LESSONS IN CHEMISTRY. 113 



hydrogen in its composition. Pure water has been decomposed 

 by the action of several different metals and by the electric 

 spark. It has been analyzed and found to contain only the gases 

 oxygen and hydrogen. 



Pure water at ordinary temperature is a clear transparent 

 liquid, tasteless, odorless and neutral in its reactions. It is es- 

 sential to the life of plants and animals, forming the chief in- 

 gredient of all the liquids they contain. It is the standard for 

 obtaining the specific gravity of solids and liquids. It is the 

 standard for the measurement of specific heat. It is an abundant 

 ingredient of many rocks. Its presence or absence determines 

 whether a region shall be a barren waste or a teeming garden. As 

 a chemical compound, the combining tendencies of water extend 

 over a wider range than those of any other compound. Its com- 

 binations with other substances are usually called hydrates. 

 Water combines with the elements bromine and chlorine, forming 

 an exception to the general rule that combinations do not take 

 place between elementary and compound bodies. Water dis- 

 solves more substances than any other liquid known, so that in 

 nature pure water is seldom or never seen. But it may be easily 

 purified by filtration and distillation. 



The purest water in nature is rain water, which falls after it has 

 rained for some time. During the first part of the storm the rain 

 washes dust and impurities out of the air, so that later the water 

 is nearly pure. Large quantities of natural waters contain car- 

 bonate of lime in solution, and are called hard waters, forming 

 deposits on the inside of boilers and kettles. Others contain iron, 

 salt, soda and other minerals, some of which are of medicinal value. 

 The solvent power of water is of great value in chemical operations, 

 as well as in the operations of nature. In some cases substances 

 which do not act upon one another when dry act promptly when 

 in solution, the particles come into more intimate contact and 

 chemical action seems to be facilitated. In solutions the particles 

 of the dissolving liquid seems to have some attraction for the 

 particles of the dissolved substances so that they are uniformly 

 distributed through the solution, but this attracting power may 



L.S. 8 



