Petroleum ether - best fractions?

[gimpy]

(PE aka naptha etc etc)

For my last few batches I've been using lab quality PE with good results (Cyb's tek, yield upto and over 2%)

So far been using a 50/50 mix of the 2 lighter fractions I have available to me which are 40-60 and 60-80

Just wondering if anyone out there would suggest tweaking either the ratio or the fractions (80-100, 100-120)? And if so, why? Would be interested to know what the absolute ideal would be

Just about to restock and been wondering this for a while so figured I'd ask here before I placed order

Cheers folks!

 

[benzyme]

depends on what you're trying to do. do you want to salt, freeze precip, or do a slow evap?
the higher boiling distillates are not pet ether, that's medium naphtha, which contains aromatics. it's best used for salting.
pet ether is the light naphtha distillates, C5-C9, and that's typically used for freeze precip or slow evap.

 

[gimpy]

Thanks benzyme. Yes I probably should have specified - this is for freeze precip

So C5-C9 best. Trying to find a nice infographic to show what range of hydrocarbons are in each fraction. It's been a long time since I was doing chemistry at school!

So would you say a 50/50 mix of 40-60 & 60-80 would be about right for getting a nice range C5-C9? Or would you suggest changing ratio more towards the lighter/heavier end of things? Or sticking purely to just one fraction of the 2?

 

[benzyme]

for freeze precip? you'd be fine with 40-60 and 60-80. the latter is basically VM&P.
when you start getting to 100-130 range, the alkaloids are more soluble, so they may not freeze precipitate out as easily

 

[syberdelic]

I have had great results freeze precipitating with VM&P.
I will usually do two iterations to get a more pure product.
It's not entirely necessary, but on the second iteration, I'll usually try to pass back and forth over the temperature where crashing is initialized to form larger and more uniform crystals. This cuts down on the oily/waxy properties and makes the stuff much easier to handle.

 

[gimpy]

Not quite sure what u mean there by iterations, syberdelic? I presume u mean something other than pulls?

Interesting technique on passing over the crashing temp there. How do you go about that exactly?

Once I've separated the NPS layer mine goes in fridge before freezer, adjusting the fridge to try find the sweet spot where it just begins to precipitate and drop the temp gradually from there. This obviously varies between pulls as the concentration differs.

 

[syberdelic]

2 iterations = freeze precipitate, pour off the Naphtha, pour in fresh warm Naphtha and let it redissolve, freeze precipitate, pour off the Naphtha, let excess Naphtha evaporate.

There is a temperature (I don't know exactly) where the DMT will begin to crash out of solution but never entirely crash out and leave material at the bottom. You want to straddle this temperature, going back and forth so that seed crystals form, new precipitate attaches to the seeds and slightly melts. Then going back below the temperature, new precipitate attaches and so on. This way, you get larger more uniform crystals and less surface area. It requires a lot of patience and time to get it right, but well worth it IMO. I always feel a lot of pride when I pull out crystals the size of a pea rather than snow flakes.

 

[Mindlusion]

I always feel a lot of pride when I pull out crystals the size of a pea rather than snow flakes.

and well placed pride that is 8)

The lighter fractions are almost always more desirable, faster evap times, low solubility.

Thankfully though, even high BP ones still evaporate fairly quickly, due to very small amount of molecular interactions holding them together.

for example, heptane boils at 98C, close to that of water.
but water has a vapour pressure of 2.3kPa at 20C, while heptane has a vapour pressure of 5.3kPa at 20C.

So it will still evaporate many times faster than water. So these solvents are great for re-crystallization.

I perfer working with fumarates myself, they don't change colour on you over time, they are very solid and never gooey, and can be easily recrystallized in boiling isopropanol to give you nice white shards.

 

[gimpy]

Alrite folks, i did a bit of an experiment with the 2 fractions

3 jars, 110g mhrb in each, cyb salt tek. fridge then freeze precip. 1st pulls measured here with 40-60, 60-80 and 50/50 mix...

Jar:
A = PE 40-60 = 494mg
B = PE 60-80 = 593mg
C = PE 50/50 mix = 668mg

Worth noting that the pulls were in series, ie B and C had a few days to soak before pulling so might of released more in that time. All 3 were done over a week but NPS added and mixed all at same time then no mixing til pulled.

Pics attached. 2 pics of each. Looks to me like the thinner fraction gives smaller more disperse xtals (although not much in it tbh) and the heavier/5050 mix pulls more plant fats hence more yellow, along with more spice. Been a while since i grew some proper fat crystals tho.

Intersting to see pure white and yellow xtals next to each other in the same dish on the 60-80 pull

So there we go. As the results suggest, it looks like we have a winner. 50/50 from here on in... wud be good to reproduce this experiment... just depends how geeky you wanna get!

 

[steppa]

depends on what you're trying to do. do you want to salt, freeze precip, or do a slow evap?

What's the best for fast evap? Is the a way to evap fast without yieling mostly goo?