Find the right long neck round bottom flask for Kjeldahl digestion, distillation, or nitrogen determinations. These borosilicate glass flasks vary in capacity and joint size, but share the long neck design that minimizes entrainment and simplifies handling during heating and cooling. This guide highlights five top options, clarifies who each product is best for, and explains key trade-offs to help you choose.
| Product | Capacity | Neck Type | Joint |
|---|---|---|---|
| stonylab Kjeldahl Flask, 500 ml | 500 ml | Long Neck | 24/40 outer joint |
| stonylab Kjeldahl Flask, 100 ml | 100 ml | Long Neck | 24/40 outer joint |
| Pyrex 800 mL Round Bottom Kjeldahl Flask, Long Neck | 800 mL | Long Neck | Not specified in title (Kjeldahl use) |
| DONLAB CMA-0250 Borosilicate Kjeldahl Flask, 250 ml | 250 ml | Long Neck | 24/40 ground glass joint |
| EISCO Kjeldahl Flask, 800 mL – Long Neck | 800 mL | Long Neck | Standard |
Note: All five options are designed to handle Kjeldahl digestion and related nitrogen determination tasks. The best choice depends on your maximum batch size, joint compatibility with your apparatus, and how often you handle glassware that requires long necks for venting and condensate control.
Stonylab 500 ml Kjeldahl Flask With Long Neck
The StonyLab 500 ml Kjeldahl Flask is constructed with heavy borosilicate glass and features a 24/40 outer joint for compatibility with standard condensers and adapters. It is commonly used as an air condenser during digestion and to reduce entrainment during distillation. Best for medium-scale nitrogen determinations and labs needing a robust, long-neck design that fits standard glassware.
Who this is best for: laboratories performing routine Kjeldahl digestion on batches around half a liter and needing reliable long-neck performance. Why chosen: the long neck helps manage vapors and condensates, while the 24/40 joint matches common lab setups. Caution: ensure matching condenser or adapter is available for your specific setup.
Stonylab 100 ml Kjeldahl Flask, Long Neck
This smaller long-neck variant is ideal for quick preliminary digestion tests or teaching labs needing compact, easily handled glassware. The 100 ml capacity and 24/40 joint support typical Kjeldahl workflows at reduced scale. Best for students or researchers running rapid nitrogen determinations or pilot tests.
Who this is best for: teaching labs or researchers performing small-scale Kjeldahl tests. Why chosen: compact size reduces waste and handling risk. Caution: lower capacity may not suit larger sample loads or higher-volume experiments.
Pyrex 800 mL Round Bottom Kjeldahl Flask, Long Neck
The Pyrex 800 mL Kjeldahl Flask offers a durable borosilicate design with long neck, suited for nitrogen determinations and Kjeldahl digestion. It emphasizes heat and chemical resistance, and permanent markings help resist chemical attack during lab usage. Best for labs requiring a well-known brand with strong thermal stability.
Who this is best for: replacement or standard equipment in research and teaching labs using the Kjeldahl method. Why chosen: reputable Pyrex brand with robust heat resistance. Caution: check joint compatibility with existing condensers if you require a precise fit.
DONLAB CMA-0250 250 ml Kjeldahl Flask, Long Neck
The DONLAB CMA-0250 offers a 250 ml capacity with a long neck and a standard 24/40 ground glass joint. This configuration supports Kjeldahl digestion and distillation workflows in mid-sized chemistry setups. Best for labs needing a reliable, mid-range capacity flask and a traditional ground glass joint.
Who this is best for: mid-sized laboratories or teaching labs requiring repeatable Kjeldahl digestion with a long-neck design. Why chosen: solid balance of capacity, joint compatibility, and durable borosilicate glass. Caution: ensure a compatible condenser and receiving adapter are on hand for full Kjeldahl workflow.
EISCO 800 mL Kjeldahl Flask, Long Neck
The EISCO 800 mL Kjeldahl Flask is designed for nitrogen determination consistent with the Kjeldahl method. Made of high-quality borosilicate glass and featuring a long neck, it serves medium to large scale digestion tasks. Best for labs seeking a dedicated Kjeldahl option from a specialized supplier.
Who this is best for: labs performing frequent Kjeldahl digestions at higher volumes while needing reliable glass with a long neck. Why chosen: explicitly designed for nitrogen determination workflows. Caution: verify joint compatibility with your specific distillation apparatus and condensers.
Buying Guide: Long Neck Round Bottom Flasks For Kjeldahl And Digestive Work
What to consider when choosing a long neck round bottom flask:
- Capacity: Match the flask size to your typical sample batch. Larger capacities (500–800 mL) suit medium to high-volume digestions; smaller flasks (100–250 mL) fit pilot tests or teaching labs.
- Neck length and design: A long neck helps reduce entrainment and simplify venting, especially during digestion and distillation. Confirm compatibility with your condenser, adapter, or receiving flasks.
- Joint size: Most Kjeldahl setups use 24/40 joints. Ensure the outer joint on the flask matches your condensers and glassware with no leaks. Some items list ground glass joints instead of standard taper joints.
- Material quality: Borosilicate glass offers good thermal shock resistance and chemical stability for standard lab solvent conditions. Look for reputable brands for consistent wall thickness and durable bottoms.
- Sealing and markings: Ground glass joints provide stable connections; permanent markings can resist chemical attack and improve labeling during workflows.
- Brand and compatibility: Established brands (Pyrex, EISCO, StonyLab, DONLAB) typically offer reliable production, but verify joint tolerances and your existing glassware compatibility before purchasing.
Frequently Asked Questions
- What is a Kjeldahl flask used for?
Used for nitrogen determination and digestion steps in Kjeldahl analysis, often paired with condensers and distillation systems. - Why choose a long-neck flask?
The long neck reduces entrainment, aids venting, and can improve condensate management during heating. - What joint size is common for Kjeldahl work?
The 24/40 standard taper joint is the most common for Kjeldahl setups, but confirm with your condenser and adapters. - Can these flasks be used for other chemical reactions?
They are primarily designed for Kjeldahl digestion, but borosilicate flasks can support various lab tasks that require round-bottom designs. - How do I select the right capacity?
Balance your typical sample size and batch processing needs; larger capacities support higher volumes but require larger heating equipment and more space. - Are all flasks hand-blown?
Several options are hand-blown or feature custom dimensions; verify provided dimensions if precise fit is critical for your setup.
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