LAWS OF CHEMICAL COMBINATION

(a) Law of conservation of mass: "In all physical and chemical changes, the total mass of the reactants is equal to that of the products" or "matter can neither be created nor destroyed."

(b)Law of constant composition/definite proportion: "A chemical compound is always found to be made up of the same elements combined together in the same fixed ratio by weight".

(c) Law of multiple proportions: "When two elements combine together to form two or more chemical compounds, then the weight of one of the elements which combine with a fixed weight of the other bear a simple ratio to one another".

(d) Law of reciprocal proportions: The ratio of the weights of two elements A and B which combine with a fixed weight of the third element C is either the same or a simple multiple of the ratio of the weights of A and B which directly combine with each other. 

(e) Gay-Lussac's law of gaseous volumes: "When gases react together, they always do so in volumes which bear a simple ratio to one another and to the volumes of the products, if gaseous, all measurements are made under the same conditions of temperature and pressure".