THE UNION
Article 91: Power of the Deputy Chairman or other person to perform the duties of the office of, or to act as, Chairman
(1) While the office of Chairman is vacant, or during any period when the Vice-President is acting as, or discharging the functions of, President, the duties of the office shall be performed by the Deputy Chairman, or, if the office of Deputy Chairman is also vacant, by such member of the Council of States as the President may appoint for the purpose.
(2) During the absence of the Chairman from any sitting of the Council of States the Deputy Chairman, or, if he is also absent, such person as may be determined by the rules of procedure of the Council, or, if no such person is present, such other person as may be determined by the Council, shall act as Chairman.
About Constitution of India
WE, THE PEOPLE OF INDIA, having solemnly resolved to constitute India into a SOVEREIGN SOCIALIST SECULAR DEMOCRATIC REPUBLIC and to secure to all its citizens: JUSTICE, social, economic and political; LIBERTY of thought, expression, belief, faith and worship; EQUALITY of status and of opportunity; and to promote among them all FRATERNITY assuring the dignity of the individual and the unity and integrity of the Nation; IN OUR CONSTITUENT ASSEMBLY this twenty-sixth day of November, 1949, do HEREBY ADOPT, ENACT AND GIVE TO OURSELVES THIS CONSTITUTION