Introduction
The glass weighing bottle, typically called Weighing Bottle or Weighing Bottle with Ground Glass Stopper, is a fundamental piece of laboratory glassware. It is a cylindrical vessel, usually made of borosilicate glass (for excellent thermal and chemical resistance), featuring a precise, matching ground glass stopper.
Its primary function is to enable the accurate weighing of solid samples-particularly those that are hygroscopic, volatile, or air-sensitive-on an analytical balance using the "weighing by difference" method. This design ensures the sample is protected from atmospheric moisture and contaminants during both weighing and storage.
Key Characteristics
1. Airtight Seal: The interchangeable ground glass stopper provides a secure, airtight seal. This is crucial for preventing samples from absorbing moisture from the air or undergoing unwanted reactions during the weighing process.
2. Chemical Inertness: Made from high-quality glass (especially borosilicate), the bottle is resistant to most chemicals. It does not react with or contaminate sensitive samples, ensuring weighing integrity.
3. Thermal Stability: Borosilicate glass weighing bottles can withstand repeated heating and cooling cycles. They are suitable for drying samples in an oven without cracking or degrading.
4. Design for Precision: Manufactured with uniform wall thickness and a stable base, its design minimizes buoyancy effects and ensures consistent, repeatable results on precision balances. Its low mass relative to its volume is also advantageous.
5. Transparency & Clarity: Clear glass allows for easy visual inspection of the sample's condition, level, and color without needing to open the bottle.
Common Types
Tall-form (High-form) Weighing Bottle: Has a taller, narrower body. Ideal for storing and weighing fine powders or valuable standards, as it facilitates easier pouring and reduces spillage risk.
Low-form (Flat-form) Weighing Bottle: Features a squat, wider body. Offers greater stability and easier access to the sample. Often preferred for drying samples in an oven due to better heat distribution.