Lonza Group will purchase Arch Chemicals Inc (ARJ) for $1.2 billion in cash to produce the global head in the industry of killing fungi and bacteria.On July 8, Lonza said in an e-mail statement the company plans to pay $47.30 a share, 12 percent more than the closing price for Arch Chemicals. Shares of Arch increased 11 percent on July 8.The purchase of the company has a "strong strategic rationale" since it permits both companies complementary dealings and increases the sales of Lonza in up-and-coming markets, according to Peter Welfotd, an analyst with Jeffries International Ltd in London.