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I HAVE been led by my desire of avoiding circumlocution, 

 to make use of some terms in the following work, which 

 may require explanation. 



1. When the simple name of a compound occurs, it is 

 to be understood that it is a compound of one atom of 

 each constituent. Thus, oxide of zinc is a compound of 

 one atom zinc and one atom oxygen. Sulphuret of bis- 

 muth, a compound of one atom bismuth and one atom 

 sulphur. Sulphate of potash, a compound of one atom 

 sulphuric acid and one atom potash. 



2. When the acid which a salt contains is doubled, the 

 doubling is denoted by prefixing the Latin word bis to 

 the name. Thus, bisulphate of potash means a compound 

 of two atoms sulphuric acid and one atom of potash. Bi- 

 borate of soda is a compound of two atoms boracic acid 

 and one atom soda. 



3. When the base is doubled, this is denoted by pre- 

 fixing the Greek syllable dis. Thus, disulphate of alu- 

 mina is a compound of one atom sulphuric acid and two 

 atoms alumina. 



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