120 INTRODUCTION TO GENERAL SCIENCE 



6. State your conclusions in regard to nitrogen as a chemi- 

 cal element. 



The nitrogen, as prepared in this experiment, is pure; that 

 obtained from the air, in Experiment 40, was very impure. 



88. EFFECTS OF PAINTING WOOD PRESERVATION 



Painting is looked upon more as a matter of decoration 

 than as a protection from the effects of the weather. Really, 

 however, beauty is a secondary consideration, although it 

 should not be neglected. Pleasing combinations of tints and 

 shades are capable of producing results which may go far 

 toward making an otherwise ugly place appear attractive. 



Whenever anything is exposed to the oxygen of the air, 

 decay begins. Moisture aids this disintegration, as do also 

 heat and cold. Paint excludes both the air and moisture, 

 and prevents to a great extent the harmful effects of low 

 temperature. All woodwork and metal work should be pro- 

 tected from the weather, and the protecting material should 

 be carefully chosen. 



There is nothing equal to linseed oil as a protective agent. 

 In the oil there should be blended red lead, white lead, and, for 

 some purposes, zinc white. Other oils and other materials 

 do not produce equally lasting protection and should be re^ 

 jected where protection is really desired. The color of the 

 paints is a small matter, and all paints, except red, are made 

 from white paint. It is often better to buy the white paint 

 and color it to suit, as it is easier to detect foreign materials in 

 white paint. 



Wood can also be preserved by creosote or by zinc chloride. 

 Graphite, applied to stoves, protects them like paint from 

 atmospheric oxygen. 



