Stirring Bars Are Superstition? | Hacker News Reader

Stirring Bars Are Superstition?

science.org

2 pointsdcminter8 comments

the primary function is to quickly dissolve reactants rather than wait for passive dissolution to occur.

very few competent chemists would elect to commence a reaction, with a large amount of reactant still undissolved at the bottom of a vessel.

the stir bar is often left in, through the rest of the reaction.

But here's the money quote from Mr Lowe's take on the paper: "If you were presented with these data without being told that stirring was the variable under consideration, you’d have to conclude that whatever it was, it wasn’t really that important, honestly."

i.e. it doesn't necessarily speed it up or change the yield. So why do you care if the reactant's still on the bottom of the vessel in that case?

what is not being considered is the preparation often starts with a volume of reactant on the bottom of a vessel slowly dissolving according to physical soluability.

if you start a reaction like that without stirring, you will see a big difference in product yeild.

Not in fact true, or not as a general case, according to this paper, which is why this paper is interesting.

actually it is very true, the "study" concerned 326 reactions of all reactions available. if reactant is undissolved it is unavailable to the reaction, thus uncontributary to molar ratio.

this will limit yield, as well as creating an impromptu addition of a secondary quantity of reactant

this paper is qwackery, mr lowe demonstrates in this submission, a paucity regarding chemical reaction kinetics, and fails to cultivate a critical interpretation due to this lack of knowledge.

Ok, we're done here.

Anyone who has done any level of chemistry, including home chemistry, has observed how important stirring is to dissolution. If you just dump some ingredient into a container with solvent without stirring, you're going to end up with undissolved solids on the bottom covered by a heavy super-saturated solution. Over a long enough time with changes in temperature, or heating from below causing convection, you'll eventually end up with a uniform solution. But if you need the product for some purpose, waiting an arbitrary time maybe isn't the best plan.

I think you're talking past each other. From the article: "Because you pretty much always stir your reactions, even when all the components are in solution right from the start - right?" Dc is saying that people stir stuff because its not properly in solution yet, and then they just don't turn it off because there's no particular reason to. Maybe somebody who understands chemistry better than me can figure out how relevant the experimental procedures from the supplementary material are to this scenario, I can't really make good sense of them.

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