Coors* 99.8% Alumina Crucible Covers

NOTE: Due to unavoidable variations in manufacturing processes, cover may not fit precisely on crucibles. CoorsTek AD-998 Labware is made of 99.8%-pure aluminum oxide. Highly resistant to chemical attack, this alumina-ceramic ware is especially useful to chemists, metallurgists and others involved in high-temperature work demanding contamination-free results. AD-998 ware is highly refractory, meant for use in reducing and oxidizing atmospheres. It is inert in hydrogen and carbonaceous atmospheres and offers high resistance to alkalies and other fluxes. Suitable for glass melting, including borosilicate glass. Recommended for use with refractory metals such as molybdenum, platinum, rhodium, tungsten, tantalum and iridium. High-Alumina Labware temperature change rate should not exceed 150ºC/hour.
Typical physical properties follow:
Maximum Use Temperature (No Load) 1750°C
Thermal-Expansion Coefficient (25°-1000°C) 8.0 x 10-6/°C
Compressive Strength >300,000 psi
Specific Gravity 3.9 (Typical)
Hardness 79 on Rockwell 45N scale
9 on Mohs scale
Permeability Gas-tight
Water Absorption None
Chemical Tests Hot concentrated sulfuric acid, 100°C, 4 hrs.: weight loss ~6x10-4%
(65503 Crucible A 32g weight) Hot 10% sodium hydroxide, 100°C, 4 hrs.: weight loss ~9x10-4%
Hot 50% phosphoric acid, 90°C, 4 hrs.: weight loss ~0.16%