34 



The sulphates do not occur in any large quantity, but the alkaline 

 sulphates are regular constituents of the chief body fluids. 



A little fluorine occurs combined as calcium fluoride in the teeth 

 and bones. 



Among the inorganic bodies must also be classed hydrochloric 

 acid, which occurs in the secretion of the stomach, and carbon dioxide, 

 present in the blood and body fluids as well as in the expired 

 air. 



Organic Compounds. These are compounds of carbon with hydro- 

 gen, oxygen, and in some cases nitrogen. Phosphorus, sulphur, iron, 

 chlorine, iodine, may also enter into the composition of the various 

 organic compounds, of which there are three chief groups, proteins, 

 fats and lipoids, and carbohydrates. In addition there are the pro- 

 ducts of the breaking down of these bodies within the organism. 



The carbon atom is tetravalent that is to say, it can combine 

 with four atoms of another element (for example, hydrogen) to 

 form such a body as CH 4 , which is methane, or marsh-gas. Another 

 fundamental property of the carbon atom is that it can unite with 

 other carbon atoms to form a chain or a ring, thus giving rise to 

 the possibility of a large number of very complicated bodies, the 

 molecules of which are united together through the carbon atoms 

 contained in them. There are also rings composed of carbon and 

 nitrogen. 



1. Starting from methane, CH 4 , by the addition of one atom of 

 oxygen, 



H H H OH 



\ / \/ 



C +0- C 



/ \ /\ 



H H H H 



Methane Methyl alcohol 



we obtain an alcohol, methyl alcohol, HCH 2 OH, which, as it contains 

 t-he group CH 2 OH, is termed a primary alcohol. If we start from 

 propane, CH 3 CH 2 CH 3 , the compound two above methane in the 

 hain, 



CH,OH CH 3 



CH 2 CHOH 



CH 3 CH 3 CH 3 



Propane Primary propyl Secondary propyl 



alcohol alcohol 



the formulae show that it is possible to obtain two monatomic alcohols 

 (alcohols containing one OH group): one the primary alcohol (primary 

 propyl alcohol, as it is termed), containing the group CH^OH; the 

 other with the group CHOH characteristic of a so-called secondary 

 r.lcohol secondary propyl alcohol. 



