SCIENTIFIC AND PRACTICAL AGRICULTURE. 237 



What do the figures after the symbols show? The atomie 

 weight. See 36 and 37. 



What is the atomic weight of hydrogen ? 37. Of carbon ? 37. 

 Of oxygen? 37. Of magn^^sium ? 37. ^ Of sulphur? 37. What is 

 the lightest of all bodies ? 37 and 22. 



What two elements combine to form chloric acid? (See Table 

 I.) What is the symbol for oxygen ? What for chlorine ? What 

 will be the symbol for chloric acid, if 5 atoms of oxygen combine 

 with 1 of chlorine to form it? 



What two elements combine to form sulphuric acid ? (See Ta- 

 ble I.) How many atoms of oxygen to one of sulphur? What 

 then shall be the symbol for sulphuric acid? The, atomic weight 

 of oxygen being 8, and that of sulphur being 16; and 3 atoms of 

 oxygen combining with 1 of sulphur to form sulphuric acid, what 

 will be the atomic weight of sulphuric acid? Ans. 16-|-3x8=40. 



How are the compounds of oxygen with each element below it 

 in Table I. placed? 37. How are the compounds of all the ele- 

 ments below oxygen with each other placed '? 37. ^ 



What is chloride of sodium composed of? Sulphuret of iron? 

 Sulphuret of hydrogen ? Light carburet of hydrogen ? Heavy 

 carburet of hydrogen? Ammonia? In ammonia, how many 

 atoms of hydrogen to 1 of nitrogen? Why is NH^ the symbol 

 for ammonia? Why is' 17 the atomic weight of ammonia? 



(These symbols show what each compound is made up of They 

 are not designed to be committed, but to be used for reference. 

 The reader, for instance, might wish to ascertain what carbonic 

 acid is. If he turn to this table, he will see carbonic acid, CO^ 22. 

 The C shows one atom of carbon, 6 ; the 0", two atoms of oxy- 

 gen 8-|-8 = 16; and so of all the other compounds, and of the 

 salts in Table II. formed from these compounds.) 



How many compounds in Table I. are called acids ? 39. How 

 many are called oxides ? 39. Why are the oxides called also 

 bases? 39. Why are- the salts formed from these acids and bases 

 called oxygen salts ? 40. How does the name of these salts 

 always end ? 40. Are there other salts ? 40. If carbonic acid 

 were combined with soda, what would be the name of the salt 

 thus formed ? 40. If the soda should take a double portion of 

 the acid, what prefix would precede its name ? 40. What other 

 prefix signifies the same as bi? 40. 



Can you distinguish between those compounds whose name 

 ends in uret, and the salts whose names end in ate ? 41. 



What is a protoxide ? 42. A sesquioxide ? 42. A perox- 

 ide? 42. 



Wil), you tell me what is the composition of sulphate of iron 

 (copperas)? 43 and Table II. Of sulphate of soda (Glauber's 

 salt)? 43 and Table II. When water exists in crystals, what is 

 it called ? 43. 



What is the -imposition of sulphate of lime (plaster, gypsum)? 



