Man's physical universe

xanabras

supersaturated solutions.

REGULARITIES OF SOLUTIONS 243

while cooling to insure crystallization.

Fudge is crystalline, and it is stirred rapidly

Stirring is frequently all that is

necessary to cause the excess solute in a supersaturated solution to

separate out.

Jellies are supersaturated solutions, and sometimes the excess sugar

crystallizes out in beautiful large cubes called "rock candy." Rock

candy can also be made by hanging a string in a supersaturated solution

of sugar in water, the excess sugar crystallizing on the string.

Gases and Liquids Show Great Variations in Solubility.

Gases are completely miscible with other gases. This means that

they are mutually soluble in each other in all proportions. Thus the

atmosphere is a mixture of the gases, nitrogen, oxygen, carbon dioxide,

water vapor, and a few rare gases that are completely miscible in each

other. Some liquid pairs, such as alcohol and water, or kerosene and

gasoline, are completely miscible with each other, but many liquids

are only partially so; gasoline and water are slightly miscible in each

other.

A concentrated solution is one that contains a relatively large amount

of solute in a given amount of solvent, whereas a dilute solution contains

a relatively small amount of solute in a given amount of solvent.

The Amount of Gas Which Will Dissolve in a Liquid Depends upon the

Temperature and Pressure.

The individual (specific) properties of different gases make their

solubilities in a given liquid solvent different.

Relative Solubilities of Common Gases in Water.

Hydrogen, nitrogen,

and oxygen are slightly soluble, 2-4 volumes to 100 volumes of

water.

Carbon dioxide and chlorine are fairly soluble, several hundred

volumes to 100 volumes of water.

Sulfur dioxide, ammonia, hydrogen chloride are very soluble, several

thousand volumes to 100 volumes of water.

In the case of very soluble gases, there is probably a chemical union

of the solute particles with the water rholecules^.

Slightly or fairly soluble gases follow the gas laws when they are dissolved

in liquid solvents; it has been observed that an increase in

pressure will increase the

weight of gas dissolved in a given volume oj

liquid. This is a statement of Henry s Law.

The increased solubility of carbon dioxide in water with increased

pressure is used in preparing carbonated drinks. When the cap of a

soda-water bottle is removed, the liquid effervesces because the pres-

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