key drop experiment in ~ the university of Queensland, Australia. Image licensed under CC BY-SA 3.0.

You are watching: Which liquid is the most viscous?

Viscosity is a measure up of exactly how strongly a fluid resists progressive deformation. Fluids with greater viscosity such as honey space thought of together “thicker” than less viscous fluids like water. The range of viscosities in liquids is enormous. Superfluids, such as Helium-II, have actually zero viscosity. Love husband is between 2,000 and 10,000 times much more viscous than water. Some fluids space so viscous they appear to be solid and also yet, end time, slowly flow.

among the many viscous liquids recognized is pitch, also known as bitumen, asphalt, or tar. Demonstrating that flow and measuring that viscosity is the topic of the longest consistently running scientific experiment, begun in 1927 in ~ the college of Queensland in Australia. Prof. Thomas Parnell heated pitch (which drastically decreases its viscosity), climate poured it right into a funnel through a sealed bottom. After 3 years (to permit the key to settle), the bottom that the funnel to be removed and the funnel put in a bell jar with a beaker below it. The pitch slowly flows the end of the funnel, forming a big drop. About every te a drop drops off into the beaker.

While every drop takes a te to form, it only takes around a tenth that a second to fall. In the 89 year the experiment has been running, nine drops have fallen for this reason far. Nobody has yet it was observed a drop falling. Since the 1990s the experiment has been repetitively monitored by a net camera, but when the eighth drop dropped 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 beneath the funnel, which had actually been filled sufficiently by ahead drops to interfere through the experiment. Over there is a net site dedicated to watching for the tenth drop to fall.

native the price of flow over the duration of the experiment, it has actually been approximated that the key in the funnel has a viscosity 230 billion times better than water. The is estimated that enough pitch remains in the funnel because that the experiment to proceed for another century.

right here is a time-lapse video of the descent of the 9th drop and the creating of the tenth drop extending the duration from April 2012 with April 2015.

This chemistry Heritage structure video includes a summary of the experiment by its lengthy term custodian, the so late Prof. Man Mainstone.

A pitch drop experiment was begun at Trinity college in Dublin, Ireland in 1944. The experiment laid forget on a shelf for decades as numerous drops formed and also fell. In April that 2013, as one more drop to be forming, a web camera was set up to continuously monitor the experiment, and on July 11, 2013 the drop was observed come fall, the first time such an event had been recorded. Below is a news report from RTE around the experiment reflecting the fall falling.

right here is the complete time-lapse the the Dublin autumn falling.

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If you"ve got to that phase of life where the heart-pounding excited of watching repaint dry is too lot to take, it"s simple to collection up your own pitch fall experiment. Every you need is a glass funnel and some pitch (you have the right to buy high-grade optical key from GotGrit.com). I"d put a rubber stopper in the bottom that the funnel to originally seal it. Heat the pitch gently ~ above a oven until the pours easily (use a disposable pan, because you"ll never have the ability to remove all the pitch), then to water it into the funnel. Wait a couple of weeks until the pitch has entirely cooled, then remove the stopper, set the funnel top top a stand v something to record the ultimate drops, and also away friend go. Pitch come in various grades ranked through “hardness” (actually, viscosity), and also it"s better to pick one the the softer (lower numbered) grades. A key drop experiment was reportedly started Aberystwyth university in Wales in 1914, but to date has yet to produce a single drop.