BARIUM, STRONTIUM, AND CALCIUM. 225 



tance from the particles of the lime that they are out of 

 the range of their attraction, and so they escape. The ef- 

 fect of heat is, you see, just opposite to that of solution, 

 the latter bringing particles more nearly together. The 

 carbonate of lime is quite in contrast with the carbonate 

 of potassium in this respect, for no heat, however great, 

 can drive the carbonic acid away from the potassium hy- 

 drate, as you learned in 287. And yet, strange as it may 

 seem, lime, as you also there learned, can take away the 

 carbonic acid from the potassium carbonate. 



312. Attraction of Lime for Water and Carbonic Anhydride. 

 The eagerness with which lime unites chemically with 

 water is shown in its slaking. So great is the heat pro- 

 duced by the rapid union that takes place that even gun- 

 powder has been ignited by it. It very readily ignites 

 phosphorus. Put a little quicklime in a heap upon a 

 board, and place on the top of it a bit of phosphorus. To 

 avoid wetting the phosphorus moisten the heap at the 

 bottom, and as the moisture spreads through the lime it 

 will very soon produce heat enough to set the phosphorus 

 on fire. Another experiment, showing the amount of heat 

 produced, may be tried as follows : Put some lime in a 

 bowl, and, moistening it, place a glass bell- 

 jar over it, Fig. 92. At first the steam 

 which rises from the slaking lime will be 

 condensed upon the inside of the glass. 

 But soon the heat will be so great that the - 

 steam in the bell-jar will form a transparent 

 atmosphere in it. If now you raise the Fig. 92. 



glass, the steam as it escapes loses its transparency, and 

 becomes a thick cloud, because it is changed into a kind of 

 fog by the condensing influence of the cold air. By the 

 union of lime with water there is formed a hydrate of lime, 

 there being in every 100 grammes of dry slaked lime about 



K2 



