170 METALLOIDS. 



Howisnitro- ^- PREPARATION. Nitrogen is pre- 

 gen prepared? p are d from ordinary air by removing its 

 oxygen. For this purpose a small portion of phospho- 

 rus is floated on a slice of cork upon water, and then 

 kindled, and a vial inverted over it. 

 As it burns, it abstracts the oxygen ; 

 the water rises to take its place, and 

 what is left of the air is nitrogen. 

 The cork should be a little hol- 

 lowed out, and chalk scraped into 

 the cavity. Water must be poured into the saucer as 

 the first portion rises into the bottle. The bottle is 

 then cooled, either by water or long standing, and 

 co-rked while yet inverted It is then shaken, to wash 

 the gas. A piece of phosphorus, of the size of a large 

 pea, is sufficient for the preparation of half a pint of 

 gas. 



Explain the 413. EXPLANATION. The burning phos- 



process. phorus selects all of the oxygen atoms in 



the air, and, by combining with them, converts them 

 into solid particles of a certain oxide of phosphorus, 

 called phosphoric acid. These particles at first ap- 

 pear as a white smoke, and are afterward dissolved in 

 the water. 



414. NITROGEN EXTINGUISHES FLAME. If 



Does nitrogen 



extinguish a burning taper be lowered into the bottle of 

 flame? y. n j trO g enj as above prepared, it will be im- 

 mediately extinguished. Flame is the brightness which 

 accompanies active chemical combination, but here is 

 nothing to combine. Nitrogen is a sloth among the 

 elements, possessing no degree of chemical activity. 



