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The round-bottom flask is the workhorse of wet chemistry: reflux, distillation and high-temperature reactions all start here. In fused quartz, the round-bottom flask gains properties no borosilicate flask can offer — near-zero metal leaching, direct flame or furnace heating, and thermal shock resistance that tolerates rapid temperature changes during distillation and quenching.
Why quartz for round-bottom flasks
The spherical body distributes heat evenly, and in quartz that advantage extends to furnace temperatures: fused quartz flasks run continuously at 1050–1100°C. The extremely low thermal expansion of quartz (about 5.5×10⁻⁷/K) means the flask tolerates the localized heating of a burner or heating mantle without the stress failures common in ordinary glass. For trace analysis, the high purity of the material keeps the blank low.
Standard ground joints
Flask mouths can be finished with standard conical ground joints — common sizes include 14/23, 19/26, 24/29 and 29/32 — so the flask mates directly with condensers, dropping funnels, thermometer adapters and receiving flasks. PTFE sleeves or stoppers are recommended because quartz-to-quartz ground joints can seize under vacuum or alkali. Two-neck and three-neck variants, as well as pear-shaped and Kjeldahl-style bodies, are routinely made to order.
Typical applications
- Reflux and distillation of corrosive or high-purity media
- High-temperature reactions where borosilicate softens
- Sub-boiling distillation for ultra-pure acid preparation
- Ashing and digestion setups combined with quartz condensers
Using quartz flasks safely
Quartz flasks tolerate direct heating, but the usual rules of glassware still apply: avoid boiling dry against thick deposits, support the flask correctly, and never use quartz with hydrofluoric acid or hot concentrated phosphoric acid. Above roughly 1100°C, surface contamination (including fingerprints) accelerates devitrification — the glass gradually turns opaque as cristobalite forms — so clean handling extends service life.
Specifying
Capacities commonly run from 100 mL to 5000 mL. When ordering, state the joint size and position, neck count, wall preference and whether matching condensers or adapters are needed — sets are best ordered together so the joints are ground as matched pairs. GKLQuartz builds laboratory quartzware to drawing; send your sketch or sample via the Request a Quote page.
