44 LESSONS ON CHEMISTRY. 



salt cake of the glass manufacturer, and in the well-knoTvii 

 *' bakmg soda." It is the chief constituent of the ashes of 

 sea- weeds, is likewise found in the waters of several inland 

 lakes, and it also occurs in some countries covering the sur- 

 face of the land. 



Soda, like potash, is not a simple body, but a compound 

 of oxygen with Sodium, a rare metal, which in its separate 

 state is only to be found in the laboratory of the chemist.* 



45. Lime or quicklime is so well known to the farmer 

 that it is scarcely necessary to describe its characters. Like 

 potash and soda, it is a compound of a metallic body with 

 oxygen, being an oxide of a metal termed Calcium. It is 

 not met with in nature in a caustic state, but, combined with 

 carbonic acid, forming carbonate of lime (25) it is abundantly 

 diffused, and is found in every county in Ireland with the 

 exception of Wicklow, sometimes rising into great mountain 

 masses ; in other cases, as in the great central plain, forming 

 a subsoil of limestone gravel. Carbonate of lime, when pure, 

 as in statuary marble, has the following composition in the 

 hundred parts: — 



Lime . . . .56 

 Carbonic acid . 44 



100 

 When the compound is heated in the kiln, the carbonic 

 acid assumes its original form of gas, and escapes, the stone 

 losing 44 per cent, of its weight, and becoming caustic. A 

 piece of limestone, you are aware, will not dissolve in pure 

 water, but after buraing it becomes slightly soluble, and 

 dissolves in about 750 times its weight of water. 



46. Lime is also found in Ireland, and in many parts of 

 the world, combined with sulphuric acid (oil of vitriol) 

 and water. The compound is known as sulphate of lime, 

 gypsum, and plaster of Paris, and is raised for agricultural 

 purposes at Carrickmacross, in Monaghan. It also occurs 

 crystallized along the shore at Killroot, near Carrickfergus, 

 in Antrim. In England it is found in great abundance, in 

 several counties, in a compact state, and presenting various 

 shades of colour. It is so soft that it can be scratched easily 

 with the nail. The crystallized variety found near Carrick- 



* Common potash when exposed to the air attracts moisture and 

 becomes liquid (^deliquesces) while the common soda of the shops (car- 

 bonate of soda) crumbles down to a white powder (effloresces). 



