Materials Included In Kit

Additional Materials Required

Prelab Preparation

• Lead Testing Solution A has a shelf-life of about one month.
• Lead Testing Solution B has a shelf-life of about one day. Be sure to mix Solution B on the day it will be used just prior to the first use. The dry materials for both solutions have been premeasured for your convenience. Simply add 100 mL of distilled water to each bottle and swirl until all the materials have dissolved. Cap the bottles and store in a dark, cool place when not in use.

Safety Precautions

The purpose of this laboratory is to carefully test for the presence of lead—not to be contaminated by it! Caution students to handle all items with care and to follow test directions carefully. Students should wash their hands thoroughly upon completion of the laboratory testing. Lead Testing solutions A and B are toxic by ingestion and are eye and skin irritants. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. Solutions may be flushed down the drain according to following Flinn Suggested Disposal Method #26b. Solid lead items may be treated according to Flinn Suggested Disposal Method #27d. If lead is found in items from the student’s environment, contact local authorities for further laboratory testing and proper treatment procedures.

Teacher Tips

• Enough materials are provided in each lead test kit to conduct 100 tests. Each test can be completed in a five-minute period of time.
• Lead Testing Solution B is sensitive and has a short shelf-life. Make it fresh immediately before use. The powder in the bottle can be divided and used in smaller batches, if desired. Use less water in proportion to the amount of powder used.
• If lead is found in student-tested items it might represent widespread lead contamination. Contact local authorities for more precise laboratory testing and expertise for removal of any lead-containing items.
• The solutions used in this lead testing procedure are designed for testing hard surfaces and not liquids. If a cotton swab is dipped in Lead Testing Solution B and then into a liquid, it is possible to detect lead as the cotton swab air dries. It will turn pink or red just like the filter paper test but will not be totally accurate for sensing very small lead amounts in solution.

Introduction

Lead contamination is considered a very serious problem requiring immediate action, especially if small children are involved. How can lead be detected? Test some items from your environment.

Concepts

• Lead contamination
• Lead testing

Background

Lead is an odorless, tasteless, soft gray metal. It is very malleable and has little mechanical strength. It has a low melting point (327.5 °C) and a high resistance to corrosion. It is not found in nature in its metallic state, but rather as an ore, primarily galena (PbS). Lead readily forms alloys with tin, antimony, and other metals.

Lead has an interesting history. It was probably one of the first metals to be smelted and molded into objects since it can be smelted at temperatures occurring in campfires. There is evidence that during the time of the Roman Empire lead poisoning might have been significant in the society since lead containers were widely used for food and beverage preparation, food storage, and in plumbing fixtures. Lead in the environment increased markedly following the Industrial Revolution. This resulted in an estimated 500-fold increase in lead in human skeletons. Current annual lead production is about five million metric tons with the largest single use being in storage batteries.

The toxicology of lead poisoning is complicated. Lead is a general metabolic poison and it accumulates in the body over time. It can build up concentration in the bones and be remobilized long after it was absorbed by the body. Lead inhibits enzyme systems necessary for the formation of hemoglobin that is so vital to normal body function.

Marked differences exist in lead absorption in children compared to adults. Children can absorb 5–10 times more lead than adults. Symptoms and effects of lead absorption range from reduced birth weight at 10 mcg/dL (micrograms per deciliter) blood, to peripheral nerve dysfunction at 50 mcg/dL, to death at 125 mcg/dL of blood. Many serious effects may also result at intermediate lead concentrations.

Lead poisoning can occur through soil, air, food, water, tobacco, paint or other manufactured products. Except for occupational exposures, the largest source of lead contamination occurs due to ingestion of lead-containing substances. Children may ingest lead from paint chips or from lead contaminated soil or dust. Many additional sources of dietary lead are in our environment. Acidic foods can leach lead from tin cans. Ceramic pottery may be a source of lead. Cosmetics, folk medicines and hair dyes may also contain high levels of lead. Corrosion of plumbing and lead-soldered joints can result in drinking water with elevated lead levels. New EPA standards require that concentration of lead in water not exceed 15 parts per billion.

Materials

Safety Precautions

The purpose of this laboratory is to carefully test for the presence of lead—not be contaminated by it! Handle all solutions and objects with care and follow directions carefully. Wash hands thoroughly with soap and water before leaving the laboratory. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Procedure

1. Lead Testing Procedure
   1. Use a Beral-type pipet to soak a piece of filter paper with Lead Testing Solution A.
   2. Press the wet paper onto the surface to be tested, taking care to make good surface contact. Hold the paper firmly against the test surface. Allow the paper to stay in contact with the test surface for at least one minute.
   3. Remove the filter paper from the surface and allow it to air dry.
   4. Use a clean Beral-type pipet and soak the test paper with Lead Testing Solution B. The test paper should turn a bright orange initially. Any lead that is present is shown by the development of a pink or red color. If any pink coloration results, the lead content is considered to be in excess of 2%. The darker the red color, the more lead that is present.
2. Testing Objects
   1. Follow the lead testing procedure outlined above to test at least one item known to contain lead. Your instructor will have these items available.
   2. Follow the lead testing procedure to test at least two unknown items for the presence of lead. Select items from your environment that are of interest to you.
3. Consult with your instructor for appropriate treatment procedures.