Specifications

Component List

All components listed below are included in this kit. Items marked Optional can be customized.

Available Joint Sizes · GB/ISO/ASTM Standards

All sizes share 1:10 standard taper — GB, ISO, and ASTM sizes are interchangeable

14/19 19/26 24/29 (GB·recommended) 29/32 34/35 · 45/40 · 50/42 custom

GB (Chinese) 14/19 · 19/26 · 24/29 · 29/32 ISO 14/19 · 19/26 · 24/29 · 29/32 ASTM (American) 14/20 · 19/22 · 24/40 · 29/42

* All components have matching joint sizes for full system compatibility. ASTM and GB/ISO sizes share 1:10 taper — seal lengths differ but are interchangeable.

Component	Standard Spec	Available Joint Sizes	Upgrade Options	Qty	Link
Please contact us to confirm the available specifications.

📌 Customization Notes:
• Joint size can be selected to match your existing lab system:
GB (Chinese): 14/19 · 19/26 · 24/29 · 29/32
ISO: 14/19 · 19/26 · 24/29 · 29/32
ASTM (American): 14/20 · 19/22 · 24/40 · 29/42
• Dropping funnel options: PTFE stopcock (standard) or vented PTFE stopcock (pressure equalization for smooth flow)
• Pressure-equalizing dropping funnel available for applications requiring extremely precise drop rate control
• Flask can be upgraded to three-neck for simultaneous addition, stirring, and inert gas introduction
• All optional specifications can be freely combined with no minimum order quantity
• For special requirements, please contact our technical team

💡 Recommended Add-Ons: Magnetic stirrer + stir bar · Thermometer (0–200℃) · Anti-bumping granules · Silicone tubing (Φ8mm × 2m) · Condenser cooling water connectors · PTFE stopcock spare parts

Product Description

I. Principle & Function

The reflux with dropping addition apparatus is a functional extension of the standard reflux setup. The key design feature is the integration of a dropping funnel into the reflux path via a three-way connector. This allows reagents to be added precisely and controllably to the reaction system during reflux without interrupting the process.

This design addresses several critical experimental needs:

Exothermic Reaction Control: Controlled addition rates allow heat to dissipate gradually, preventing localized overheating
Sequential Addition: Different reagents can be added in stages within a single reaction
Slow Addition: For extremely fast reactions requiring addition over hours
Inert Environment Addition: Reagents can be added under inert gas protection without breaking the inert atmosphere

✦ Comparison with Standard Reflux: Standard Reflux: Single addition, reflux throughout.
Reflux with Dropping Addition: Reflux with controlled, continuous reagent addition.
Best for: Reactions requiring rate control, stepwise addition, or unstable reagents that need to be added immediately before use.

II. Apparatus Components & Functions

Round-Bottom Flask — Main reaction vessel, single-neck or three-neck, capacity based on reaction scale
Spherical Condenser — Core reflux component; condenses vapor and returns it to the reaction system
Dropping Funnel — Key addition component; with ground joint and stopcock for precise rate control
Three-Way Connector — Connects flask, condenser, and dropping funnel; integrates reflux and addition paths
Heating Mantle (or Oil Bath) — Provides uniform, controllable heat
Iron Stand & Universal Clamps — Secure the apparatus, ensure vertical stability
Magnetic Stirrer (optional) — Provides stirring for uniform heat distribution

III. Dropping Funnel Stopcock Comparison

Glass Stopcock: Traditional design — requires vacuum grease lubrication. Advantages: heat resistant. Disadvantages: regular maintenance required, prone to leakage
PTFE Stopcock: Modern standard — no lubrication needed, chemical resistant, excellent seal, leak-free — the first choice for labs
PTFE Stopcock with Vent: Allows pressure equalization during addition, ensuring continuous, even drop flow without "air locking"

IV. Material & Workmanship

All glass components are manufactured from borosilicate glass 3.3. The dropping funnel stopcock is made from corrosion-resistant PTFE. All ground joints are precision-machined to the standard 1:10 taper, available in GB, ISO, and ASTM standard sizes.

This apparatus is designed and manufactured in compliance with GB/T 21298-2017 "Laboratory Glassware — Distillation Apparatus".

Applications

Typical Applications

Grignard Reagent Preparation

Slow addition of halide to Mg/THF — exotherm control

Acylation Reactions

Slow addition of acylating agents for rate control

Friedel-Crafts Reactions

Addition of acyl halides or alkyl halides to aromatic systems

Reduction Reactions

Slow addition of reducing agents (e.g., LiAlH₄, NaBH₄) solutions

Oxidation Reactions

Controlled addition of oxidants for selective oxidation

Step-Growth Polymerization

Controlled monomer addition for molecular weight control

Teaching Labs

Core hands-on technique teaching controlled addition

Reaction Type	Recommended Rate	Precautions
Please contact us to confirm the available specifications.

Operation & Maintenance

User Guide

The following is the standard operating procedure for the reflux with dropping addition apparatus. The addition operation is the core step — precise control of addition rate is critical.

🚨 Critical Sequence (DO NOT REVERSE):
Startup: Cooling water ON → Heat the flask → Establish stable reflux → Begin addition
Shutdown: Stop addition → Turn off heat → Cool → Turn off cooling water

I. Safety Check & Preparation

Inspect all glass components for cracks or chips
Work in a fume hood — wear lab coat, safety goggles, and gloves
Confirm the dropping funnel stopcock is closed; load the reagent to be added
Confirm the heating device (heating mantle or oil bath) is functioning properly
Prepare cooling water source with adequate flow

Standard assembly sequence (bottom to top)

Secure the round-bottom flask on the iron stand, positioned in the heating mantle
Add reactants to the flask — fill to 1/3 to 1/2 of flask capacity
Add 2–3 boiling stones or anti-bumping granules, or insert a magnetic stir bar
Attach the three-way connector to the flask
Install the spherical condenser on the top arm of the three-way connector (reflux path)
Install the dropping funnel on the side arm of the three-way connector (addition path) — ensure the ground joint is properly seated
Close the dropping funnel stopcock; add the reagent to be added
Secure the flask neck, condenser mid-section, and dropping funnel with universal clamps
The condenser top must remain open — vented to atmosphere (never seal!)

III. Cooling Water & Heating

Turn on cooling water first — follow bottom-in, top-out principle
Water flow should be slow and steady — excessive flow reduces heat exchange efficiency
Start heating the flask slowly to reflux the solvent
Once reflux is stable, prepare to begin addition

IV. Addition Operation (Critical Step)

Slowly open the dropping funnel stopcock to begin addition
Control the addition rate based on reaction exotherm and kinetics — common range 1 drop/second to 1 drop/5 seconds
For exothermic reactions: The key indicator is that the reaction temperature does not rise significantly. If temperature spikes, pause addition or reduce the rate
Monitor the reaction in the flask — color changes, gas evolution, precipitate formation — to track progress
Reflux should continue throughout addition — vapor condensing normally in the condenser
If addition causes reflux to cease, the rate is too fast or heating is insufficient — pause addition until reflux resumes

V. Post-Addition Reflux

After addition is complete, close the dropping funnel stopcock
Continue reflux for 30 minutes to several hours (based on reaction requirements) to ensure complete reaction
Continue stirring and heating until the reaction reaches completion

VI. Shutdown

After reaction completion, turn off the heating device first
Keep cooling water circulating until the apparatus cools to near room temperature
When no more condensate is returned, turn off the cooling water
Disassemble in reverse order
Clean all glassware thoroughly — pay special attention to the dropping funnel stopcock area
Dry and store properly

📌 Dropping Funnel Vent Operation: If using a dropping funnel with a vented stopcock, open the vent before starting addition to allow pressure equalization — liquid will flow continuously under gravity. Without venting, negative pressure inside the funnel will cause interrupted or erratic dropping.
For non-vented dropping funnels, loosen the addition port stopper for pressure equalization.

💡 From a Seasoned Lab Technician: The golden rule of addition is "Add slowly, watch constantly, heat steadily" — it's always better to add too slowly than to let the reaction run away.
For highly exothermic reactions (e.g., Grignard preparation, acylation), a pressure-equalizing dropping funnel is recommended for more precise rate control, avoiding the "sudden gush" that can occur when cracking open a stopcock.
If the flask shows sudden color change or temperature spike during addition — stop immediately, reduce heating, and use a cold water bath if necessary. This is the key operation for preventing runaway reactions.
After addition is complete, rinse the dropping funnel with a small amount of solvent to ensure quantitative transfer of all reagents.

Care & Notes

Show care & notes

⚠️ Safety & Compliance Checklist

Addition rate control

For exothermic reactions, carefully control addition rate to prevent runaway

Fire/explosion prevention

When refluxing flammable solvents, NO open flame — always use a heating mantle

Ventilation

All operations must be performed in a fume hood

Standard compliance

Apparatus design complies with GB/T 21298-2017

Do not

Condenser top must be vented: Never seal a reflux system — pressure buildup risks glass rupture
Anti-bumping: NEVER add boiling stones to a hot flask! Always cool first, then add

Reflux with Dropping Addition