pitch drop experiment at the college of Queensland, Australia. Picture licensed under CC BY-SA 3.0.

You are watching: Which liquid is the most viscous?

Viscosity is a measure of exactly how strongly a liquid resists steady deformation. Fluids with greater viscosity such together honey room thought of as “thicker” than less viscous fluids favor water. The selection of viscosities in liquids is enormous. Superfluids, such as Helium-II, have zero viscosity. Honey is between 2,000 and 10,000 times much more viscous 보다 water. Part fluids are so viscous they show up to it is in solid and also yet, over time, slowly flow.

among the many viscous liquids recognized is pitch, additionally known together bitumen, asphalt, or tar. Demonstrating the flow and also measuring that viscosity is the topic of the longest continuously running clinical experiment, started in 1927 in ~ the college of Queensland in Australia. Prof. Cutting board Parnell heated pitch (which dramatically decreases its viscosity), climate poured it right into a funnel with a sealed bottom. After 3 years (to permit the pitch to settle), the bottom of the funnel was removed and the funnel inserted in a bell jar v a beaker listed below it. The pitch progressively flows the end of the funnel, developing a huge drop. Around every decade a drop falls off into the beaker.

While each drop bring away a decade to form, it just takes about a tenth of a 2nd to fall. In the 89 years the experiment has actually been running, nine drops have fallen so far. Nobody has actually yet it was observed a drop falling. Since the 1990s the experiment has been continuously monitored by a net camera, however when the eighth drop fell in November 2000 the camera to be offline and also the occasion was not recorded. In April 2014 the 9th drop was broken off while replacing the beaker in ~ the funnel, which had been filled sufficiently by vault drops to interfere through the experiment. Over there is a web site dedicated to watching for the tenth drop come fall.

from the rate of circulation over the expression of the experiment, it has actually been approximated that the key in the funnel has a viscosity 230 billion times higher than water. It is estimated that sufficient pitch stays in the funnel because that the experiment to continue for an additional century.

below is a time-lapse video of the descent of the 9th drop and also the developing of the tenth drop spanning the period from April 2012 through April 2015.

This chemistry Heritage foundation video has a summary of the experiment by its long term custodian, the so late Prof. John Mainstone.

A pitch drop experiment was started at Trinity university in Dublin, Ireland in 1944. The experiment laid forgotten on a shelf for years as number of drops formed and fell. In April of 2013, as another drop to be forming, a web camera was set up to repeatedly monitor the experiment, and on July 11, 2022 the drop was observed to fall, the very first time such an event had been recorded. Here is a news report native RTE around the experiment showing the drop falling.

below is the full time-lapse of the Dublin drop falling.

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If you"ve reached that phase of life where the heart-pounding excitement of watching repaint dry is too lot to take, it"s straightforward to set up your very own pitch autumn experiment. Every you require is a glass funnel and some key (you have the right to buy high-grade optical pitch from GotGrit.com). I"d put a rubber stopper in the bottom of the funnel to originally seal it. Warmth the key gently on a range until the pours quickly (use a disposable pan, because you"ll never be able to remove every the pitch), then pour it right into the funnel. Wait a couple of weeks till the pitch has totally cooled, then eliminate the stopper, set the funnel ~ above a stand with something to catch the eventual drops, and away girlfriend go. Pitch comes in various grades ranked by “hardness” (actually, viscosity), and also it"s far better to select one of the softer (lower numbered) grades. A pitch drop experiment to be reportedly started Aberystwyth college in Wales in 1914, yet to date has yet to create a single drop.