Salt, specialty chemicals, and automobile air bags may have nothing in common except if they make money for you. And they do have that in common for Chicago-based Morton International, whose operating profits of $276 million for the 1991 fiscal year ending June 30 exceeded its 1990 income by 15% on a 16% increase in sales to $1.9 billion. That's not too shabby a performance during a recession for a two-and-a-half- year-old firm. Morton International today is the product of a divorce of Morton and its onetime aerospace division, now the independent $1.3 billion-a- year Thiokol Corp., based in Ogden, Utah. What's more, Morton is not downsizing, like Du Pont, or ridding itself of large chunks of its chemical operations, like W. R. Grace. Overall employment levels are actually growing as the company adds people to its air bag systems manufacturing operations. The company still has a healthy appetite for small niche acquisitions that will ...