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Effects of Chemical Contamination on Aluminum Potassium Sulfate Crystal Growth

CSEF · 2002 Chemistry

Annie T. Thomas · Piedmont High School, Piedmont

Overview

Objectives/Goals The goal of this experiment was to determine the effects of contamination on the growth of aluminum potassium sulfate crystals. Methods/Materials Saturated aluminum potassium sulfate solutions were contaminated with each of four contaminants: potassium ferricyanide, chromium aluminum potassium sulfate, nickel sulfate,and copper sulfate. They were seeded with small, pure aluminum potassium sulfate crystals, and growth was measured daily in centimeters. Control crystals were also monitored. Results The crystals grown from the contaminated solutions were generally not affected in appearance, but their growth rates were altered. With 0.5 gram of contamination, the growth was slowed by 33 percent. With 1 gram of contamination, the growth was slowed by 66 percent. The chromium aluminum potassium sulfate was the contaminant that affected appearance. The color was a cross between the aluminum potassium sulfate and the chromium aluminum potassium sulfate. When 1 gram of copper sulfate or nickel sulfate was used, the seed dissolved completely. Potassium Ferricyanide created a visible layer over the seed crystals. Conclusions/Discussion The hypothesis tested was that contamination would result in smaller crystals, and this experiment supported it. The experiment provided knowledge of some effects of contamination on crystal growth. Another connection with this experiment is in electronics. The properties of contaminated crystals are extremely important in creating semiconductor devices. Contamination can create positive or negative charges, which can be directed through wire as an electrical current. This experiment expands knowledge in chemistry by showing how chemicals can crystalize and behave differently depending on their surrounding environment.

Summary statement

Aluminum Potassium Sulfate (alum) crystals were grown from contaminated alum solutions to understand the effects of contamination on the resulting crystals.

Help received

My grandfather helped me to buy the chemicals I needed for this experiment.

Competition history

  • CSEF 2002 Chemistry · Entry S0525

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