h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

When dissolving one substance into another, I've been told to start with a little of the solvent then add more.

Case in point: Cider vinegar & honey - in a glass of water.
I feel it's quicker to stir while dribbling water in, then fill up at the appropriate time...

Am I deluding myself?

Traveller in Time stirring not shaking
"Stirring the solution will definitely make it even distributed faster.

Do not really see the point as the two liquids will mix fast anyway. Trying to dissolve honey in water would be tougher, dripping the honey in the water while stirring should be faster then the other way around. "

Yes, I can't see as it will make much difference. Using hot water will make the process faster - and it will make the honey runnier too

I think the vinegar bit was a red herring, honey being the ingredient in question.

Hot water does, of course, work faster - but for immediate use it doesn't taste too good and the stuff's an acquired taste anyway (however, it does seem to work as a mild tonic).

My question was prompted by my days as a lab assistant, maybe it related to solids?

Thanks for your input.

Traveller in Time on top
"There is the issue about sirup. . .

If you take a glass of water and add some sirup it is while the average appreciation for the mixture is much better if you add water to a little sirup.

Still probably a matter of 'stirring the sirup' by adding the water while this does not happen the other way around.

I prefer black anyway. "

It seems extremely well established that in chemistry, you start with your proscribed amount of solvent, and then add solute - slowly! But we're not really talking about general chemistry, are we?

Eh no, take your solute amount, and add solvent...

If you want to dilute to a defined volume, you want to add the solvent in portions, and allow to reach room temperature before adding the final bit of solvent.

Many dissolutions are
1) endothermic (see what nice words I remember) meaning that heat is drawn from the environment in the dissolution process, the liquid turns cold, and the liquid will have a smaller volume when cold. If you dilute to the mark when cold, and leave to temperate, your solution will be too weak.
2) Exothermic, heat is generated, and the liquid gets warmer. If you dilute to the mark when warm, you will have to add some more solvent once it's cooled down, or your solution will be too strong.

Now, what this has to do with honey and vinegar, I don't know. But I generally try to solve the stuff in a little liquid, and add more later.

Nope, not safe. Don't try that with sulfuric acid or sodium hydroxide. You way want to not use the entire amont of solvent initially, but you definitinely don't want to pour solvent onto solute.

Yes, it now makes more sense. There was a red honey herring in there, too.

I think my recollection must have been in relation to exothermic reactions - diluting sulphuric acid *does* ring bells.

Thank you all. You may now play among yourselves until the next bell.

So does it matter if you add milk to a cup of tea, or put the milk in the cup first and then add the tea?

yes, but only if using very fine china tea service as putting the tea in first could cause it to crack.

Is that where that habit comes from? Nothing to do with how the tea and milk react to each other?

The practice came from the mills where the common people would use earthenwear mugs whitch had a tendency to explode,
covering all around with pottery shards and boiling tea,
when a hot liquid was poured directly into them,
addind the milk first stopped the shrapnel attacks

Taff
agent of kaos

I didn't know that.

kea i have an animation...http://www.bbc.co.uk/h2g2/oldblobs/996668.swf
made for dna himself no less !

best fishes....tod

Great animation Tm

But is it true?

so it seems we have two sources, one the poor people with their roughly made earthen ware mugs, and the other the posh people with their very fine paper thin china tea service. The problem is the same though, hot water causing it to crack. I have me doubts about the earthen ware though as the water wouldn't be boiling (not if the tea had been left to mash properly) and I really ain't too sure it would be hot enough even for the most delicate of china to crack.

Personally I thought the point with tea was that *boiling* water is needed to effectively extract the nice stuff out of tea leaves so if you put milk in first, this cools the water and so impairs the quality of the drink.

But I don't know the facts, that's just what hootoo's own article says and I, for one, believe everything the edited guide says

yes, but you don't mix the tea and boiling water in the cup, do you? Well, maybe nowadays with teabags but back then (edwardian times I guess?) they didn't, twas done in a teapot. So by the time it hit the cup it wouldn't be boiling.

Ah, but I was thinking of dissolving salts and other solids, mainly...

Very true, though, that when you dilute (not dissolve ) acids and bases, you begin with a nice amount of water, and add the acid/base in small portions. Big safety aspect there. Since the water will come to an instant boil if added to acid, it will splatter hot acid everywhere.