] 80 CHEMISTRY. 



Glauber Salts. 



Glauber salts (or sulphate of soda) are obtained by 

 distilling common salt with sulphuric acid : the resi- 

 due of this operation is Glauber salts. It is named 

 after Glauber, a German, its discoverer. 



Epsom Salts. 



Epsom salts (or sulphate of magnesia) are usually 

 obtained from the sea water, the residuum of which, 

 after the separation of common salt, is known by the 

 name of bittern, and contains sulphate and muriate of 

 magnesia. It was at one time procured from the 

 springs of Epsom, in Surrey, and whence its name. 



Chemical Tests. 



Alkalies change the colours of most flowers to 

 green, and acids to red. 



Insolubility. 



The distinguishing characteristic of all the natural 

 combinations of earths with each other, and with 

 acids, (alum and Epsom salts excepted) is insolu- 

 bility. 



Nitre Beds. 



Artificial nitre beds consist of the refuse of vege- 

 table and animal matter undergoing putrefaction, 

 mixed with calcareous and other earths. The air 

 furnishes the oxygen and azote, (or nitrogen,) which 

 are the component parts of nitric acid ; but how lime 

 contributes to their union is not known, and the ap- 

 pearance of the potash is equally extraordinary. 



Test of Alkali. 



The quantity of alkali present in any portion of 

 potash or barilla is directly in proportion to the 

 quantity of acid requisite to produce saturation. 



