Dow Chemical Company agreed to buy Rohm & Haas Co. for about $18.8 billion, reducing its dependence on petroleum-based commodity chemicals and increasing sales of more profitable products. Financing for the deal includes equity investments of $3 billion by Berkshire Hathaway Inc. and $1 billion by the Kuwait Investment Authority, the company said. Chief Executive Officer Andrew Liveris has said he has been seeking a large acquisition that would reduce Dow’s dependence on swings in the pe...