Yield or Time?

[G.Patton]

Hello there! During chemical syntheses there are residues of target products. They are formed due to some manipulations like washing, layer separation, decantation, acidification (salt formation) and so one. Such products can be collected by additional extractions, distillations and crystallizations in order to increase synthesis yield insignificantly. These manipulations take some time and increase whole synthesis process. In addition, it takes more time in laboratory, which is connected with potential stealth risks.

UPD
There is loses in a sludge of some popular syntheses:​

• Methamphetamine Synthesis From P2P Via Al/Hg​

The yield without additional sludge washing was 4.5 g, or 65% of the theoretical yield.
The loss in the sludge is 0.5 g, or 7.2%.

 

[Heineken]

if u know how to made then time is no problem.
if u made 3/4mmc 3/4cmc apvp/bkndma 20kg or 100kg is max 2days made powder 2max weeks made crystal

 

[Frit Buchner]

This topic I wouldn't call 15% insignificant. I guess maybe in Poland where the precursors flow like water down the street, but those of us who's butthole stays puckered for a week while hoping our mail reaches the box, are going to want to collect that 15%. If I have to buy plastic weld for $40/pint and distill the DCM out if it, I'm going to want to recover it. If I can buy a liter for $30, I'll probably leave it behind.

 

[Mr Gonzo]

I 2nd the opinion that 15% is a waste of effort, time and money. Seeing the reaction rating being the way it is. 67.1% of people are really scrapping the bottom of a barrel in my opinion, after performing synthesis's and doing extractions etc, personally 15% is nothing when the first re crystallization can lower yields in your product by at least 20 to 35% easily maybe more!

 

[PNicole]

It depends. Dealing with sludge, no way is it worth it. Even in legal industries, sludge is one of the most difficult things to deal with. In the original write up, he is only using 5ml of 25% NaOH solution. You need around 9-9.3 grams of NaOH to destroy each gram of Al. So around 54-55 grams of NaoH (100%), I promise you there wont be much of a sludge left.

Also 65% is very low yielding, there are better tweaks to this method. Methanol is far superior, Al grains never foil and a better Al / Hg ratio.

 

[SoldadoDeDrogas]

I can see where this depends. Right now, I'm scraping the bottom for every cent at higher risk. Optimally, I would prefer reduction in time and labor, if you want increased yield, just scale up.
In the case where it's not the general procedure itself, but a matter of choice of taking a moment to do a 2nd or 3rd wash and it can only be done then and there, I'm for it. I am constantly looking for shortcuts and multitasking - for example, if you can keep going and put something on the backburner, then go back and re wash and then add that back to the experiment in progress. Or add your re-washes/extractions to your recycling pile - or your 'sludge'.
In the case of recycling sludge - save up 10 or 20 rounds and do it all at once in your down time, or when things get tight. Small amounts of product will be lost to washing and purifying, but the overall yield isn't effected terribly. The overall weight, however, is effected due to loss of impurities, which I am all for. Priority goes from safety to quality and then efficiency and minimizing loss, atleast for me.