CARBONATE OF LIME. 109 



the sulphate ; the former of these, especially, is a very 

 abundant substance, existing naturally in immense 

 quantities in the different forms of chalk and lime- 

 stone ; it is also very commonly an ingredient of the 

 soil, and constitutes a considerable part of the bones 

 of animals, and shells. 



228. As has already been stated (119), lime has a 

 less powerful attraction for carbonic acid, than it has 

 fof any other acid ; and therefore when we pour a 

 quantity of any acid over carbonate of lime, great 

 bubbling, or frothing "is occasioned by the escape of 

 the carbonic acid, which is set at liberty, when the 

 lime combines with the new acid (117). 



229. This bubbling, or effervescence, as it is called, 

 enables us very easily to ascertain whether a stone be 

 limestone or not, and likewise whether any particular 

 soil contains carbonate of lime ; for if any acid, such 

 as vinegar, does not occasion any effervescence, it is 

 certain that no carbonate of lime is present ; and if, 

 on the other hand, it does expel bubbles of gas, we 

 may be quite sure that a portion of some carbonate 

 is present, and by far the most common of these is 

 the carbonate of lime. 



230. All the forms of this substance are tasteless, 

 and quite insoluble in pure water ; but rain-water, 

 which commonly contains dissolved in it a very small 

 quantity of carbonic acid, has the power of dissolving 

 carbonate of lime : hence we commonly see the surface 

 of chalk or limestone appearing to be gradually cor- 

 roded, or worn away by the rain ; and for the same 



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