Fyndium
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Powder addition?
What are good methods to add powders into reactions? There are powder addition funnels with screw to add precise amounts at a time, but if one is not
available for use, what are alternatives?
I just recently performed a reaction which I first dumped the powder into the reaction vessel and then added water and dropped in the reactant. The
powder formed a solid cake which took some serious effort to break, and it took half an eternity to react because of the reduced surface area. It
works this way, with the glitches, but it is quite inconvenient.
Second issue is the possible toxicity of a powder which asks for minimizing the handling time. Next to that, some powders may be hygroscopic. Also,
when adding a liquid to a powder, there is the issue of localized heating which can churn out side reactions, an issue which is easily solved in a
stirred solution which buffers heat gradients very efficiently when a solid is added in controlled manner.
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Herr Haber
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The instructions are on the back of the soup envelope 
Cant you add water, stirring then your powder instead ?
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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karlos³
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I thought it is weird to add water to a powder, isn't it usually almost always preferable to add a powder to the water/liquid, ideally under stirring?
It won't form a cake in this case for example, and I would say is in general the better choice.
Isn't it also like this on those powder soup envelopes or any of the other similar powdery things like this?
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Corrosive Joeseph
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It has been my experience to always says add water to powder, especially for like a packet soup..... Or cement.
This reminds me of an old girlfriend I once had.... Every time she would read the back of the packet, but still manage to do it backwards. She would
put a pint of cold water into a saucepan and then throw a whole packet of soup into it and every time without fail, it would be as lumpy as she was.
Of course, my way worked better but there was no talking to her.... Measure out the pint of water into a measuring jug or whatever..... Place the soup
powder into the saucepan.... Now add a few drops of water to wet the powder and stir like crazy.... Add a few more drops, and when the powder turns
into a nice wet paste.... Slowly continue to add all the water and it will mix much better.... With no lumps!
Keep in mind, she definitely did not have a hotplate stirrer but this worked for soup every time.
/CJ
Being well adjusted to a sick society is no measure of one's mental health
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karlos³
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They must have different binders in your country, I can't remember I ever was in a "add water to powder"-situation, it was always the other way
around?
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Corrosive Joeseph
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Not even when you do something as simple as make a cup of instant coffee....? That's a pretty good example of it.
It just doesn't taste the same when you pour hot water and throw coffee on top. Ever forget to put the coffee in the cup....?
Of course it does work the other way around but soup girl just wasn't getting it. It also seems to take ages to mix powder into anything wet though. I
suppose things like strong stirring, slow addition and hot solvent help, but for mixing cold water and powder, my preferred way is definitely how I
described.
/CJ
Being well adjusted to a sick society is no measure of one's mental health
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Fyndium
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For matter of food, the instant noodle packs just call to add boiling water because they are the consuming vessel itself. It is more convenient for
dry food to boil the water in the stovepot and then add the powder, not make a mess with a third container.
But my point was that if a powder is too dusty and toxic. Powder addition funnel is probably then only good method.
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Herr Haber
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Dont you get lumpy food that way ? You'd have to beat the mix with a whip or a fork pretty hard otherwise.
I try to avoid scraping my teflon or luxury (130E!) steel pot if possible.
Your coffee example reminded me that I soon learned it was more fun to add just a little bit of milk to a whole lot of chocolate powder than the other
way around.
Yay, chocolate paste. You've all done it
But as for your problem Fyndium,
If whatever you want to add is soluble in water why dont you just add as a solution ? Your other solid is water soluble. You mentioned overheating so
perheaps I'm not seing the big picture.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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monolithic
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I typically add through the unused neck of my flask. The "professional" solution to this problem would be a powder addition funnel but they're quite
expensive ($250-500) and they don't seem to pop up very often on eBay, much less at a reasonable price. If you have money to burn, Chemglass and Ace
make them.
[Edited on 10-11-2020 by monolithic]
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valeg96
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An unusual way, good for small amounts and in environments that are not too vigorously stirred is weighing the solid in the cut bottom of a GC vial
(or generic glass 1 mL vial) which is then dropped into the flask by a side neck. Clean addition, and the glass piece is recovered at the end. This is
a technique used, for example, during voltammetric measurements in glass cells with plenty of electrodes where you mustn't spread the solid analyte
onto necks and electrodes or lose it like when it spreads on a funnel.
[Edited on 11-10-2020 by valeg96]
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Texium
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Those powder addition funnels are rarely used by professionals either. Apparently they don’t work as well as they would seem to, and they’re
extremely difficult to clean. I’ve never seen one used in a university lab before, at any rate.
Generally it’s just dump it in the unused neck of the flask if you can, and if you’re working air free then you’ll need to get it into a
solution somehow and add it with a syringe or cannula, or manipulate your order of addition so that it’s the first thing you add to the flask before
you evacuate it.
Edit: and as for ramen noodles, I stir the packet in after the noodles are cooked, and I’ve never had it be the least bit lumpy. I think it really
does depend on the water temperature. If it’s hot, add powder to water. If it’s cold, the other way around would work better.
[Edited on 10-11-2020 by Texium (zts16)]
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Fyndium
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I faced this issue with lead oxide, which is both toxic, dusty and insoluble in anything. I just measured it directly in the reaction vessel, added
some water and concluded that it formed a glue-like gunk, and just dumped in GAA and let it react until magstir started to work, and after that, it
takes few hours for all to dissolve at 60C.
An unique situation, but the dust issue was the major culprit in here. It is such a compound which one just doesn't want to have dust anywhere around.
I wanted to keep the system enclosed as much as possible, and thought that gradually adding it by spoonful would likely cause it to get boring, which
increases risk of spilling the powder.
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Panache
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there are two ways that require no special equipment
balloon.
weigh your powder into a ballooon, put the end of the balloon over a spare port, then as it required add powder by lifting the baaallllooon and
feeding it down.
if for some reason your reagent is a powerful anti-ballllooon super-reagent, then you can rig up this device, you will need one 60 degree female to
male bend and one 60 male to male bend, the same size as your port and a round bottom,
or a two necked round bottom and one 60 male to male bend. a large rubber band is also of use
basically weigh your powder into the round bottom attach the two bends attach this train to the reaction flask spare port, tie all together with the
rubber band, the powder can now be added through manipulation of the bends. You will get the hang of it. Helps if you were formerly an architect or a
aerial snowsports enthusiast. Once you get it working this method is fantastic, as your entire setup is sealed and glass based.
The ballon trick is also very good. alwags first turn the ballon inside out as the inside has talc typically on used as mould release agent.
and in relation to powder to water. lets ask Dr Oekter (i think i got that right, its like a german brand of instant things like custard, jellies etc.
the custard was great, im going to order online its been years....
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Fyndium
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Ah, the great hive mind always helps out. The balloon method actually sounds brilliant. It can also be filled directly from a container without
dusting. The joint method needs a little more looking into.
Those balloons, always helping out if you need gas or powder.
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teodor
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What is your source of the lead oxide by the way?
I plan to make some PbAc2 for some experiments which I hope I will be able to share but my source of Pb is usually PbCl2 which could be easily
converted to hydrated lead oxide which was observed as compound with nice consistency.
[Edited on 12-10-2020 by teodor]
[Edited on 12-10-2020 by teodor]
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