CHAPTER XVI 



WATER AND THE ELEMENTS COMPOSING IT 



Water. We must next turn our attention to ivater and en- 

 deavour, as we did in the case of air, to investigate its chemical 

 composition, &c. Let us briefly review what we already know 

 of it. 



It is a clear liquid with a blue-green colour, which is best seen 

 by causing light to pass through a considerable length of water. 

 It boils at 100 3 C., and is then converted into steam. It freezes at 

 C., becoming ice. Its density, i.e., mass of 1 c.c. , is Iat4 C. 

 and slightly less at any other temperature, owing to the fact 

 that water expands when either cooled below or heated above 4 C. 

 It has the power of dissolving many substances, e.g., salt, sugar, 

 etc., forming solutions from which the water may be evaporated 

 away, leaving the solid behind. But these facts tell us nothing of 

 the chemical nature of water because we have no changes in com- 

 position. The water, present all the time, is not converted into 

 any new product. We must therefore try to get a new product 

 from the water. We will first try the action of metals, and as in 

 the case of our studies upon air, we will use iron first. If iron be 

 left in water it is found to form a considerable quantity of riist ; 

 but this may be due to the air which we now know may be 

 dissolved in water ; and if the iron be placed in water in a tube, 

 this water, having been first well boiled to drive off the air, and 

 the tube then sealed in a blow-pipe, the iron either does not rust, 

 or does so to only a very slight extent. There is, therefore, no 

 conclusion derivable from this experiment. Perhaps, however, 

 if the iron were heated it might act on the water. 



EXPT. 234. Place some iron filings in the tube CA, and 

 let the end A dip under water. To the end C fit a delivery 



