One of the few sectors doing well right now is the specialty chemicals business. That’s because preservatives in foods, fertilizers for farms, compressed gasses for manufacturers and a host of other products have a built-in baseline demand. These are the building blocks for just about every product on the market, so chemical companies with well-run operations and a big reach have managed to find brisk business even in this tough climate.

I watch more than 5,000 publicly traded companies with my Portfolio Grader tool, ranking companies by a number of fundamental and quantitative measures. This week, I’ve got 4 chemical stocks to buy.

Here they are, in alphabetical order. Each one of these stocks gets an “A” or “B” according to my research, meaning it is a “strong buy” or “buy.”

Monsanto Co. (NYSE:MON) provides agricultural products to farmers and is based out of St. Louis. A modest gain of 4% has far outpaced the broader markets, as the Dow Jones is down .6% on the year.

Praxair Inc. (NYSE:PX) is a supplier of industrial gas. PX stock rounds out the list with a gain of 5% year-to-date. That gain is no small feat, especially amidst a volatile economic landscape.

Terra Nitrogen Co. (NYSE:TNH) is involved with the production of nitrogen fertilizer products. Like other stocks in the specialty chemicals sector, TNH stock is pleasing investors with a gain of 44% year-to-date.

W.R. Grace (NYSE:GRA) produces and sells specialty chemicals and specialty materials internationally. GRA stock has had an impressive 2011, jumping 8% year-to-date.

Get more analysis of these picks and other publicly-traded stocks with Louis Navellier’s Portfolio Grader tool, a 100% free stock-rating tool that measures both quantitative buying pressure and eight fundamental factors.