.

I am getting all the alks out in the end i know that for sure.. i just want to find the quickest most efficient method of doing so without oversalting and contaminating my final product....

 

[Infundibulum]

A pH of 9-10 after salting does indeed sound spurious, especially since at this pH mescaline is more likely to be a freebase. I would normally suspect a poor pH measurement, but then again not many people measure and report pH changes after salting.

adding more pH 3 water and bringing the pH down to 6-7 sounds correct - you might not be able to alter the pH dramatically at this stage (as you observe), probably due to the complex composition of your solution now (that is, sulfuric acid and mescaline sulfate), which means you have a buffer solution. Of course, draining this solution off and adding fresh pH 3 water restores the low pH as you observe.

Now, there is truly no need to go so anal about extractions, just salt and evaporate till no yield.

.. i just want to find the quickest most efficient method of doing so without oversalting and contaminating my final product....

There is of course no danger of oversalting - your only salt can be mescaline sulfate (and sulfates of other cactus-containg alkaloids). There is the danger of residual sulfuric acid (which in your case of salting with pH 3 water will be absolutely minuscule) , which can be removed by washing the mescaline sulfate with acetone or isopropanol.

 

[highRvibratoryfreq]

so any excess sulphuric acid would be negligble and it would not make it into the final product if it was being dual solvent re-x'd out of acetone?

the final product does seem pure still slightly waxy.. i was just worried i was getting excess sulphuric acid contamination...

so dropping the ph below 6-7 isnt bad ill just pull more crap (other cactus alks) out of the nps, now will this extra crap affect the dual solvent re-x?

im guessing i dont have to be nearly so precise with these measurements if im recrystallizing the final product..