338 



ON THE PLACE OF FISH IN 



Complete 

 oxidation of 

 Carbon 

 always gives 

 rise to Car- 

 bonic acid. 



Hydrogen. 



Nitrogen. 



he watches them in a beam of sunlight curling slowly 

 upwards from his pipe, and, rolling gently into lazy 

 folds, linger over him with an air of tranquillity and 

 rest. 



Larger particles of it are the terror of the laundry- 

 maid as she sees them settling on the linen she has 

 carefully washed to such dainty whiteness. 



Carbon, too, makes the fortune of the chimney-sweep 

 (whose occupation the Smoke Abatement Committee 

 are trying to abolish), and his sack is valued by many. 



Under the name " black lead," which contains no 

 lead at all, it is used for drawing-pencils, and it is met 

 with in its purest form in the diamond. 



Mixed with small quantities of other things Car- 

 bon forms the bulk of coal, charcoal and wood. 

 Fine heated particles of it are the source of light of 

 ordinary flames. 



The union of Carbon with Oxygen forms invisible 

 gases, and THE COMPLETE OXIDATION OF CARBON 

 ALWAYS PRODUCES CARBONIC ACID, an invisible gas 

 of which more will be presently said. 



HYDROGEN is a gas which occurs naturally in com- 

 bination with some other element, and when it is 

 wanted for use (as for the oxy-hydrogen light) or for 

 the purpose of examining it, some compound con- 

 taining it is " split up " so that the hydrogen is set 

 free. The compound usually chosen for this purpose 

 is Hydrogen-Oxide, commonly called water (see 



P- 339). 



NITROGEN, like Oxygen, occurs free (that is, not 

 as a compound) in the air. It also forms many com- 

 pounds, of which two familiar ones are nitrous oxide 

 (laughing gas) and nitre (saltpetre.) 



