- •Contents
- •Foreword
- •Preface
- •1 Materials in the Lab
- •2 Measurement
- •3 Joints, Stopcocks, and Glass Tubing
- •4 Cleaning Glassware
- •5 Compressed Gases
- •6 High and Low Temperature
- •7 Vacuum Systems
- •8 The Gas-Oxygen Torch
- •APPENDIX
- •Appendix A Preparing Drawings for a Technician
- •Index
- •Foreword
- •Preface
- •For the Second Edition
- •Please note:
- •1 Materials in the Lab
- •1.1 Glass
- •1.1.1 Introduction
- •1.1.2 Structural Properties of Glass
- •1.1.3 Phase Separation
- •1.1.4 Devitrification
- •1.1.5 Different Types of Glass Used in the Lab
- •1.1.6 Grading Glass and Graded Seals
- •1.1.7 Separating Glass by Type
- •1.1.9 Stress in Glass
- •1.1.11 Tempered Glass
- •1.1.13 Limiting Broken Glass in the Lab
- •1.1.14 Storing Glass
- •1.1.15 Marking Glass
- •1.1.16 Consumer's Guide to Purchasing Laboratory Glassware
- •1.2 Flexible Tubing
- •1.2.1 Introduction
- •1.2.2 Physical Properties of Flexible Tubing
- •1.3 Corks, Rubber Stoppers, and Enclosures
- •1.3.1 Corks
- •1.3.2 Rubber Stoppers
- •1.3.3 Preholed Stoppers
- •1.3.4 Inserting Glass Tubing into Stoppers
- •1.3.5 Removing Glass from Stoppers and Flexible Tubing
- •1.3.6 Film Enclosures
- •1.4 O-Rings
- •1.4.2 Chemical Resistance of O-Ring Material
- •1.4.3 O-Ring Sizes
- •2 Measurement
- •2.1 Measurement: The Basics
- •2.1.1 Uniformity, Reliability, and Accuracy
- •2.1.2 History of the Metric System
- •2.1.3 The Base Units
- •2.1.4 The Use of Prefixes in the Metric System
- •2.1.5 Measurement Rules
- •2.2 Length
- •2.2.1 The Ruler
- •2.2.2 How to Measure Length
- •2.2.3 The Caliper
- •2.2.4 The Micrometer
- •2.3 Volume
- •2.3.1 The Concepts of Volume Measurement
- •2.3.2 Background of Volume Standards
- •2.3.4 Materials of Volumetric Construction #1 Plastic
- •2.3.5 Materials of Volumetric Construction #2 Glass
- •2.3.6 Reading Volumetric Ware
- •2.3.7 General Practices of Volumetric Ware Use
- •2.3.8 Calibrations, Calibration, and Accuracy
- •2.3.9 Correcting Volumetric Readings
- •2.3.10 Volumetric Flasks
- •2.3.11 Graduated Cylinders
- •2.3.12 Pipettes
- •2.3.13 Burettes
- •2.3.14 Types of Burettes
- •2.3.15 Care and Use of Burettes
- •2.4 Weight and Mass
- •2.4.1 Tools for Weighing
- •2.4.2 Weight Versus Mass Versus Density
- •2.4.3 Air Buoyancy
- •2.4.5 Balance Location
- •2.4.6 Balance Reading
- •2.4.7 The Spring Balance
- •2.4.8 The Lever Arm Balance
- •2.4.9 Beam Balances
- •2.4.10 Analytical Balances
- •2.4.11 The Top-Loading Balance
- •2.4.12 Balance Verification
- •2.4.13 Calibration Weights
- •2.5 Temperature
- •2.5.1 TheNature of Temperature Measurement
- •2.5.2 The Physics of Temperature-Taking
- •2.5.3 Expansion-Based Thermometers
- •2.5.4 Linear Expansion Thermometers
- •2.5.5 Volumetric Expansion Thermometers
- •2.5.7 Thermometer Calibration
- •2.5.8 Thermometer Lag
- •2.5.9 Air Bubbles in Liquid Columns
- •2.5.10 Pressure Expansion Thermometers
- •2.5.11 Thermocouples
- •2.5.12 Resistance Thermometers
- •3.1 Joints and Connections
- •3.1.1 Standard Taper Joints
- •3.1.2 Ball-and-Socket Joints
- •3.1.3 The O-Ring Joint
- •3.1.4 Hybrids and Alternative Joints
- •3.1.5 Special Connectors
- •3.2 Stopcocks and Valves
- •3.2.1 Glass Stopcocks
- •3.2.2 Teflon Stopcocks
- •3.2.3 Rotary Valves
- •3.2.4 Stopcock Design Variations
- •3.3.1 Storage and Use of Stopcocks and Joints
- •3.3.2 Preparation for Use
- •3.3.3 Types of Greases
- •3.3.4 The Teflon Sleeve
- •3.3.5 Applying Grease to Stopcocks and Joints
- •3.3.6 Preventing Glass Stopcocks and Joints from Sticking or Breaking on a Working System
- •3.3.7 Unsticking Joints and Stopcocks
- •3.3.8 Leaking Stopcocks and Joints
- •3.3.9 What to Do About Leaks in Stopcocks and Joints
- •3.3.10 General Tips
- •3.4 Glass Tubing
- •3.4.1 The Basics of Glass Tubing
- •3.4.2 Calculating the Inside Diameter (I.D.)
- •3.4.3 Sample Volume Calculations
- •4 Cleaning Glassware
- •4.1 The Clean Laboratory
- •4.1.1 Basic Cleaning Concepts
- •4.1.2 Safety
- •4.1.3 Removing Stopcock Grease
- •4.1.4 Soap and Water
- •4.1.5 Ultrasonic Cleaners
- •4.1.6 Organic Solvents
- •4.1.7 The Base Bath
- •4.1.8 Acids and Oxidizers
- •4.1.9 Chromic Acid
- •4.1.10 Hydrofluoric Acid
- •4.1.11 Extra Cleaning Tips
- •4.1.12 Additional Cleaning Problems and Solutions
- •4.1.13 Last Resort Cleaning Solutions
- •5 Compressed Gases
- •5.1 Compressed GasTanks
- •5.1.1 Types of Gases
- •5.1.2 The Dangers of Compressed Gas
- •5.1.3 CGA Fittings
- •5.1.4 Safety Aspects of Compressed Gas Tanks
- •5.1.5 Safety Practices Using Compressed Gases
- •5.1.6 In Case of Emergency
- •5.1.7 Gas Compatibility with Various Materials
- •5.2 The Regulator
- •5.2.1 The Parts of the Regulator
- •5.2.2 House Air Pressure System
- •5.2.4 How to Use Regulators Safely
- •5.2.6 How to Purchase a Regulator
- •6 High and Low Temperature
- •6.1 High Temperature
- •6.1.1 TheDynamics of Heat in the Lab
- •6.1.2 General Safety Precautions
- •6.1.3 Open Flames
- •6.1.4 Steam
- •6.1.5 Thermal Radiation
- •6.1.6 Transfer of Energy
- •6.1.7 Hot Air Guns
- •6.1.8 Electrical Resistance Heating
- •6.1.9 Alternatives to Heat
- •6.2 Low Temperature
- •6.2.1 TheDynamics of Cold in the Lab
- •6.2.2 Room Temperature Tap Water (=20°C)
- •6.2.8 Safety with Slush Baths
- •6.2.9 Containment of Cold Materials
- •6.2.10 Liquid (Cryogenic) Gas Tanks
- •7 Vacuum Systems
- •7.1 How to Destroy a Vacuum System
- •7.2.1 Preface
- •7.2.2 How to Use a Vacuum System
- •7.2.4 Pressure, Vacuum, and Force
- •7.2.5 Gases, Vapors, and the Gas Laws
- •7.2.6 Vapor Pressure
- •7.2.7 How to Make (and Maintain) a Vacuum
- •7.2.8 Gas Flow
- •7.2.9 Throughput and Pumping Speed
- •7.3 Pumps
- •7.3.1 The Purpose of Pumps
- •7.3.2 The Aspirator
- •7.3.3 Types and Features of Mechanical Pumps
- •7.3.4 Connection, Use, Maintenance, and Safety
- •7.3.5 Condensable Vapors
- •7.3.6 Traps for Pumps
- •7.3.7 Mechanical Pump Oils
- •7.3.8 The Various Mechanical Pump Oils
- •7.3.9 Storing Mechanical Pumps
- •7.3.11 Ultra-High Vacuum Levels Without Ultra-High
- •7.3.12 Diffusion Pumps
- •7.3.13 Attaching a Diffusion Pump to a Vacuum System
- •7.3.14 How to Use a Diffusion Pump
- •7.3.15 Diffusion Pump Limitations
- •7.3.17 Diffusion Pump Maintenance
- •7.3.18 Toepler Pumps
- •7.4 Traps
- •7.4.1 The Purpose and Functions of Traps
- •7.4.2 Types of Traps
- •7.4.3 Proper Use of Cold Traps
- •7.4.4 Maintenance of Cold Traps
- •7.4.5 Separation Traps
- •7.4.6 Liquid Traps
- •7.5 Vacuum Gauges
- •7.5.2 The Mechanical Gauge Family
- •7.5.4 The Liquid Gauge Family
- •7.5.5 The Manometer
- •7.5.6 The McLeod Gauge
- •7.5.7 How to Read a McLeod Gauge
- •7.5.8 Bringing a McLeod Gauge to Vacuum Conditions
- •7.5.10 The Tipping McLeod Gauge
- •7.5.11 Condensable Vapors and the McLeod Gauge
- •7.5.12 Mercury Contamination from McLeod Gauges
- •7.5.13 Cleaning a McLeod Gauge
- •7.5.14 Thermocouple and Pirani Gauges
- •7.5.15 The Pirani Gauge
- •7.5.16 Cleaning Pirani Gauges
- •7.5.17 The Thermocouple Gauge
- •7.5.18 Cleaning Thermocouple Gauges
- •7.5.19 The lonization Gauge Family
- •7.5.20 The Hot-Cathode Ion Gauge
- •7.5.21 Cleaning Hot-Cathode Ion Gauges
- •7.5.24 The Momentum Transfer Gauge (MTG)
- •7.6 Leak Detection and Location
- •7.6.1 AllAbout Leaks
- •7.6.3 False Leaks
- •7.6.4 Real Leaks
- •7.6.5 Isolation to Find Leaks
- •7.6.6 Probe Gases and Liquids
- •7.6.7 The Tesla Coil
- •7.6.8 Soap Bubbles
- •7.6.9 Pirani or Thermocouple Gauges
- •7.6.10 Helium Leak Detection
- •7.6.11 Helium Leak Detection Techniques
- •7.6.13 Repairing Leaks
- •7.7 More Vacuum System Information
- •7.7.1 The Designs of Things
- •8 The Gas-Oxygen Torch
- •8.1.2 How to Light a Gas-Oxygen Torch
- •8.1.3 How to Prevent a Premix Torch from Popping
- •8.2.2 How to Tip-Off a Sample
- •8.2.3 How to Fire-Polish the End of a Glass Tube
- •8.2.4 Brazing and Silver Soldering
- •Appendix
- •A.2 Suggestions for Glassware Requests
- •B.1 Introduction
- •B.2 Polyolefins
- •B.3 Engineering Resins
- •B.4 Fluorocarbons
- •B.5 Chemical Resistance Chart
- •C.1 Chapter 1
- •C.4 Chapter 4
- •C.5 Chapter 5 & Chapter 6
- •C.6 Chapter 7
- •C.7 Chapter 8
- •D.1 Laboratory Safety
- •D.2 Chemical Safety
- •D.3 Chapter 1
- •D.4 Chapter 2
- •D.5 Chapter 3
- •D.6 Chapter 4
- •D.7 Chapter 5 and the Second Half of Chapter 6
- •D.8 Chapter 7
- •D.9 Chapter 8
- •Index
236 Cleaning Glassware
4.1.3 Removing Stopcock Grease
Pre-preparation. Stopcock grease on a joint or stopcock must be removed before adequate soap and water cleaning can begin. It is always best to remove excess stopcock grease physically with a Kimwipe. Then, any film of stopcock grease remaining can be removed with less solvent.
Organic greases (i.e., Apiezon) can easily be removed with halogenated hydrocarbons, such as chloroform or methylene chloride. Methylene chloride is a minor suspected carcinogen and is therefore safer to use than chloroform, which is definitely a suspected carcinogen and known cause of liver damage. However, both of these are dangerous compounds and should be used in a fume hood. Acetone can also be used, but is not very effective on most stopcock greases. Heating glassware to about 400°C will also remove any organic greases. However, this heating may cause any remaining inorganic material to burn into the surface of the glass, which may prove very difficult to remove. Be sure to remove any Teflon items before heating because burning Teflon fumes are extremely toxic.
Silicone grease can be mostly removed with pentane or methylene chloride, but this technique leaves a film residue. Such a residue will not affect most chemical reactions, but can wreak havoc for any future glassblowing work. It cannot be stressed enough how completely silicone grease must be removed before any glasswork is to be done. Silicone grease can be effectively removed with a base bath (see Sec. 4.1.7), but this process is glass-destructive and should not be used with any volumetric ware. These greases cannot be removed with heat because the silicone itself will not burn off and any remains on the glassware can only be removed with approximately a three-minute soak in 5% to 10% HF.
Fluorocarbon greases (Krytox) originally required a chlorinated fluorocarbon for removal. In the last few years, it was found that an industrial solvent (such as BH-38 from Spartan Chemical Co.*) can remove Krytox. Tests that this author has conducted seem to show a film of some kind remains on the joint, so it is unknown exactly how safe it is to heat a joint or stopcock that has been cleaned with this technique. Do not use heat to remove Krytox because heating (> 260°C) will produce fumes (lethal fluorine compounds, such as HF) that are highly toxic. For more information on cleaning these greases, see Sec. 3.3.3.
4.1.4 Soap and Water
After the various greases are removed from the apparatus, it is then possible to continue with soap and water cleaning. However, whether organic solvents were used or not, glassware should be rinsed out first with a small amount of acetone and then water, before being placed in a soapy water solution.
Material. There is a variety of powdered and liquid washing compounds available on the commercial market that, when mixed with water, provide excellent cleaning. There are a few superconcentrated cleaners (that come as liquids) which
Their address is in Appendix C, Sec. C.4.
The Clean Laboratory 4.1 |
237 |
are excellent for cleaning items by long-term soaking.
Preparation. Because there are as many different preparation techniques as there are commercial brands, it is best to read the instructions on the container of the cleaner you are using.
Use. Soap-based cleaning products are generally long-chain hydrocarbons that are negatively charged at one end. The hydrocarbon end of the soap molecule does not dissolve in (polar) water, but combines with other soap molecules to form "sphere" like shapes called micelles. The outer surface of the "sphere" has a charged end which allows it to freely associate within water. However, the hydrocarbon end is still able to dissolve other hydrocarbons. Thus, one end can grab dirt and the other end can grab water. Soaps and detergents do not make an oil soluble in water, rather with the assistance of agitation they aid its emulsification.
Soaps and detergents make water "wetter" by lowering the surface tension of the water. In doing so, less energy is required to lift dirt off whatever it is on. Other agents within a cleaning solution may include materials that help emulsify oily matter, soften water, solubilize compounds, control pH, and perform other actions to assist the cleaning process.
In general, these cleaning compounds work better in warm or hot water. Some scrubbing with a test tube brush, sponge, or the like, is usually needed, but some of the liquid cleaners only require soaking the glassware overnight. Do not use any rough-surfaced material (i.e., pumice, kitchen cleanser, rough plastic, or metal scouring pads) that can scratch the glass. When glass is scratched, the rough surface provides an easier surface for contaminates to adhere to and is therefore much harder to clean (and maintain) in the future. This surface scratching is also why you should never use abrasive scouring cleansers on new porcelain surfaces in the home. If you do, you will destroy the surface and will have no recourse but to scour away in all future cleaning. In addition to cleaning problems, abraded surfaces make glass much easier to break.
Some people use a green scouring square, found in the kitchen on their glassware. These are wonderful in scratching off dirt, contamination, glass, and porcelain. These should not be used in the kitchen or the laboratory. Any scrubber that is identified as Teflon safe should be used in either the kitchen or the laboratory. There is a yellow scouring pad from the Arden Corporation* that is Teflon safe and that is particularly abrasive to dirt and leaves glass and porcelain untouched.
There is a nonabrasive scouring cleaner on the market called Bon Ami®. Most other cleansers contain silica as the abrasive agent. Bon Ami contains feldspar and calcium carbonate, which are softer than glass and therefore cannot scratch glass surfaces.
After cleaning, copiously rinse glassware with tap water and follow with a deionized (or distilled) water rinse. Let the glassware stand upside down for storage or to dry. If your freshly washed glassware needs to be immediately dried for an experiment, you may facilitate the drying by placing the glassware in a drying
*Their address is in Appendix C, Sec. C.4.
238 |
Cleaning Glassware |
oven. Alternatively, you may pour about 10 mL of reagent-grade acetone or methanol into the glassware, swirl it around, and pour the remains into a container labeled "used acetone" or "used methanol," which can then be used for future cleaning.
Safety Considerations. You should always wear safety glasses. Because most cleaning compounds can be drying to the skin, it would be wise to wear rubber gloves. Also, wearing gloves allows the use of hotter water. Hot water can facilitate and improve the cleaning action of most cleaners.
Disposal. These soaps and detergents may all be washed down the sink. Some of the older types contain phosphates and, due to environmental concerns, should be phased out, or used as little as possible. Additionally some concentrated liquid cleaners can be reused many times before they need to be disposed, so check the instructions before you discard a cleaner.
4.1.5 Ultrasonic Cleaners
Ultrasonic cleaners can loosen dirt particles off the walls of solid material and are essential if there is any particulate matter in small crevasses or corners where it would be otherwise impossible to reach.
Ultrasonic cleaning works by emitting a series of very high-pitched sound waves that create a series of standing waves in solution. The waves alternately compress and decompress the cleaning solution. During the decompression stage, the liquid outgasses and millions of tiny bubbles are formed. During the compression stage, the bubbles implode. This implosion (called cavitation) is the destructive force that loosens dirt particles.
To use an ultrasonic cleaner, immerse the item to be cleaned in the cleaning solution within the device's tank. There are general-purpose and industrialstrength cleaning solutions as well as specific cleaning solutions for jewelry, oxides, and buffing compound removers. Turn the ultrasonic cleaner on for several minutes, and see if your item is clean. If not, repeat the process and/or try an alternate cleaning method. After an item has been cleaned, rinse as you would with a soap and water wash.
Although uncommon, it is possible to damage glass items with ground sections in an ultrasonic cleaner. This damage can occur when items are left too long in the cleaner. Ground sections to be concerned about include ground joints, stopcocks, and even the lightly etched dots on flasks and beakers (used for writing on). The damage can range from simple cracks that radiate from the ground areas, to chipped-off pieces of glass.
One of the obvious restrictions with ultrasonic cleaners is that the object to be cleaned needs to be able to fit inside the cleaning tray. Commercial ultrasonic cleaners can be as small as 3V2*diameter and 3~ deep to as large as 19 3/4" x 1\"
The Clean Laboratory 4.1 |
239 |
4.1.6 Organic Solvents
There are three types of organic solvents that can be used for cleaning: nonpolar, polar, and the halocarbons. They are all capable of removing adsorbed (soaked into the walls of a container) contaminants.
Nonpolar solvents, such as hexane, can be used to dissolve nonpolar contaminants such as oils from glass.
Examples:
(various hydrocarbons)
Hexane
Ethane
Benzene
Polar solvents, such as the alcohols and ketones, are useful for the removal of polar contaminants, but also attach to adsorbed sites and thereby limit the amount of area available for undesirable materials. Thus, final rinses with polar hydrocarbons can be very beneficial.
Examples:
(various alcohols and ketones)
Ethanol
Methanol
Isopropanol
Acetone
Methyl ethyl ketone
Halocarbons, a class of polar solvents, are hydrocarbons with an attached halogen. There are commonly three types of halocarbon solvents: those based on chlorine, fluorine, and a combination of the two. They are all powerful degreasing materials and can be particularly effective in removing polar contaminants from glass. The chlorofluorocarbons are currently under review because they cause environmental damage to the ozone layer.
Examples:
(various fluorocarbons, chlorocarbons, and chlorofluorocarbons)
Trichloroethylene
Perchloroethylene
Methylene chloride (dichloromethane)
Trichlorotrifluoroethane
By adding small quantities of a hydrocarbon polar solvent to a chlorofluorocarbon, the overall cleaning abilities of both may be substantially improved.
Pre-preparation. Ascertain whether the contamination is polar or non-polar. Material. Dichloromethane or acetone are good places to start because of their