77V POPULAR CHEMISTRY. 



7o 



given weight, 222| pounds, to grains, we multiply by 7,000, the 



14,000,000 

 number of grains in a pound, making : ^ grains. 



Then 



14,000,000 1,440 



9 



: x in cubic feet. 



9 ' ' 1,728 

 x 41,817 cubic feet. 



This would be enough to fill a spherical balloon 43 feet in 

 diameter. 



84 1. IVliy will pine-wood ignite more easily than 

 maple ? 



It is richer in hydrocarbons, that are readily volatile. 



2. Wliy is fire-damp more dangerous tlian cholte- 

 damp ? 



Fire-damp, CH 4 , contains no O. At the appropriate tem- 

 perature of kindling, when mixed with air, it is a dangerous 

 explosive. Choke-damp, CO 2 , is already a stable compound con- 

 taining the largest proportion of O that can unite with C. It 

 is, therefore, not explosive. 



3. Hepresent the reaction in malting CO 2 , shoiving the 

 atomic weights, as in the preparation of O on page 12. 



(40+12 + 48) + 2 (1 + 35. 5) = (40 + 71) + (2 + 16) + (12 + 32). 

 100 + 73 = 111 + 18 + 44. 

 173 = 173. 



4. Should one taJce a light into a room where the gas is 

 escaping ? 



No. An important constituent of illuminating gas is the 

 dreaded fire-damp, CH 4 . Mixed with the air in the room, it 

 may be exploded by introducing a lighted match or candle. 



5. irtiy does it dull a Jcnife to sharpen a pencil ? 



The particles of graphite in the pencil are very hard, and 

 the knife edge is worn away by friction. 



6. Where was the C, now contained in the coal, before 

 the Carboniferous age ? 



Probably most of it was combined with O, forming CO 3 in 

 a densely charged atmosphere. 



