precipitate should not change while draining solution

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This issue was reported by @phet-steele in https://github.com/phetsims/beers-law-lab/issues/154#issuecomment-221085463.

@pixelzoom the precipitateAmountProperty is calculated over and over again while draining a solution. The value fluctuates up and down, causing the visual effect of precipitate appearing and disappearing while draining. The capture rate on this video is lower than I'd like, so it's not as dramatic looking:

[pixelzoom]

This issue sounds very familiar, like something I fixed long ago. And in fact it does not occur in release 1.2.3 (http://www.colorado.edu/physics/phet/dev/html/beers-law-lab/1.2.3/beers-law-lab_en.html). It does occur in 1.3.0. Is it possible that this may have been (re)introduced by PhET-iO instrumentation?

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The issue I was thinking of is https://github.com/phetsims/concentration/issues/1 (Flickering particles when solution from dropper is added to a "Saturated!" beaker).

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Now I'm not so sure that I'm reproducing this reliability, so it may be something that was present in 1.2.3. I'm also wondering it's demonstrable for other solutes, or just for "Potassium permanganate".

[pixelzoom]

@phet-steele, a few questions....

(1) Can you reproduce the problem with either of these older versions? http://www.colorado.edu/physics/phet/dev/html/beers-law-lab/1.2.3/ http://www.colorado.edu/physics/phet/dev/html/beers-law-lab/1.3.0/beers-law-lab_en.html

(2) Is the problem reproducible with other solutes? just with "Potassium permanganate"? or more noticeable with "Potassium permanganate"? I'm wordering if this occurs mainly for solutes with low saturation points.

(3) What platform did you observer this on? And does it also occur on other platforms?

[phet-steele]

1. 1.2.3 NO, 1.3.0 YES
2. Doable on all, easiest for me to duplicate on KMnO4 just because it's quicker (low saturation point)
3. Win 10 chrome and OSX 10.11.5 Chrome

[pixelzoom]

@ariel-phet Should this be addressed for 1.4.0 release? It's not immediately apparent why this problem reappeared in 1.3.x, but it was present in 1.3.x, so is not technically a new problem. If this issue needs to be addressed for 1.4.0, then that will push 1.4.0 release out into August (given the other things on my plate). If this issue is deferred, then 1.4.0 release can likely happen sometime in the next week. My recommendation is to defer.

[ariel-phet]

Since not a new problem (and since now summer), I concur to defer, but lets plan on patching after function builder goals are met.

[pixelzoom]

@ariel-phet said:

lets plan on patching after function builder goals are met.

It's now long after function-builder goals were met. So I will self assign and look at this when I have time.

[pixelzoom]

@phet-steele Could you please test this in master and see if it's still a problem? I can't seem to reproduce it anymore, wondering if was corrected by some other change (which would be disconcerting.)

[phet-steele]

Could you please test this in master and see if it's still a problem?

I cannot see it in master.

[pixelzoom]

Well, the problem is apparently gone. I see nothing obvious in the commit history that might have fixed it, mostly lots of PhET-iO commits that I don't recognize. Since I can't identify the fix, I can't patch a maintenance release. So this fix will need to wait for the next release branch (1.7).

[pixelzoom]

Marked as fixed-pending-testing for the next RC cycle.

[pixelzoom]

This problem has resurfaced. In https://github.com/phetsims/beers-law-lab/issues/238#issue-436825355, @KatieWoe reported:

Test device: Dell Operating System: Win 10 Browser: Chrome Problem description: Minor bug found in https://github.com/phetsims/QA/issues/309. When there are a smaller number of particles sitting at the bottom of a saturated solution, draining the solution causes some of the particles to move along the bottom wildly until draining stops. Seen in older versions, so not connected to the above release. Steps to reproduce:

1. Select a solute and add it until you have a saturated solution with particles on the bottom
2. If there are too many particles, use the dropper to dilute it until you have a smaller number
3. Drain some of the solution and watch the particle behavior

Screenshots:

Troubleshooting information (do not edit):

Name: ‪Concentration‬ URL: https://phet.colorado.edu/sims/html/concentration/latest/concentration_en.html Version: 1.3.13 2019-04-22 08:50:58 UTC Features missing: touch Flags: pixelRatioScaling User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.103 Safari/537.36 Language: en-US Window: 1536x722 Pixel Ratio: 2.5/1 WebGL: WebGL 1.0 (OpenGL ES 2.0 Chromium) GLSL: WebGL GLSL ES 1.0 (OpenGL ES GLSL ES 1.0 Chromium) Vendor: WebKit (WebKit WebGL) Vertex: attribs: 16 varying: 30 uniform: 4096 Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32) Max viewport: 16384x16384 OES_texture_float: true Dependencies JSON: {"assert":{"sha":"7d27130a","branch":"HEAD"},"axon":{"sha":"9bf8f88c","branch":"HEAD"},"babel":{"sha":"735d57d7","branch":"master"},"beers-law-lab":{"sha":"10281f45","branch":"HEAD"},"brand":{"sha":"b040cac5","branch":"HEAD"},"chipper":{"sha":"0ebc6913","branch":"HEAD"},"concentration":{"sha":"b4e5af61","branch":"HEAD"},"dot":{"sha":"04efe0bc","branch":"HEAD"},"joist":{"sha":"a9ad0567","branch":"HEAD"},"kite":{"sha":"dce9765e","branch":"HEAD"},"nitroglycerin":{"sha":"ad3cb990","branch":"HEAD"},"phet-core":{"sha":"c48bf320","branch":"HEAD"},"phetcommon":{"sha":"3a85ef86","branch":"HEAD"},"phetmarks":{"sha":"3fdfece0","branch":"HEAD"},"scenery":{"sha":"864e3a56","branch":"HEAD"},"scenery-phet":{"sha":"2b60b8e4","branch":"HEAD"},"sherpa":{"sha":"e90b735f","branch":"HEAD"},"sun":{"sha":"6f66368f","branch":"HEAD"},"tandem":{"sha":"29f64233","branch":"HEAD"}}

[pixelzoom]

The steps in https://github.com/phetsims/beers-law-lab/issues/175#issuecomment-486355881 are easier/quicker to follow if you use the shaker instead of the dropper. That said...

I've been unable to reproduce this in master, but I'll try again. If I do manage to reproduce it, the easiest way to address it might be to recompute the amount of precipitate only when the volume is constant or increasing, or when the "Remove Solute" button is pressed.

[pixelzoom]

I cannot reproduce in master. And I just noticed that https://github.com/phetsims/beers-law-lab/issues/175#issuecomment-486355881 says:

Seen in older versions, so not connected to the above release.

So this was fixed, and appears to still be fixed. Closing.