The overall ratings of five chemicals stocks are down on Portfolio Grader this week. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, The Mosaic Company (MOS) falls to a D (“sell”), worse than last week’s grade of C (“hold”). 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 more information, get Portfolio Grader’s complete analysis of MOS stock.

Intrepid Potash, Inc.’s (IPI) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). Intrepid Potash mines and markets potash for use as a fertilizer. The stock gets F’s in Earnings Revisions and Cash Flow. The stock price has fallen 9.5% over the past month, worse than the 1.7% decrease the S&P 500 has seen over the same period of time. As of Dec. 20, 2013, 15.9% of outstanding Intrepid Potash, Inc. shares were held short. The stock has a trailing PE Ratio of 26.20. To get an in-depth look at IPI, get Portfolio Grader’s complete analysis of IPI stock.

This week, Olin Corporation’s (OLN) rating worsens to a D from the company’s C rating a week ago. Olin Corporation manufactures and sells chlorine, caustic soda, sodium hydrosulfite, hydrochloric acid, hydrogen, sodium chlorate, bleach products, and potassium hydroxide. As of Dec. 20, 2013, 19% of outstanding Olin Corporation shares were held short. For a full analysis of OLN stock, visit Portfolio Grader.

The rating of Arabian American Development Company (ARSD) slips 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 more information, get Portfolio Grader’s complete analysis of ARSD stock.

This week, PetroLogistics LP (PDH) drops from a C to a D rating. PetroLogistics owns and operates propane dehydrogenation facility that processes propane into propylene. The stock price has fallen 9.8% over the past month. To get an in-depth look at PDH, get Portfolio Grader’s complete analysis of PDH stock.

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.