Lesson XII. j 



CHEMISTRY. 



become extinguished because it has ex- 

 hausted all the oxygen in the jar. 



T. Why did the water rise in the 

 jar, and what became of the white fumes ? 

 P. The water rose in the jar because 

 the air in the jar having lost about one- 

 fifth of its volume, and the water occupies 

 its place. The white fumes were dissolved 

 by the water, and pure nitrogen remains. 



TV What has become of the one- 

 fifth of the air in the jar? 



P. It is exhausted by the phosphorus 

 in the process of combustion, being the 

 i of the air, for you know that 100 

 volumes of atmospheric air contains 



. olumes of nitrogen 

 21 oxygen 



Ja ^5 carbonic acid 



and the vapour of water. 



T. As this method of preparing 

 nitrogen is not altogether free from certain 

 objections, prepare the gas by some other 

 method. 



/'.[Experiment 23.] Here is a porce- 

 lain tube filled with the turnings of copper, 

 now when this tube is heated to redness 

 and a stream of atmospheric air passed 

 through the tube, the nitrogen will issue 

 at the opposite end. [Does so.] You ob- 

 serve that the copper turnings, which have 

 cooled, weigh more than they did 1 

 put them into the tube ; they have com- 

 bined with the oxygen of the air, to form 



"f copper. 



130. T. Is there not another method 

 )f preparing the gasf 



P. Yes, by passing chlorine gas through 

 a strong solution of ammonia; but 

 preparation is attended with danger to 

 inexperienced persons, I will not try it. 



131. T. Give me some illustrations of 

 the properties of this gas. 



P. [Experiment 24.] Here is a small 

 jar full of it ; observe what takes place 

 when I introduce a lighted taper. [Does 

 so, and the taper is extinguished.] The 

 reason the candle went out, is because 

 nitrogen cannot support combustion, [Ex- 

 periment 25]. This jar also contains 

 nitrogen, and as I am going to add some 

 lime-water to it, observe what takes place. 

 [Does so, and no change is observed ] You 

 seem surprised that there was not any 

 change, but I never expected to see any ; 

 and only used these means to satisfy 

 myself that the jar contained nitrogen and 

 not carbonic acid, a gas that changes lime- 

 water white by forming an insoluble salt 

 called carbonate of lime. 



GENERAL QUESTIONS ON LESS 



1. What is nitrogen ? ' 



2. Give the derivation of its name and 

 meaning. 



nitrogen known by any other name ? 

 1. How is this gas obtained, and is there 

 any danger attending its preparation ? 



5. Give the composition of atmospheric 

 air. 



6. Illustrate the properties of this gas by 

 experiments. 



LESSON XII. 



have now to examine the halogens, or tail j.roilurcrt : Chlorine, discovered by 

 Scheele, in Sweden, in 177J; Iodine, discovered by Courtois, in France, in 1811 ; Hrornine, 

 discovered by Balard, in France, in 1826 ; and Fluorine, first accurately examined by 

 Scheele, in Swu 



QUESTIONS. 



132. r. What is Chlorine ? 



/'. A greenish-yellow, pungent gan, 



'.) rrttinhliug ! . oe, and 



uurine. Its specific gravity : 



thcnamed 



/'. Hy placing some finely powdered 

 black oxide of manganese in a Mil 

 pouring some strong liquid hydrochloric 



heat, 



mixing equal parts of the black 02 



. x i 11* / x fiiiAitiiti.iiutiii'aiiniMiiivuiav* 1 



lcA/<,ro,( X Apof),grcc. , / ^ ^h,, ftud 



' to lts colour ' sulphuric acid (equal part, of water 



1-U. r. How is it prepared t < and acid) to them when placed in the flask. 



