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Basic Practices for Wet Chemistry Labs
Appendix XI (adapted from NMSU Lab Guide - dls)

The safe use of basic laboratory equipment, such as glassware, is essential to day-to-day safety in the laboratory. Certain practices have been found to be effective in reducing the occurrence of accidents. Remember to use appropriate eye protection. The general rules are:


1. Never pipette by mouth. Always use a pipette bulb.

2. Never start a siphon by mouth.

3. Do not aim test tubes at your neighbor or yourself, especially when heating substances in them.

4. Wear a laboratory apron or laboratory coat. During hot weather an apron is usually more comfortable.

5. Dilution of acids and bases: always add the concentrated acid or base slowly to water. Never add water to concentrated acids or bases (explosive boiling may occur if you try to add water to the concentrated acid or base).

6. When reaction is anticipated or fumes are expected, perform transfers in a fume hood with the glass pulled down between your face and the reagents. Wear gloves. This will prevent contact with the reagents.

7. Pouring: touch a glass stirring rod against the lip of the vessel from which liquid is to be poured. The rod is placed into the receiving vessel and liquid is poured. The rod acts as a guide for the liquid and helps to eliminate splashing and splattering.


1. Use a flame (e.g., Bunsen burner) only for heating non-flammable solutions.

2. Use a boiling stone in a flask or heat directly under a stirring rod.

3. Never use an open flame in the same room with Class I solvents


Many laboratory accidents result from improper use of glassware. Widespread use of glassware tends to make users disregard the hazards associated with it. Caution should always be used when glassware is being handled.

A. Disposal - Cracked, chipped or broken glassware will not be used. Before being sent for repair or disposal, damaged glassware must be thoroughly cleaned and dried. If repair is impractical or dangerous, the damaged item should discarded according to the appropriate procedure.

B. Glass Tubing - Before using glass tubing, the ends must be fire-polished. When inserting glass tubing or thermometers into stoppers or other tubing, see that the hole is large enough to accommodate the glass. Thin-walled glass tubing will not be used for this purpose. lubricate both tube and stopper thoroughly with glycerin, soapy water, or water. Hold the stopper between the thumb and forefinger. Place the tubing in a grip-safe tubing manipulator close to the end to be inserted into the stopper. Twist the stopper into place. When stoppers and glass tubing become sealed together, they must not be separated by force. Either cut the stopper loose or discard the equipment.

C. Ground Glass Joints - Never try to force a frozen ground glass joint. A bottle stopper puller should be used to attempt dislodging of a frozen joint, or the glassware should be sent to a glass blower for removal.

D. Vacuum in Glass Equipment - Desiccators which are subjected to vacuum must be thoroughly shielded (i.e., taped) to prevent flying glass in the event of a failure. Glass assemblies that are operated under vacuum shall be shielded to protect employees from possible implosion. Thin-willed, flat-bottomed glass vessels must never be evacuated.

E. Pressure in Glass Equipment - The use of glassware for pressure work should be avoided. If approval to perform pressure work in glassware is granted through hazard safety reviews, adequate shielding must be provided to protect personnel from flying glass and contents of the equipment. Some type of relief device must be installed to prevent a buildup of excessive pressure. Materials having a boiling point below room temperature must not be run in sealed glass containers without adequate shielding. Reactions must not be run sealed glass containers without adequate shielding. In these cases, it must be assumed that the glass can shatter at anytime, and adequate protection from flying glass must be provided.

F. Storage - Glass apparatus will be stored so that the ends do not project beyond the shelves. Glass tubing shall be stored horizontally on shelves or in drawers.

G. Cleaning - All glassware used should be cleaned. Usually washing with detergent and rinsing is sufficient. A suitable brush may also help. Dry in air. Special cleaning may be required. Follow the instructor's guidelines for use of HCl and/or "cleaning solution". Remember to use eye protection. Never try to rinse glassware with alcohol/acetone. They have the potential to form a flammable mixture in air.


1. Never place your thumb over the end of a test tube. If you must seal it, use a stopper.

2. Make sure vacuum pumps and/or building vacuum lines have the proper check valves.

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Lab Safety Guide

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