l-'t 



CHEMISTRY. 



[Lesson XI. 



have placed the end of the bent glass tube 

 (Fig. 32, a,) under water, and that bubbles 

 of hydrogen arc escaping. I will apply a 

 lighted taper to them, and we shall see 

 that they will ignite and explode at the 

 same time. [Applies the taper, and the 

 bubbles explode]. Here is another ex- 

 periment to prove it is inflammable. [Ex- 

 .periment 20]. You see that this bottle has 

 some zinc cuttings and diluted sulphuric 

 acid in it, and that instead of a glass tube, 

 the cork (which fits tight) has a piece of 

 tobacco-pipe adapted to it. I will allow 

 some more of the gas to escape, so as to 

 displace the air before I apply a light, and 

 then you will see that it burns. [When the 

 light is applied, the gas burns with a very 

 faint light] 



124. T. .What other peculiarities are 

 there about hydrogen ? 



P. [Experiment 21]. You observe that 

 the hydrogen is still burning, [Uses the 

 bottle with the tobacco-pipe, Experiment 

 20], and that the sides of the tumbler I 

 now hold over it are covered with dew. 

 This dew is water formed by the combus- 



tion of hydrogen, which unites with the 

 oxygen of the air. 



125. T. As hydrogen burns without 

 supporting combustion, and oxygen sup- 

 ports combustionwithout burning, it is prob- 

 able that when combined a very rapid com- 

 bustion will be the result. Is this the case? 



P. It is, and advantage has been taken 

 of the fact, to produce the most violent 

 degree of heat known, by means of an 

 apparatus called the oxy- hydrogen blow- 

 pipe. In addition to this the oxy-hydrogen 

 gas is thrown upon lime to produce ;i very 

 brilliant light 



GENERAL QUESTIONS ON LESSON X. 



1. What is there peculiar about the pre- 

 paration of hydrogen gas ? 



2. W r hy is this gas named hydrogen ? 



3. Explain the difference between pon- 

 derable and imponderable bodies. 



4. Give the various methods adopted to 

 procure hydrogen. 



5. Does hydrogen support combustion ? 



6. Give some illustrations of the pro- 

 perties of this gas. 



LESSON XI. 



THE next elementary substance we have to investigate is called Nitrogen, a gas that 

 constitutes about four-fifths of the atmosphere, and is largely diffused in nature, 

 especially in the organic kingdom. It was discovered in Scotland, in 1774, by 

 Dr. D. Rutherford. Nitrogen means the generator of nitre, deriving its name from two 

 Greek words, nitron, (vnpOv), nitre ; and geimaein, (yevvativ} to produce ; it is also, 

 erroneously, called azote, from a (a) privative, and zoe (frr;), life ; meaning the life- 

 destroyer, because an animal cannot breathe it without dying, whereas if they breathe 

 oxygen it is so stimulating that they will go mad. Its specific gravity is 0'972, and the 

 gas is devoid of taste, smell, and colour. 



QUESTIONS. 



matic trough ; then touch the phosphorus* 

 with a piece of hot wire, and cover the jar 

 over it. [Does so]. You observe, the jar is 



126. T. How is 

 Nitrogen obtained? 

 P. By burning 

 phosphorus in air 

 enclosed in a jar 

 orer water, as in 

 Fig. 34. [Experi- 

 ment 22]. Take 

 a piece of phos- 

 phorus about the 

 jsize of a large pea, 

 Iplace it in a small 

 ^earthenware dish, 

 and let it lloat on the surface of the pneu- 



being filled with dense white fumes, produced 

 by the combination of phosphorus with 

 oxygen, to form phosphoric acid. The 

 fumes have now disappeared, and you see 

 that the water has risen about one-fifth of the 

 height in the jar, and the phosphorus has 



* Phosphorus is a dangerous thing to handle, as 

 the warmth of the hand may cause it to ignite. 

 When cut, it should be done under water, and 

 always preserved in a bottle of water. 



