WATER 219 



and oxygen are exploded and the water formed is weighed or the amount 

 of each gas used is measured. Also water is decomposed by electrolysis 

 and the hydrogen and oxygen thus formed (the only things formed) 

 are measured. 



The heat given off in the combination of the gases is enormous, 

 indeed, it is the most exothermic of all chemical reactions, 67,500 

 calories or heat units being evolved in the combination of 16 grams of 

 oxygen with 2.016 grams of hydrogen — a calorie is that amount of heat 

 which will raise one gram of water 1 degree centigrade. In the absence 

 of indifferent gases, or an excess of one of the reacting gases, the reac- 

 tion is not only so violent as to raise the gases to the combination tem- 

 perature, 2,000° C, but to carry them beyond to 2,844° C, at which 

 temperature only about one third of the gases combine, the remainder 

 doing so gradually as the temperature falls. Almost any non-reactive 

 (catalytic), highly heated substance, such as platinum sponge, or wire, 

 stone, porcelain, glass, etc., will bring about a combination. 



An oxy-hydrogen blowpipe is an arrangement for utilizing this 

 heat energy, by bringing the two gases together in such a way that they 

 will produce a sharp, intensely hot flame. The apparatus is so fashioned 

 that the gases are conducted separately through the exit where they 

 are to be lighted, thus avoiding any possibility of explosion, which 

 otherwise takes place, if they are mixed. By means of such a flame, a 

 temperature of 2,000° C. can be obtained. 



Having learned that water (at least in the form of its components) 

 is older than even the earth itself, that its constituent parts existed 

 practically at the beginning of things, and also that it is not an element, 

 but built up of two gases combined in a definite proportion, let us now 

 take up the substance itself and study it in its various forms. These are 

 quite numerous, but may all be classified under three fundamental 

 heads: gaseous, liquid, and solid water. 



The fact that it can exist in these three states is not so remarkable, 

 since it is possible to transform every known substance, elementary or 

 combined (provided the latter do not decompose) into these three 

 states of aggregation ; but that the three should all be within the range 

 of ordinary temperatures is rather extraordinary. There are only a 

 few common substances of which this is true, e. g., ammonia, benzene, 

 etc. It will be seen, moreover, that water has a good many other note- 

 worthy properties. As compared with other substances it is nearly 

 always exceptional, and stands at the extremes. 



Gaseous Water. — Steam and atmospheric water vapor belong in this 

 category. It is not until we go to some of the arid desert regions of our 

 earth that we realize the importance of the latter. Where there is no 

 moisture in the atmosphere, there can be no clouds formed, and hence 

 there can be no rain, which means, of course, that such a place must be 



