PRINCIPLES OF CHEMISTRY INTRODUCTION

in nature are:—

Hydrogen,	H	=	1.	In water, and in animal and vegetable organisms.
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.
Sodium,	Na	=	23.	In common salt and in many minerals.
Magnesium,	Mg	=	24.	In sea-water and in many minerals.
Aluminium,	Al	=	27.	In minerals and clay.
Silicon,	Si	=	28.	In sand, minerals, and clay.
Phosphorus,	P	=	31.	In bones, ashes of plants, and soil.
Sulphur,	S	=	32.	In pyrites, gypsum, and in sea-water.
Chlorine,	Cl	=	35·5.	In common salt, and in the salts of sea-water.
Potassium,	K	=	39.	In minerals, ashes of plants, and in nitre.
Calcium,	Ca	=	40.	In limestones, gypsum, and in organisms.
Iron,	K	=	56.	In the earth, iron ores, and in organisms.

Besides these, the following elements, although not very largely distributed in nature, are all more or less well known from their applications to the