For example, if a wizard were to dissolve some sugar in a bowl of water, or absorb some water into a sponge, or make some cake batter, could that wizard then Summon ONLY the sugar from the solution, the water from the sponge, or any specific ingredient from the cake batter but leave behind the water/sponge/batter?

  • Wouldn't the case of the sugar water be similar to the brains in the tank, just on a smaller scale? If we look at it like that, then yes it is possible. It should work in almost all cases as we have seen in OotP that it is possible to summon something that is suspended in a fluid. During the department of mysteries struggle we see that ron was able to summon a brain that was suspended in a tank of fluid. – CBredlow Feb 10 '16 at 22:38
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    @CBredlow Maybe, but who know how precise this would be. Theoretically, your logic is not flawed, but practically...I'll have to try it out. – CHEESE Feb 10 '16 at 22:50
  • This has made me curious, so I made a related question about how small you can go. If I get an answer from that, then I'll convert my comment into an answer using evidence from my question. – CBredlow Feb 10 '16 at 22:52
  • @CHEESE I suppose it is derived from my question.. I was going to ask that :D.... – prakhar londhe Feb 11 '16 at 8:09

I don't think Accio charm can be used to change chemical composition of different substances e.g. a solution of sugar and water.

My reasons are following:

In Half blood Prince's chapter "Birthday surprises", we come across the following activity of antidote making when Slughorn says:

"... which means, of course, that assuming we have achieved correct identification of the potion's ingredients by Scarpin's Revelaspell, our primary aim is not the relatively simple one of selecting antidotes to those ingredients in and of themselves, but to find that added component which will, by an almost alchemical process, transform these disparate elements--"

  1. If Accio spell could work that way, instead of distilling different elements from the concoction, students would have just said "Accio [ingredient name]", measure their quantities right away to form an antidote. Of course always assuming that they would already know the ingredients using revealing charm. (Though vague commands did work too, like Harry saying "Accio Horcrux" instead of "Accio Slytherin's locket").

  2. When hermione's Polyjuice potion went wrong in Chamber of Secrets, she could have just pointed her wand at herself and said "Accio Polyjuice poition" and wham, Poly juice potion would have been removed from her blood and system

  3. When Arthur Weasley got attacked by Nagini in Order of the Phoenix, Healers at St. Mungo's could just use accio charm to extract the poison from his body immediately.

  • for one thing, Accio charm was far too advanced for a second year... – prakhar londhe Feb 11 '16 at 8:10
  • So was the poly-juice poition @prakharlondhe. Anyhow my premise isn't solely based on that one example. – Aegon Feb 11 '16 at 8:41
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    I would also assume that Accio's threshold for bonds is very, very low. Otherwise it would make for a killing curse on par with Avada Kedavra with some serious Crucio mixed in. "Accio skull!" - no thanks. – Misha R Feb 11 '16 at 9:06
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    There's also the dragon's blood Slughorn uses - he siphons it up, but it's dusty - which suggests that things can't be unmixed. Dust doesn't dissolve, usually, and can be visibly seen - but it seems like it can't be removed via magic any better than we can without it, ie, by picking it off or skimming it out. Something that is mixed or dissolved in is probably equally inaccessible. – Megha Feb 11 '16 at 13:29
  • Forcibly removing a liquid from your system seems like it would be bad for you. As in, burst blood vessels bad. – user867 Feb 12 '16 at 5:01

Every instance of the Summoning Charm is used on a discrete and tangible item - broom(s), books, brain etc. While the instructions might be somewhat vague ("Accio Firebolt" knows enough during Goblet of Fire to realise that it needs to bring the caster's Firebolt, while theoretically Harry could have used it in an instance where he was summoning someone else's with the same words, his intent was clear enough).

Separating a solution is an entirely different concept. You're not only talking about something that a person cannot easily visualise, the reality of how it would work is that you would need to remove every particle of a substance from another substance. That renders it fundamentally different from removing a visible brain from a tank of water. Even if you could convey the intent, it's unlikely that you could ever do it perfectly unless you were dealing with two substances that are already discretely separate, and maybe not even then (chemistry and physics being what it is).

Consider this too - do you expect the brain that Ron summoned was completely dry? Or that by summoning his broom, Harry coincidentally removed all the dust, stains, etc. that might have been on it in its original location at the same time? There's no evidence to suggest that is how the spell works, and it would need to work that way to have the effect you're asking about.

  • I think it's not impossible in theory, but it is simply too hard for anyone to achieve because it's so complex. Ultimately the words don't matter much, they only serve to focus the intent (as shown by the existence of equally powerful, but harder to achieve, nonverbal spells). (Unfinished, continuing) – Pwassonne Feb 14 '16 at 22:22
  • What Accio does is, it moves a determined bunch of matter towards the caster. What gets moved or not is decided by the caster's intention. Separating a solution would be the same thing on a much smaller scale, that of molecules. It could be done in theory, but it would probably require much greater focus and mental capability than most people have, and I don't suppose it could be done perfectly. It would involve Summoning a very large number of very small items – Pwassonne Feb 14 '16 at 22:31
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    Well, it moved a determined object in every example given, where the caster can make a concrete distinction of what the object is. Arguably, one valid distinction demonstrable can be the ability to visualise the object that you're attempting to summon (I think that's held true throughout). Maybe you have seen what molecules through a microscope in the past, and that can make it work? Also to note: summoning moves the object from one place to you, nothing more. If you summoned a broom through water, it would presumably get wet. Sugar through water might just bring the water with it. – DariM Feb 15 '16 at 3:47
  • Yes, it might bring some of the water, so no perfect unmixing. – Pwassonne Feb 15 '16 at 8:51

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