Laboratory flasks are specialized glass vessels with narrow necks and wider bases, used for mixing, heating, distilling, titrating, and storing liquids in chemistry, biology, and analytical labs. The 14 most common types include the Erlenmeyer flask (mixing without splashing), Florence flask (even heating), round-bottom flask (distillation and reflux), volumetric flask (precise dilution to ±0.05%), Büchner
Fused silica and fused quartz are both non-crystalline forms of silicon dioxide (SiO₂) — chemically identical but distinguished by purity, manufacturing route, and OH content. Fused quartz is made by melting naturally occurring crystalline quartz at 2,000+ °C; fused silica is synthesized from gaseous SiCl₄ via flame hydrolysis or plasma deposition, producing higher purity (≥
Glass hardness is measured by four standard methods: the Mohs scratch test (qualitative, 5.5 for soda-lime, 6 for borosilicate, 7 for quartz), the Knoop hardness test (HK, used for brittle materials per ASTM C730), the Vickers hardness test (HV, with a diamond pyramid indenter per ASTM C1326), and the Brinell test (rarely used on glass).
To tell glass from quartz, use 5 quick tests: (1) UV transmission — quartz transmits UV-C down to 170 nm, glass blocks below 320 nm; (2) thermal shock — quartz survives 1,100 °C → ice water; glass shatters above 200 °C ΔT; (3) Mohs scratch — quartz scratches glass (7 vs 6); (4) thermal expansion
One of the most important thermal properties of fused quartz is its extremely low coefficient of thermal expansion: 5.5 x 10-7 /°C (20-320 °C). Its coefficient is 1/34 that of copper and only 1/7 of borosilicate glass. This makes the material particularly useful for optical flats, mirrors, furnace windows and critical optical applications which require minimum
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