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Every morning I wonder: “Will the sugar mix more quickly if I stir it in with the usual circular stroke, or is it more efficient and quicker to randomly agitate it?”
I never really asked why this is interesting to me, but it is. There’s no way to test this without some apparatus so here’s my take
on it. If you are science-literate please chime in.
Using a laser shining through the filled vessel one can determine the presence and degree of particulate matter (PPM). I have a water filter that leaves no particulate matter behind. BUT sugar is not a particulate as it dissolves, so what could be done? The tester for this unit uses conductivity in the water.
Could conductivity be used to answer my question? With anything you wanted to dissolve?
I noticed that if I continued to lightly strike the lip of a crystal glass filled with coffee, the note changed as the sugar went into solution, deepening as the dissolution progressed. If calibrated to the vessel of the moment in the A/B test of “CIrcle or Scribble” strokes you should be able to tell if one is faster than the other. Maybe not. But then…
½ the answer
https://chem.libret..._Rate_of_Dissolving
Mechanics, but no way to A/B test for speed [minoradjustments, Jan 03 2024]
hot chocolate effect
https://www.youtube..._channel=SteveMould
that coffee mug striking rising pitch thing [Loris, Jan 03 2024]
Erythritol and blood clots
https://www.nature..../s41591-023-02223-9
[bs0u0155, Jan 05 2024]
[link]
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Maybe not that important, but I learned recently that the rising pitch thing is called the hot chocolate effect. Reportedly due to air-bubbles, although both explanations I've seen felt a bit unsatisfactory. |
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Anyway, apparently it's repeatable, so presumably not related to sugar going into solution. |
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//Every morning I wonder: “Will the sugar mix more quickly if I stir it in with the usual circular stroke, or is it more efficient and quicker to randomly agitate it?”// |
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A friend of mine is a researcher in chemical engineering. For obvious reasons, they mix stuff a lot. He points out that stirring is a bloody awful way of mixing most things. Although, it is cheap and easy. There's lots of strategies that work more efficiently, bubble mixing is one, another involves injecting two liquids to the middle of closely apposed counter rotating discs. |
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//Using a laser shining through the filled vessel one can determine the presence and degree of particulate matter (PPM)..... BUT sugar is not a particulate as it dissolves, so what could be done? The tester for this unit uses conductivity in the water. |
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Could conductivity be used to answer my question? With anything you wanted to dissolve?// |
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Lasers, or any light really, pass straight through many liquids. Particulates can block this and you can use the light attenuation as a measure of particulate concentration. This is pretty crude however. A better system is to shine light through your liquid sample and collect light that transmits through the liquid AND light that is scattered sideways. This allows you to assess particles that are relatively clear, but that have different refractive indices to the liquid, like sucrose crystals in water. |
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Conductivity is a different beast, you need to know something about the liquid, particles and effects of dissolution. Undissolved sugar in PURE water won't be detectable. Sugar is a very poor conductor, and so is PURE water. Throw a tiny amount of dissolved salts in the water, like with tap water, and the conductivity shoots WAY up, now the undissolved sugar will REDUCE the conductivity of the water it's in. |
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It can work the other way around too, like with conductive metal particles in non-conductive engine oil. |
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//I noticed that if I continued to lightly strike the lip of a crystal glass filled with coffee, the note changed as the sugar went into solution, deepening as the dissolution progressed.// |
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Two things are happening here. 1. The sugar is dissolving into the water. If something dissolves, the volume of the solution vs original solvent is the same. So the sugar has increased the mass & density of the coffee/tea. More massive things resonate with a lower frequency, while less massive things resonate with a higher frequency, like when you fill your larynx/trachea with helium and sing some Bee Gees for comedy effect. |
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2. Dissolving things is often endothermic, meaning the sugar dissolving into coffee/tea is making it slightly colder. Colder things are denser, see #1. |
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If you want to solve your problem, preparation is your friend. Simple syrup is 1:1 (by volume) of sugar and water, so 1 teaspoon of simple syrup contains 1 teaspoon of sugar AND 1 teaspoon of water in a total volume of 1 teaspoon, an example of 1+1 = 1, if you like. Anyhow, the energetically expensive part of deconstructing the solid phase sucrose crystals into monomolecular sucrose in water is done ahead of time. So adding the syrup to the coffee/tea is just lowering the concentration, much faster. |
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You could also use more finely ground sugar, but you might want to adjust volume, finer crystals pack better, so often have increased density. |
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Anyhow, an easy method of testing: |
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Take two coffee filters, weigh them, write the weights on the filters. |
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Pre-weigh two identical portions of sugar. Dump each into a set volume of water (go with cold, it will slow the whole assay down and make more controllable) and stir/scribble for a set amount of time. You want to tune the amount of time so that about 1/2 the sugar dissolves, a glass will help you see this happen. Then dump each through the coffee filter, collect the flow-through and dry the coffee filters overnight at >100C. Then weigh each filter to determine which has more sugar left over. Weigh the flow through also, the mass in the coffee filters + the extra mass in the water should add up to the mass of sugar poured in. |
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If you want to push the boat out, do several time points and plot the reciprocal of the sugar weight vs time. You'll end up with two curves, probably exponential, that will allow you to determine the rate (in g/litre/s-1) of the two methods. Finish with a garnish of statistics to work out if there's any meaningful difference. |
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Excellent description of experimental setup, [bs0u0155] |
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I suggest using a pantograph type machine for repeatable stir and scribble patterns. |
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Ask and ye shall receive. Thanks. I knew someone here could pick this apart. The changing tone seemed so elegant but very hard to quantify. I didn’t think circular stirring was the best mixing method and the chemical engineer verified that. I like the filter solution; very straightforward, repeatable. Thanks again, all. |
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Can you measure the amount of sugar dissolved in water by shining a laser through the water at an angle and measuring the refractive index of the liquid? (i.e. Does dissolved sugar change water's refractive index?). If so, then it would be nice to shine a laser through a container of water as you add sugar, and as you stir it in, to watch the refractive index change in real time. |
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//The changing tone seemed so elegant but very hard to quantify.// |
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If you can hear it, you can measure it easily. Just a microphone and simple audio software like Audacity* you could clank your spoon against the side of the glass in a regular pattern as the sugar dissolves and plot the frequencies vs time. Then after the fact, or before, experimenter's choice, fully dissolve known amounts of sugar in the same volume of water at the same temperature etc. clank the glass at each sugar concentration from 0 to really-quite-a-lot of sugar. Then you can pull the frequencies from each one and plot a graph of sound frequency in Hertz, vs sugar concentration in g/l. Then you have another working assay. |
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//Can you measure the amount of sugar dissolved in water by shining a laser through the water at an angle and measuring the refractive index of the liquid?// |
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Sure. The problem with refractive index is that it doesn't change a LOT in response to small changes in solute concentrations. This is the interesting part about designing methods to measure things. Maybe if you were an expert who's really set up to measure refractive index, great. Personally, I wouldn't choose an assay that only moves a few percent and that is very sensitive to movement, temperature etc. in a stirring/turbulent environment. |
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*This actually has a really nice and unexpectedly advanced FFT (Fast Fourier Transform) feature for pulling frequency data. |
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Nobody wants to guess at this, so it’s a good experimental subject. My completely non-experimental subjective take is that when I randomly ‘scribble’ sugar into my cup of coffee it dissolves faster (marginally) than if I circle. I just think of the violence at the sugar grain level; being bashed around every which way with coffee eating away on every side, while circular stirring is so linear, with all your fellow sugar crystals swimming along in laminar flow, peacefully dissolving. |
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Of course the other way to think about this is that coffee without sugar is much nicer, get good beans and god equipment and develop a taste for unsweetened beverages. |
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//I randomly ‘scribble’ sugar into my cup of coffee it dissolves faster (marginally) than if I circle.// |
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Probably. There's also the centrifugal force of a conventional stir. Sugar being denser than coffee means it will be flung to the periphery. There it will dissolve, but, coffee with sugar in it will be denser and also flung to the periphery. So you have a situation where you're trying to dissolve sugar crystals into the coffee that is already enriched in sugar. |
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//while circular stirring is so linear,// |
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There's an Einstein space-time coffee gag in there somewhere. |
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//coffee without sugar is much nicer, get good beans and god equipment and develop a taste for unsweetened beverages.// |
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Coffee is a weird drink. There's a million people arguing online about the best way to make it. Personally, every now and then, I get an amazing cup of coffee. Then, I can't replicate it. Some I've made myself, some I bought in fancy places. I try to make the same coffee with the same beans, equipment and water.. no. Same coffee shop, same person, no. I weened myself off sugar in coffee and tea 20 years ago, not out of some high-minded principle, just laziness. If I didn't need sugar, then there's one fewer necessary ingredient and an increased likelihood of getting a reasonable drink. I wouldn't deign to tell anyone how they like their coffee however, because there's always a better answer, apparently. Sometimes, coffee is just a tool, the original energy drink, and a little sugar can't hurt that. |
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Maybe stay away from the sugar alcohol sweeteners however, looks like they're causing heart attacks. <link> |
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//coffee without sugar is nicer// |
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I use sugar. Call the coffee police. I get the best high mountain-grown, small holding, Puerto Rican Arabica that I’ll put up against any top level bean on the planet. I grind them every morning, 20 grams per 8.5 oz cup. I just prefer a little sugar; I think it brings out flavors in the coffee that are hidden otherwise. Bad beans make bad coffee, period, sugar or not. |
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And linear stirring is so circular… |
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liquid-liquid mixing is optimized in turbulent flow, so I like to get a circular vortex going, switch directions to induce turbulence and repeat until satisfied. |
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Note: this only applied to liquid-liquid mixing. The dissolution kinetics on the liquid-solid interface at the sugar crystal are only affected in that the average concentration of sugar at the external barrier layer should be lowered with better mixing and therefore dissolution rate will also increase. |
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