CHAPTER VI 

 LIQUIDS AND THEIR PROPERTIES 



86. Properties of Liquids. The special characteristics 

 of liquids are: 



Mobility, or freedom to change form, as liquids do when 

 poured from a pitcher into a cup. 



Incompressibility, or resistance to pressure which tends to 

 reduce the bulk. A bottle, when full of water, may be 

 burst by putting in a cork. 



Viscosity, or tendency of the particles to cling together. 

 The form of a drop is due to viscosity. 



Volatility, or tendency to change to a vapor. Ether on 

 the 'skin disappears very quickly. 



Water, the most familiar liquid, is used as a standard 

 in comparison of liquids. Alcohol is less dense and more 

 volatile than water; tar is a very viscous liquid; molasses, 

 while less viscous than tar, is more so than water. All 

 liquids are practically incompressible. 



87. Hydraulic Presses and Elevators. We make use 

 of the incompressibility and mobility of liquids in running 

 certain machines, like presses and elevators. In both 

 presses and elevators, a platform is placed upon a piston 

 or plunger in a water-tight cylinder. Water is forced into 

 the cylinder, and as the water pushes up the plunger, the 

 platform rises. In the press, the object to be compressed is 

 placed upon the platform, which moves up until it meets 

 an immovable surface. Great pressure is then exerted 

 against the substance on the platform. Bundles of cotton, 

 hay, or paper are thus made into compact bales. 



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