CLASSIFICATION OF ORGANIC SUBSTANCES. 307 



one (OH), and you have CCHHHHH(OH), which is the 

 same as C 2 H 5 (OH) or C 2 H 6 O, the formula for common 

 alcohol. This way of writing formulae has a great disad- 

 vantage : it does not bring out the idea of atomicity, so 

 we will repeat this explanation with graphic formulae. 

 (See 41 7.) 



II H 



I I 



H-C-H H-C-H 



I I 



H-C-H II-C-O-H 



I I 



II H 



Ethane. Common alcohol. 



Of course it makes no difference which atom of H in the 

 formula is replaced. This is a matter of theory solely, and 

 is apt when thus briefly treated to leave rather crude no- 

 tions, of which we must beg you to beware. 



423. Ethers. From what has been said it is evident that 

 if we regard (C 2 H 5 ) as a compound radical, alcohol may be 

 regarded as a hydrate; this similarity to the hydrates of 

 mineral chemistry is shown thus : 



Radical K Na (NH 4 ) (C a H 5 ) 



Hydrate KHO NaHO (NHJHO (C a H 5 )HO 



Alcohols may therefore be looked at in another light, 

 viz., as hydrates of organic radicals. 



Now if alcohols are hydrates, ethers are oxides. Here 

 again we must ask you to bear in mind that the term ethers 

 is a general one, applied to a great number of bodies sim- 

 ilar in constitution to common ether, though not at all 

 alike in other respects. You have probably been in the 

 habit of considering ether as a very mobile, volatile, odor- 

 ous, inflammable liquid used in medicine and photography ; 

 it will therefore be difficult to conceive of ethers which 



