The board may sell such bonds from time to time in such quantities as may be necessary and most advantageous to raise the money for the construction of such canals and works, the acquisition of property and rights and otherwise to fully carry out the object and purposes of sections 46-101 to 46-1,111. Before making any sale, the board shall at a meeting, by resolution declare its intention to sell a specified amount of the bonds and the day and hour and place of such sale, and shall cause such resolution to be entered in the minutes, and notice of the sale to be given by publication thereof at least twenty days in a daily newspaper published in each of the cities of Omaha and Lincoln, and in any other newspaper, at its discretion. The notice shall state that sealed proposals will be received by the board at its office, for the purchase of the bonds, till the day and hour named in the resolution. At the time appointed the board shall open the proposals and award the purchase of the bonds to the highest responsible bidder, and may reject all bids; Provided, however, that if no bids have been received or submitted up to such time, the board may proceed to negotiate for the sale of the bonds, and may adjourn to some specific date, from time to time, or to convene at the call of the president, to consider such negotiations and all subsequent or new proposals, and may at such adjourned meeting, award the purchase of the bonds, or a portion thereof, to the highest responsible bidder submitting proposals thereat, or may reject all bids; Provided, however, that the board shall in no event sell any of the bonds for less than ninety percent of the face value thereof.