SODIUM CHLORIDE BERTHOLLET'S LAWS 41 



bivalent elements, forming RH 2 , KO, RC1 2 , RHC1, R(OH)C1, R(OH) 2 , 

 R 2 C, RON, &c. Nitrogen in ammonia is the representative of the 

 trivalent elements, giving compounds RH 3 , R 2 3 , R(OH) 3 , RC1 3 , RN, 

 RHC, <fcc. In carbon are exemplified the properties of the quadrivalent 

 elements, forming RH 4 , RO 2 , RO(OH) 2 , R(OH) 4 , RHN, RC1 4 , RHC1 3 , 

 fcc. We meet with these forms of combination, or degrees of union of 

 atoms, in all other elements, some being analogous to hydrogen, others to 

 oxygen, and others to nitrogen or to carbon. But besides these quan- 

 titative analogies or resemblances, which are foretold by the law of 

 substitution (Chapter VI.), there exist among the elements qualita- 

 tive analogies and relations which are not fully seen in the compounds 

 of the elements which have been considered, but are most distinctly 

 exhibited in the formation of bases, acids, and salts of different types 

 and properties. Therefore, for a complete study of the nature of the 

 elements an.d their compounds it is especially important to become 

 acquainted, with the salts, as substances of a peculiar character, and 

 with the corresponding acids and- bases. Common table salt, or sodium 

 chloride, NaCl, may in every respect be taken as a type of salts in 

 general, and we will therefore pass to the consideration of this sub-; 

 stance, and of hydrochloric acid, and of the base sodium hydroxide, 

 formed by the non-metal chlorine and the metal sodium, which corre- 

 spond with it. 



Sodium chloride, Nad, the familiar table salt, occurs, although 

 in very small quantities, in all the primary formations of the earth's 

 crust, 2 from which it is washed away by the atmospheric waters ; it is 

 contained in small quantities in all waters flowing through these forma- 

 tions, and is in this manner conveyed to the oceans and seas. The 

 immense mass of salt in the oceans has been accumulated by this process 

 from the remote ages of the earth's creation, because the water has 

 evaporated from them while the salt has remained in solution. The salt 

 of sea water serves as the source not only for its direct extraction, but 



8 The primary formations are* those which do not bear any distinct traces of having 

 been deposited from water (have not a stratified formation and contain no remains of 

 animal or vegetable life), occur under the sedimentary formations of the earth, 'and are 

 everywhere uniform in composition and structure, the latter being generally distinctly 

 crystalline. If it be assumed that the earth was originally in a molten condition, the 

 first primary formations are those which formed the first solid crust of the earth. But 

 even with this hypothesis of the earth's origin, it is necessary to admit that the first 

 aqueous deposits must have caused a change in the original crust of the earth, and 

 therefore under the head of primary formations must be understood the most ancient of 

 the products of decomposition (mostly by atmospheric, aqueous, and organic agency, <6c.), 

 from which all the rocks and substances of the 'earth's surface have arisen. In speaking 

 of the origin of one or another substance, we can only, on the basis of facts, descend to 

 the primary formations, of which granite, gneiss, and trachyte may be taken as examples. 



