34 LESSONS IN CHEMISTRY. 



CHAPTER 11. 



MATERIALS EXISTING IN WATER. 



30. We have passed in review the substances which enter 

 into the composition of the atmosphere, and which therefore 

 are accessible to the growing plant: we will now consider 

 what Water is capable of supplying for its nourishment. 



Composition of Water. — This substance, which is met with 

 in nature under three forms — in a hard solid form, as ice ; in 

 a fluid state ; and in a gaseous form, as vapour or steam — 

 was, like the air, imagined by the ancient philosophers to be 

 a simple element. It seems difficult to be believed by those 

 unacquainted with the wonderful things which chemistry is 

 capable of demonstrating by experiment, that the pure, 

 healthful, and refreshing liquid, which in every country in the 

 world is such a necessary of existence, should be composed of 

 an unwholesome gas, one of the most inflammable bodies in 

 nature, united with that remarkable life-and-flame-supporthig 

 element, oxygen, which we described as being so important an 

 ingredient of the air that we breathe. 



31. If we cause water to boil, we produce steam, the bulk 

 of which is 1,694 times greater than the water from which it 

 is formed. If we pass the steam through an iron tube, such as 

 a gun barrel, placed across a small furnace and kept at a red 

 heat, we find that a peculiar gas issues from the tube, which 

 we can collect over water, while at the same time its inner 

 surface acquhes a coating of rust. This gas is named 

 Hydrogen, and is the inflammable element which, united 

 with oxygen, forms water. In the experiment, the steam, in 

 passing over the red-hot metal, is decomposed; one of its 

 ingi-edients, as we have stated, issues from the pipe as a gas, 

 while its other element, oxygen, unites with the metal, pro- 

 ducing the covering of rust, which is what is termed an 

 oxide, being a compound of oxygen and iron. Hydrogen gas 

 forms one pound in every nine pounds of water, so that for 



