COMPOUNDS 203 



the ocean water contains nearly 3^ of mineral salts in 

 solution. A large part of this dissolved matter is com- 

 mon salt (NaCl) ; the limestone (CaCO 3 ) in 

 ocean water furnishes material for the shells 

 of many small sea animals. 



In chemistry H 2 O is of great value. It 

 dissolves more different things than any other 

 liquid, and as it is a neutral compound (not 

 acting chemically upon the substance dis- 

 solved in it), water is a very useful solvent. To 

 plant life H 2 O is of first importance. Plants 

 absorb large quantities of water through their 

 roots ; in their leaves and bark some of it is FlG - 134 

 combined with carbon, making the great bulk of the 

 solid matter. Water is hardly less important in animal 

 life. It is present in nearly all foods, and all parts of 

 the animal body contain a great deal of it. 



Experiment 128. Arrange apparatus for making H, as in 

 Experiment 121. Heat the glass tube and draw it out to a small 

 opening (Fig. 134). Into the test tube put Zn and HC1 

 to make H. When the gas has flowed a few seconds, col- 

 lect some in a small 

 test tube (by hold- 

 ing the tube mouth 

 downward over the 

 end of the glass de- 

 livery tube); touch a 



lighted match to the 



FIG. 135 , . ... 



gas collected in this 



small test tube. If 



a slight explosion occurs, wait a moment and then repeat ; if the 

 gas only burns quietly, then light the gas escaping from the 

 delivery tube. This gas is H, now burning in air (containing O). 



