Ximeetone. l* 



very hard, giving off a metallic musical tone 

 when struck by any hard substance. 



We have already stated that limestone is a 

 compound of ordinary lime and carbon diox- 

 ide, forming a carbonate of lime. This state- 

 ment does not give a complete analysis of all 

 the elements entering into limestone. In the 

 first place lime itself is a compound formed 

 of two elementary substances, calcium and 

 oxygen. The lime molecule is composed of 

 one atom of calcium and one of oxygen. 

 Neither calcium nor lime is found pure in 

 nature. Inasmuch as carbon dioxide is com- 

 posed of one atom of carbon and two of 

 oxygen, and lime is composed of one atom of 

 calcium and one of oxygen, when we have the 

 two combined the molecule of carbonate of 

 lime, or, as it is technically called, calcic car- 

 bonate, is composed of one atom of calcium, 

 one of carbon and three of oxygen, (lime plus 

 carbon dioxide). 



As before stated, lime is not found un-com- 

 bined with other substances in nature. And 

 as it is of great economic importance, it will 

 be profitable to know how it is formed. Lime 

 is produced from ordinary limestone by burn- 

 ing it in kilns where it is subjected to a heat 

 of a certain temperature for a number of 

 hours. The heat drives off the carbon, dioxide, 

 which, as we have seen, has taken away from 

 each molecule of the compound all of the car- 



