- •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
Appendix B
Polymer Resistance
B.1 Introduction
The ability of polymers (plastics) to resist chemical attack is generally good. Obviously, some plastics canbetter resist some chemical types better than others. Unfortunately, theresults obtained from testing onechemical with onepolymer is not going to provide conclusive information on thesurvivability of an experimental setup because other factors such as heat, pressure, and internal (or external) stresses may play predominant parts. A polymer that normally indicates good compatibility (with a given chemical) mayfail outright. Thus, caution is advised, and pretesting, where possible, is recommended. These problems notwithstanding, knowing thecompatibility of a given polymer with a given chemical can significantly help a researcher or technician avoid early pitfalls.
The Nalge Company, manufacturer of Nalgene Labware, has performed extensive testing with the majority of industrial and laboratory plastics. With permission of the Nalge Nunc International Corporation, I have included the Chemical Resistance Chart from their catalog (seeTable B.I). In addition, I have preceded this table with a summary of their analysis on thevarious plastics tested. Formore information please contact:
Technical Service
Nalge Nunc International Corporation
Box 20365
Rochester, New York 14602-0365 (716)586-8800
The following are various plastic families and their respective specific plastics that are included in theChemical Resistance Chart. Theboldfaced uppercase letters correspond to the plastics in the chart. These acronyms are generally accepted, but arenotuniversal.
B.2 Polyolefins
The polyolefins are high-molecular-weight hydrocarbons. They include low-den- sity, linear low-density, and high-density polyethylene, polyallomer, polypropylene, and polymethylpentene. All are break-resistant, nontoxic, and
493
494 Polymer Resistance
noncontaminating. These plastics are the only ones lighter than water. They easily withstand exposure to nearly all chemicals at room temperature for up to 24 hours. Strong oxidizing agents eventually cause embrittlement. All polyolefins can be damaged by long exposure to UV light. The Chemical Resistance Chart details the following polyolefin types:
Polyethylene: The polymerization of ethylene results in the essentially branched-chain, high-molecular-weight hydrocarbon polyethylene. The polyethylenes are classified according to the relative degree of branching (side-chain formation) in their molecular structures, which can be controlled with selective catalysts.
Like other polyolefins, the polyethylenes are chemically inert. Strong oxidizing agents will eventually cause oxidation and embrittlement. They have no known solvent at room temperature. Aggressive solvents will cause softening or swelling, but these effects are normally reversible.
The following are a list of commonly used polyethylenes used in the lab: LDPE (low-density polyethylene).* These have more extensive branching,
resulting in a less compact molecular structure.
HDPE (high-density polyethylene).+ These plastics have minimal branching, which makes them more rigid and less permeable than LDPEs.
PP/PA (polypropylene/polyallomer). These plastics are similar to polyethylene, but each unit of their chains has a methyl group attached. They are translucent, autoclavable, and have no known solvents at room temperature. They are slightly more susceptible than polyethylene to strong oxidizing agents. They offer the best stress-cracking resistance of the polyolefins. Products made of polypropylene are brittle at ambient temperature and may crack or break if dropped from benchtop height.
PMP (polymethylpentene, "TPX™").* These plastics are similar to polypropylene, but have isobutyl groups instead of methyl groups attached to each monomer group of their chains. Their chemical resistances are close to those of PP. They are more easily softened by some hydrocarbons and chlorinated solvents. PMP is slightly more susceptible than PP to attack by oxidizing agents. PMP's excellent transparency, rigidity, and resistance to chemicals and high temperatures make it a superior material for labware. PMP withstands repeated autoclaving, even at 150°C. It can withstand intermittent exposure to temperatures as high as 175°C. Products made of polymethylpentene are brittle at ambient temperature and may crack or break if dropped from benchtop height.
PVC (polyvinyl chloride). These plastics are similar to polyethylene, but each of their units contain a chlorine atom. The chlorine atom renders PVC vulnerable to some solvents, but also makes it more resistant in many applications. PVC has extremely good resistance to oils (except essential oils) and very low permeability
*Formerly referred to as conventional polyethylene (CPE). f Formerly referred to as linear polyethylene.
*Registered trademark of Mitsui & Co., Ltd.
Appendix |
495 |
to most gases. Polyvinyl chloride is transparent and has a slight bluish tint. Nar- row-mouth bottles made of this material are relatively thin-walled and can be flexed slightly. When blended with phthalate ester plasticizers, PVC becomes soft and pliable, providing the useful tubing found in every well-equipped laboratory.
PS (polystyrene). These plastics are rigid and nontoxic, with excellent dimensional stability and good chemical resistance to aqueous solutions. This glassclear material is commonly used for disposable laboratory products. Products made of polystyrene are brittle at ambient temperature and may crack or break if dropped from benchtop height.
B.3 Engineering Resins
Engineering resins offer exceptional strength and durability in demanding lab applications. For specific uses, they are superior to the polyolefins. Typical products are centrifuge ware, filterware, and safety shields.
The following are a list of commonly used engineering resins used in the lab: NYL (nylon). Polyamide is a group of linear polymers with repeating amide linkages along their backbones. These polymers are produced by an amidation of diamines dibasic acids or by polymerization of amino acids. Nylon is strong and tough. It resists chemicals with negligible permeation rates when used with organic solvents. However, it has poor resistance to strong mineral acids, oxidiz-
ing agents, and certain salts.
PC (polycarbonate). These plastics are window-clear and amazingly strong and rigid. They are autoclavable, nontoxic, and the toughest of all thermoplastics. PC is a special type of polyester in which dihydric phenols are joined through carbonate linkages. These linkages are subject to chemical reaction with bases and concentrated acids, are subject to hydrolytic attack at elevated temperatures (e.g., during autoclaving), and make PC soluble in various organic solvents. For many applications, the transparency and unusual strength of PC offset these limitations. Its strength and dimensional stability make it ideal for high-speed centrifuge ware.
PSF (polysulfone). Like polycarbonate, PSF is clear, strong, nontoxic, and extremely tough. PSF is less subject than PC to hyrolytic attack during autoclaving and has a natural straw-colored cast. PSF is resistant to acids, bases, aqueous solutions, aliphatic hydrocarbons, and alcohols. PSF is composed of phenylene units linked by three different chemical groups: Isopropylidene, ether, and sulfone. Each of the three linkages imparts specific properties to the polymer, such as chemical resistance, temperature resistance, and impact strength.
496 |
Polymer Resistance |
B.4 Fluorocarbons |
|
Teflon® FEP (fluorinated ethylene propylene)* This material is translucent and flexible, and it feels heavy because of its high density. It resists all known chemicals except molten alkali metals, elemental fluorine, and fluorine precursors at elevated temperatures. It should not be used with concentrated perchloric acid. FEP withstands temperatures from -270°C to + 205°C and may be sterilized repeatedly by all known chemical and thermal methods. It can even be boiled in nitric acid.
Teflon® TFE (tetrafluoroethylene).* This material is opaque and white and has the lowest coefficient of friction of any solid. It makes superior stopcock plugs and separatory funnel plugs.
Teflon® PFA (perfluoroalkoxy).*This plastic is translucent and slightly flexible. It has the widest temperature range of the fluoropolymers — from -270°C to +250°C — with superior chemical resistance across the entire range. Compared to TFE at +277°C, it has better strength, stiffness, and creep resistance. PFA also has a low coefficient of friction, possesses outstanding antistick properties, and is flame-resistant.
Halar® ECTFE (ethylenechlorotrifluoroethylene)} This material is an alternating copolymer of ethylene and chlorotrifluroethylene. This fluoropolymer withstands continuous exposure to extreme temperatures and maintains excellent mechanical properties across this entire range (from cryogenic temperatures to 180°C). It has excellent electrical properties and chemical resistance, having no known solvent at 121°C. It is also nonburning and radiation-resistant. Its ease of processing affords a wide range of products.
Tefzel® ETFE (ethylenetetrafluoroethylene).* This plastic is white, translucent, and slightly flexible. It is a close analog of the Teflon fluorocarbons, an ethylene tetrafluoroethylene copolymer. ETFE shares the remarkable chemical and temperature resistance of Teflon TFE and FEP and has even greater mechanical strength and impact resistance.
PVDF (Kynar®polyvinylidene fluoride)} This plastic is a fluoropolymer with alternating CH2 and CF2 groups. PVDF is an opaque white resin. Extremely pure, it is superior for noncontaminating applications. Mechanical strength and abrasion resistance are high, similar to ECTFE. It resists UV radiation. The maximum service temperature for rotationally molded PVDF tanks is 100°C. Up to this temperature, PVDF has excellent chemical resistance to weak bases and salts, strong acids, liquid halogens, strong oxidizing agents, and aromatic, halogenated, and aliphatic solvents. However, organic bases and short-chain ketones, esters, and oxygenated solvents will severely attack PVDF at room temperature. Fuming nitric acid and concentrated sulfuric acid will cause softening. At temperatures
*Registered trademark of E.I. DuPont de Nemours & Co.
Registered trademark of Allied Corporation.
*Registered trademarks of Pennwalt Corp.