Summary: The Higher Secondary Chemistry Companion covers various topics such as the properties, changes, and classification of matter, air composition, hydrogen, water, compounds of nitrogen, gas laws, and chemical calculations. It also includes exercises for calculations from reacting weights of substances, equivalent weight, atomic weight, Faraday’s laws of electrolysis, acidimetry, and alkalimetry. The book discusses the preparation methods and uses of different chemicals, the law of constant proportions, and the preparation of gases like oxygen and methane. Experiments and reactions involving different compounds and elements like nitrogen, carbon, and phosphorus are explained along with their properties and uses. Examples of equations and chemical reactions are also provided.