274 FIRST YEAR SCIENCE 



was used in Experiment 35. Mark the depth to which it sinks. 

 Place the hydrometer now in sea water and mark the depth to which 

 it sinks. If sea water cannot be obtained, dissolve in a pint of fresh 

 water about 15 g., or half an ounce, of salt. This will give the water 

 about the same amount of dissolved solid material as sea water would 

 have. About how much more of its length does the hydrometer sink 

 in fresh water than in sea water ? Will a piece of ice project more 

 out of salt water than it would out of fresh water ? 



Experiment 123. If ocean water can be obtained, boil down about 

 a pint of it in an open dish. Taste of the residue which is left. 

 What is the principal constituent of this residue ? 



There is probably no water on the surface of the earth 

 which is absolutely pure. Water is the greatest solvent 

 known, and it dissolves-to a greater or less extent almost 

 all substances with which it comes in contact. When the 

 rivers run into the sea, they carry with them whatever 

 their water has dissolved from the land, and when the sun 

 evaporates the water, and it is borne away again to fall 

 upon the land, the dissolved material is left behind in the 

 ocean. 



Thus the sea has for all time been receiving the soluble 

 contributions from the land. It is easy to prove that it 

 contains salt, for we can taste it. It must contain lime, 

 for corals and shell animals depend upon this for the 

 hard parts of their bodies. There must be organic food 

 material in it, or else fixed animals like oysters could not 

 get food. It contains air, for without air fishes could not 

 breathe. These are the principal substances which we 

 need to consider in the study of the ocean water, but the 

 chemist can find many other substances dissolved in it. 

 On account of the materials dissolved, sea water weighs 

 more than fresh water, or has a greater specific gravity. 

 A cubic foot of fresh water weighs about 62.5 Ibs. whereas 

 a cubic foot of sea water weighs over 64.25 Ibs. 



