A Chemistry Student approached the Master and asked, “Master, how do I achieve enlightenment in Chemistry?” The Master replied, “Wash your glassware.”

Introduction

Clean glassware is essential in chemistry. The problem is that the tolerance for shmutz varies with the work you are doing, and sometimes a chemist does not know how important clean glassware is to an experiment until it has failed. This document is designed to give an undergraduate chemistry student a brief introduction to what chemists mean by "clean" and how it can be achieved.

There are two broad degrees of clean in chemistry; quantitative and normal. Quantitatively clean glassware is required for the most demanding applications where a quantity is being measured at high precision, such in analytical or physical chemistry. Glassware at this level of cleanliness has no residues (e. g., grease) or other impurities on it. Normal clean glassware is free of large amounts of impurities, but some grease may be tolerated. Glassware that has been cleaned normally is used where high degrees of precision are not required, such as in a synthesis.

Tips

The key to cleaning is doing it a timely manner; letting dirty glassware sit for long periods of time guarantees a harder cleaning job. Also take a minute to separate your glassware into a group which requires a higher degree of cleaning and one that does not.

Disassemble your apparatus as soon as possible after you are finished with it. Remove all stopcocks and stoppers from aliition funnels, separatory funnels and the like. Ground glass stopcocks and stoppers will freeze in place if certain reactants (e. g., bases) were used in them. Triple rinse all surfaces with an appropriate solvent to remove traces of solvents and reaction mixtures, place these in the appropriate waste container.
Graduated cylinders, beakers, Erlenmeyer flasks, burets and pipettes that were only used to dispense or store reagents generally only need to be triple-rinsed with a compatible solvent followed by tap water and a final DI water rinse, if desired. Air dry on a drying rack. In some cases you may need to be more thorough, as described below.
Büchner funnels, etc. should be rinsed with an appropriate solvent to remove substances that are clinging to them. Follow this by tap water and DI water rinses and air dry.

Health and Safety Considerations

Even a task as simple as washing glassware at the sink is potentially hazardous. You must wear eye protection, appropriate for the task, at all times. Gloves are recommended, even for general cleaning, if the glassware contained an irritant, lachrymator or toxic material. Before cleaning be sure that any excess reagent has been disposed of properly and the vessel in which it was contained has been triple-rinsed into the waste container.

General Cleaning Procedure

The following steps should be followed for glassware for which a simple solvent rinse is not sufficient. If you need quantitatively clean glassware, these should be the first steps toward this goal, and more aggressive cleaning methods may be required ( vide infra).

The water will sheet cleanly off the glass, if it is quantitatively clean. If water does not sheet off the glass, and you desire the glassware to be quantitatively clean, first repeat the above soaking and scrubbing steps. If, after a second cleaning, bits of solid still adhere to the glass, or if there is clearly a greasy residue on the glass, more aggressive action must be taken.

More Aggressive Cleaning Methods

The following cleaning methods are two of the more commonly used ways to remove contaminants from glassware. They are usually used after normal cleaning has failed, and they are often used together, because each is effective at removing different types of contaminants. Care must be taken using either one because of the corrosive nature of the solutions used.

Glass fritted funnels and volumetric glassware can be soaked briefly with the base bath solution to remove small amounts of grease, but prolonged exposure to the caustic solution can damage these items.

Even More Aggressive Cleaning Methods

Sometimes 6 M HCl and a base bath are not sufficient, and even more aggressive methods must be employed. CAUTION! all of these methods will do severe damage to the eyes, skin, mucous membranes and lungs. Extreme caution should be exercised when using these methods. Wear butyl gloves ( NOT latex or nitrile exam gloves), eye protection and a lab coat. Work in the hood.

Undergraduate students must check with their faculty supervisor before using these methods, and they must be under the direct supervision of a faculty member at all times when using these methods (no exceptions).

How to Clean Glassware