EXPERIMENTS IN CHEMISTRY AND PHYSICS 19 



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to show where the water stood, you may measure the space occupied by 

 the water in the jar. This space will be found to be almost exactly one fifth 

 of the cubic contents of the jar. It was 

 occupied by the oxygen of the air, this hav- 

 ing been used up by the oxidation of the 

 phosphorus. The remaining space at the 

 completion of the experiment is occupied by 

 the nitrogen, which makes the remaining 

 four fifths of the atmosphere. 



The physical properties of nitrogen 

 are its lack of color, taste, and odor. 

 Its chief chemical characteristics are 



its inability to support combustion and ^^| .^^ ^^.- . :-v ^^ ) 

 its slight affinity for other substances. " 



Experiment to show the amount 

 of nitrogen present in the air. 



Mineral Matter in Living Things. — 

 We saw in the experiment for the detection 

 of carbon by burning, that the sand or gravel contained no carbon. If a piece 

 of wood is burned in a very hot fire, the carbon in it will all be consumed, 

 and eventually nothing will be left except a grayish ash. This ash is well 

 seen after a wood fire in the fireplace, or after a bonfire of dry leaves. 

 This ash consists entirely of mineral matter which the plant has taken up 

 from the soil, dissolved in water, and which has been stored in the wood 

 or leaves. 



If we were able by careful analysis to reduce a plant and an animal 

 to the chemical compounds of which they were formed, we should discover 

 that both contained mineral or inorganic material. We have just seen 

 examples of this in plants. Mineral matter is found in bone, in the shells 

 covering mollusks, and in many of the other parts of the bodies of animals. 



Water in Living Things. — Water forms an important part of the sub- 

 stance of plants and animals. This can easily be proved by weighing a 

 number of green leaves, placing them in a hot oven for a few moments, and 

 then reweighing. How much weight of a given quantity of leaves is made 

 up of water? Make the same experiment with some soft-bodied ani- 

 mal, as an oyster removed from the shell. Some jellyfish are composed 

 of over 90 per cent water. The human body contains 60 per cent 

 water. 



Gases Present. — Some gases are found in a free state in the bodies of 

 plants or animals. Oxygen is of course present wherever oxidation is 

 taking place, as is carbon dioxide. Other gases may be present in minute 

 quantities. 



Classification of Organic Matter. — The organic or living part 

 of a plant or animal is made up largely of the elements carbon, 

 hydrogen, oxygen, and nitrogen, with a very minute amount of 



