Gravimetric Determination of Arsenic
Determine the amount of arsenic present in soil samples.

The toxicity of arsenic has been known since antiquity, but it is still a cause of poisonings today; more than 1300 exposures to arsenic were reported in the United States in 1998, resulting in 4 fatalities. The biggest problem is the presence of arsenic in drinking water, especially in the country of Bangladesh, where most of the wells are contaminated. In this problem, you are going to use a simple procedure to determine the concentration of arsenic in two samples of contaminated soil. When groundwater flows through soil containing arsenic, some of the arsenic is transferred to the water. Although your real concern is the amount of arsenic in the drinking water, it is better to analyze the soil because the arsenic is more concentrated in the soil than in the water. In the samples you have in your lab, all the arsenic present in a 1.00 kg sample of soil has been converted to arsenate (AsO4-3). Design and perform an experiment to determine the amount of arsenate in the solutions, based on the following reaction, AsO4-3 + Ag+ => Ag3AsO4 (s) From your measurements, determine the mass percent of As in the soil.