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Showing posts from December 24, 2018

ajax FormData upload - multiple progress events in Chrome and Firefox, only one in Safari?

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up vote 0 down vote favorite **EDIT: does work in Firefox I am just starting to work with submitting forms through XMLHttpRequest . I enhanced a standard form to submit this way, based on code found on this site and in other tutorials. The form includes a file input, and the enhancement is intended to display the upload percentage (as text and a progress bar). This works perfectly in Chrome and Firefox, but in Safari it seems like the progress event only fires once, at the beginning of the upload. The form submission does go through correctly, but the percentage stays close to 0% until the upload is finished. Is there some trick to doing this in Safari? I've been searching for hours and cannot find any special instructions. I've tried demos of progress bar code and all seem to work properly in Safari. I am thinking now ...

In a saturated solution, why is there ongoing dissolution and crystallisation?

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up vote 7 down vote favorite I was studying equilibrium, and had this question.. In a saturated solution with sugar dissolved, why is there a constant process of dissolving and crystallising? What I mean by this is, why don't the already dissolved sugar just stay that way, and the excess undissolved sugar stay that way? As I thought this would seem easier, and neater (?), wouldn't it?? Is it because the undissolved sugar is still in water, and that means it will want to dissolve, but since the solvent has reached maximum amount of solutes it has to kick some sugar out and hence there is a process of crystalisation?? I am sorry for a rather stupid question... But any explanation is much, much appreciated... equilibrium ...