24 



PRINCIPLES OF CHEMISTRY 



Thus graphite, from which pencils are manufactured, is an element 

 with the lustre and other properties of a metal ; but charcoal and the 

 diamond, which are composed of the same substance as graphite, do 

 not show any metallic properties. Both classes of elements are clearly 

 distinguished in definite examples, but in particular cases the distinc- 

 tion is not clear and cannot serve as a basis for the exact division of 

 the elements into two groups. 



At all events, the conception of elements forms the basis of chemical 

 knowledge, and if we give a list of them at the very beginning of our 

 work, it is that we wish to symbolise the condition of the contemporary 

 information on the subject. Altogether about seventy elements are 

 now authentically known, but many of them are so rarely met with in 

 nature, and have been obtained in such small quantities, that we possess 

 but a very insufficient knowledge of them. The substances most widely 

 distributed in nature contain a very small number of elements. These 

 elements have been more completely studied than the others because a 

 greater number of investigators have been able to carry on experiments 

 and observations on them. The elements most widely distributed in 

 nature are : 



Hydrogen, H =1. In water, and animal and vegetable or- 

 ganisms. 



Carbon, C =12. In organisms, coal, limestones. 

 Nitrogen, N =14. In air and in organisms. 

 Oxygen, O =16. In air, water, earth. It forms the greater 



part of the mass of the earth. " 

 In common salt and in many minerals. 

 In sea-water and in many minerals. 

 In minerals and clay. 

 In sand, minerals, and clay. 

 In bones, ashes of plants, and soil. 

 In pyrites, gypsum, and in sea- water. 

 In common salt, and in the salts of MM 



water. 



K =39. In minerals, ashes of plants, and in nitre. 

 Ca = 40. In limestones, gypsum, and in organisms. 

 Fe =56. In the earth, iron ores, and in organisms. 

 Beside these, the following elements, although not very largely dis- 

 tributed in nature, are all more or less well known from their applicati< >ns 

 to the requirements of everyday life or the arts, either in a free state 

 or in their compounds : 



Lithium, Li =7. In medicine (Li. 2 C0 3 ), and in photography (LiBr). 

 Boron, B=l 1. As Borax, B 4 Na 2 O 7 , and as boric anhydride, B 2 O 3 . 



Sodium, Na=23. 

 Magnesium, Mg = 24. 

 Aluminium, Al =27. 

 Silicon, Si =28. 

 Phosphorus,? =31. 



Sulphur, 

 Chlorine, 



Potassium, 



Calcium, 



Iron, 



S 

 Cl 



= 32. 

 =35-5. 



= 39. 



