This week, the ratings of four Chemicals stocks on Portfolio Grader are down. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

The Mosaic Company (NYSE:MOS) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Mosaic produces and distributes crop nutrients to the agricultural communities located in North America and other countries. MOS also rates an F in Portfolio Grader’s specific subcategory of Sales Growth. For a full analysis of MOS stock, visit Portfolio Grader.

Intrepid Potash, Inc. (NYSE:IPI) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). Intrepid Potash mines and markets potash for use as a fertilizer. The stock gets F’s in Earnings Revisions and Cash Flow. As of Sept. 6, 2013, 15.7% of outstanding Intrepid Potash, Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of IPI stock.

The rating of Olin Corporation (NYSE:OLN) slips from a C to a D. Olin Corporation manufactures and sells chlorine, caustic soda, sodium hydrosulfite, hydrochloric acid, hydrogen, sodium chlorate, bleach products, and potassium hydroxide. To get an in-depth look at OLN, get Portfolio Grader’s complete analysis of OLN stock.

The rating of Arabian American Development Company (NYSE:ARSD) declines this week from a C to a D. Arabian American Development owns and operates a petrochemical facility located in southeast Texas, which specializes in high purity petrochemical solvents and other solvent type manufacturing. The stock gets F’s in Earnings Momentum, Earnings Surprise, and Sales Growth. For a full analysis of ARSD stock, visit Portfolio Grader.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.