Popular Science: The Magical and Sacred Glass Product — Laboratory Glassware
When people think of glass, they often associate it with beauty, describing it in poetic, dreamlike language: its crystalline transparency refracting the world’s splendor, captivating the senses; like morning dew and faint light, it’s not just a window’s garment but a magician of light and shadow, reflecting the beauty of all things; glass is like you, holding endless stories and purity within its essence… Yet, when you gently touch its watery-smooth surface, you find beautiful stories hidden within its transparent body.
Next, let’s explore the everyday glass objects that accompany us like a shadow, focusing on a more specialized but crucial category.
We refer to all glass products used for experiments, measurement, observation, and inspection in daily life, production, and scientific and technological fields collectively as laboratory glassware.
Properties of Laboratory Glassware: Since glassware is a container for holding chemical reagents or conducting chemical reactions, its ability to resist various chemical factors from the surrounding medium (chemical stability) is its most critical property. Laboratory glassware must also possess good thermal stability (resistance to thermal shock), mechanical strength, be transparent, and be easy to manufacture. Therefore, the key to ensuring the quality of glassware lies in producing glass that meets these requirements. Initially, instrument glass was made by adjusting the composition of soda-lime silicate glass to be high in silica, high in calcium, and low in alkali to improve its chemical corrosion resistance. Later, it was discovered that replacing part of the Na₂O in the glass composition with B₂O₃ not only acted as a flux but also significantly reduced the coefficient of thermal expansion, greatly enhancing the glass’s resistance to thermal shock. Through continuous research, development, and the introduction of components like zinc, barium, and magnesium, a series of borosilicate glass types for chemical apparatus emerged, meeting the performance requirements for laboratory glassware.
Classification of Laboratory Glassware: Laboratory glassware comes in a vast array of varieties. According to international standards, it is generally categorized into 8 types:
Delivery and Flow Control Devices: Glass joints, adapters, valves, stoppers, tubes, and rods.
Containers: Dishes, bottles, beakers, flasks, troughs, test tubes, etc.
Basic Operation Instruments and Apparatus: For absorption, drying, distillation, condensation, fractionation, evaporation, extraction, purification, filtration, separation, stirring, crushing, centrifugation, gas generation, chromatography, combustion, combustion analysis, etc.
Measuring Devices: Meters for flow, specific gravity, pressure, temperature, surface tension, etc., as well as volumetric flasks, graduated cylinders, pipettes, burettes, syringes, etc.
Physical Measurement Instruments: For testing color, light, density, electrical parameters, phase transition, radioactivity, molecular weight, viscosity, particle size, etc.
Instruments for Determining Chemical Elements and Compounds: For measuring arsenic, carbon dioxide, elemental analysis, functional group analysis, metal elements, sulfur, halogens, water, etc.
Material Testing Instruments: For measuring atmosphere, explosives, gases, metals and minerals, mineral oils, building materials, water quality, etc.
Food, Pharmaceutical, and Biological Analysis Instruments: For food analysis, blood analysis, microbial culture, microscope attachments, serum and vaccine testing, urine analysis, etc.
Types of Glass Used: Different types of laboratory glassware are made from glass compositions suitable for their intended use.
Low-expansion borosilicate glass (e.g., Pyrex): Offers excellent overall properties, particularly good thermal shock resistance and chemical stability. It is widely applicable and used in about 80% of laboratory glassware.
High-alumina, non-alkali borosilicate glass: Has a high usage temperature, mainly used for combustion tubes, high-pressure water gauges, etc.
Non-boric alkali-resistant glass: Used primarily for glassware under strong alkaline conditions and sometimes for boron determination apparatus.
Soda-lime glass: Low cost, used for simple-shaped items not requiring heating.
Vycor glass (high-silica glass) and Quartz glass: Offer superior properties (very high usage temperature, exceptional thermal shock resistance, UV transparency) but are expensive. Used for specialized applications demanding these characteristics. Pure quartz glass is also used for crucibles in refining semiconductors like silicon and germanium.
Manufacturing of Laboratory Glassware:
Small batches or complex shapes are often hand-formed.
Mass-produced items are made by machine blowing or pressing.
Uniformly sized products like glass tubes are formed using tube drawing machines.
The processes can be broadly divided into Hot Working and Cold Working:
Hot Working includes:
Glassblowing (Lampworking): Using primarily glass tubes, bending, blowing, pressing, and sealing are performed to make numerous instruments.
Sintering: Using glass powder or fibers as base material, compacted and sintered to create filter plates or crucibles of various porosities.
Secondary Tube Drawing: Processing original tubes into small-diameter, high-precision glass tubes.
Secondary Sheet Drawing: Processing original sheets into thin microscope slides and cover slips.
Cold Working primarily includes:
Grinding (e.g., Ground Glass Joints): Using standard molds and carborundum for coarse and fine grinding of glass openings, stoppers, etc., to create standard interchangeable joints and stoppers, widely used for tight connections.
Acid Etching for Graduations: Primarily used for marking lines and numbers on volumetric instruments. Sometimes, acid-resistant colored glazes or diffusion coloring are printed on the container surface and heat-treated to replace acid-etched lines and numbers.
Whether considering its vital importance in scientific research or its wide range of applications in industrial production, laboratory glassware has played a crucial role in the progress and development of human society.
