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J. Perelman
"Entertaining physics". Book 1.
Chapter 5. Properties of liquids and gases

NATURAL FORM OF LIQUID

We used to think that liquids have no own form. This is not true. Natural form of any fluid - ball. Usually the force of gravity prevents liquid to take this form, and the liquid or spreads a thin layer, if spilled without a vessel, or takes the form of a vessel, if poured into it. Being inside another liquid of the same specific gravity, liquid according to the law of Archimedes “loses” her weight: she weighs nothing, the weight of it is not valid when the fluid takes its natural spherical shape.

Olive oil* floats in water but sinks in alcohol. It is therefore possible to prepare a mixture of water and alcohol, in which the oil does not sink and nothing POPs up. Introducing into the mixture a little oil through a syringe, we will see a strange thing: the oil is collected in the large round drop, which is not uplyvaet and does not sink, and hanging motionless [To form the ball did not seem distorted, it is necessary to produce experience in a vessel with a flat wall or in a vessel of any shape, but is placed inside the water-filled vessel with flat walls)].


The oil inside the vessel with diluted alcohol is going to a ball, which does not sink and nothing POPs up (the experience of the Plateau).
This, however, is not all. Passing through the center of the liquid oil of the ball a long wooden rod or wire, rotate them. Oil ball takes part in the rotation. (Experience can do, if spread on the axis of a small moistened with oil cardboard circle, which all would have remained inside the bowl.) Under the influence of rotation of the ball starts first be flattened, and then after a few seconds separates themselves from the ring. Torn to pieces, this ring does not form a shapeless pieces, and new spherical droplets that continue to circle around the Central Orb.

If oil ball in alcohol quickly rotate through stuck his rod is separated from the ball ring.

For the first time this learning experience has made Belgian physicist Plateau. Here we describe the experience of the Plateau in its classical form. Much easier and no less instructive to produce it in a different form. Small glass rinse with water, fill with olive oil and put on the bottom of a large glass; the latter is poured cautiously so much alcohol that the small glass was all into it shipped. Then the great wall Cup of the spoon to carefully add a little water. The surface of the oil in a small glass becomes convex; convexity gradually increases, and when a sufficient number of uploaded water rises out of the glass, forming a ball rather large, hanging inside a mixture of alcohol and water.


Simplifying the experience of the Plateau.

In the absence of alcohol, you can do this experience with aniline - liquid, which at ordinary temperatures is heavier than water, and at 75 - 85°C easier. Heating the water, we can, therefore, make aniline to swim inside it, and it takes the form of a large spherical drops. At room temperature a drop of aniline is balanced in the salt solution [other liquids convenient orthotoluidine - dark red liquid; at 24° it has the same density as water and salt water, in which are immersed orthotoluidine].

*Olive oil - formerly known as olive oil.

Entertaining physics J. Perelman

 




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