SODA, LIMB AND MAGNESIA. 17 



Soda, We do not often see this substance by itself, 

 but almost always in combination with other bodies. 

 a. Some of the more common of these are carbonate of 

 soda, that is, the common washing soda of the shops; 

 and i' that is, common salt. Both 



of thi ain a large proportion of soda. 



6. It is white, atui wlien pure has the same attraction 

 for water, the same caustic and burning taste, as pot- 

 ash; in fact the two are much alike in many of their 

 properties, and also in the purposes which they seem 

 to serve in plants. 



Lime is a very common substance, and is well 

 known in all its usual forms, a. As quick or caustic 

 lime, it is of a white color, havine^ a strong burning 

 ta ' ' 1 austic pr It absorbs large 



q . and at tl. 'no becomes hot, 



faiii! lie powder. ! , when 



expnv, air, does not r> : caustic 



state, but drinks in moisture and crumbles gradually 

 away. b. In nature it is always found combined with 

 some other body, as, for instance, the common lime* 

 stone (car! * ' *' \ ♦■ ' 'ate of lime 

 (gypAiim, t»"th most 



a' • ^;en 



I . _ .mg 



(j wn and t'xplaineti. Every ton 



(1 , , . I- i"', t^sorKs one-fourth of a 



ton of water, which : the stone itself. 



Mat^esia is not so well k . although it 



is abundant on the earth's su::... many rocks. 



a. The most common and easily obtained form is the 

 calcined magnesia of the shops. This is a light, 

 whitr. tasteless substance, familiar to all who use much 

 I " T' salts, so vogue as a rae- 



. is anotht ind of magnesia. 



h. WltenburiH'ti, magnesia has something of the I 



