Why start with hot water for CWE of codeine

[HabitualCriminal]

Ok, swim has been thinking about the method of CWE and has a question which may seem stupid but swim has searched all over looking for some sort of answer and cannot find one. Anyway, all the CWE guides swim has found say to start with warm water, mix in the crushed pills, stir and cool to say 4 degrees and then filter. Swims question is, why start with the hot water, if the APAP is less soluble in cold water and the Codeine is more soluble, why not just mix the crushed pills in ice cold water and filter straight away? Has anyone ever tried this?

Swim realises there must be a reason for it but would just like it explained. Thanks.

[Pondlife]

Because it's quicker, that's why.

If you are doing a CWE to separate a substance that is reasonably soluble in cold water (Codeine in your example) from some other stuff that is less soluble, then you want to use the minimum volume of water that the amount of Codeine will dissolve in because that will minimise the amount of the less soluble stuff that will remain in solution and end up in the final product.

The problem with doing it cold is that the rate that a substance dissolves slows down as the solution becomes stronger, and approaches zero as the solution becomes saturated. So if you try to dissolve something in exactly the right amount of cold water it will take ages to get it all to dissolve.

By contrast, if you dissolve it in hot water it will dissolve quicker because there is an excess of water at that temperature. You can then cool the solution down and the less soluble stuff will precipitate out.

Reputation Comments on this post:

perfectly formulated answer

[sivoodoo]

swim would like to know the optimum starting temperature for CWE, does codeine degrade at high temps??

thanks

si

[Tortoise]

Captain Jack Sparrow beieves that the water doesn't need to be warm, this only helps that tablets dissolve faster. He only ever uses cold water and has sussed out which brands dissolve best. Never had a problem.

Play safe kids.

[erriksen]

SWIM always used warm water. Once SWIM tried it starting with cooler water (cold tap temperature) and seemed to have a better extraction. Flies in the face of what one might think, but anyway, SWIM uses cooler water now.

[LexaproHo]

Swim found that room temperature water was better than using warm/hot water in a CWE. Swim would just stir the solution for awhile and set in in the freezer for a short while to 4c and the whole process would take swim about 30 mins.

[Big Fella]

Biggles is known to use tap water, however when he reads this he may well change his practice.

[sunshine_buddy]

Sivoodoo-
Swim once boiled codeine in a pan and it didn't seem to degenerate at all. Swim thinks boiling water will be of no harm.

[Harry]

The best results SWIM has had in performing CWE's, has been by starting out using cold tap water, then bathing the bowl it was mixed in in warm water (a few inches of hot water sitting in the bottle of the sink) to speed up the dissolving process to about 20 mins, followed by about 20-25 mins of cooling in the freezer. Coffee filters used to pour into 2 separate cups, wrapped around the top of them. The whole process was less then an hour in total. And yes, very effective. Water amounts of 175 ml were used for 55, 8 mg otc acetaminophen based tablets.

Good Luck.