Introduction
A dropping funnel or addition funnel is a type of laboratory glassware used to transfer liquids. They are fitted with a stopcock which allows the flow to be controlled. Dropping funnels are useful for adding reagents slowly, i.e. drop-wise. This is desirable when the quick addition of the reagent results in side reactions, or if the reaction is too vigorous.[1]
Dropping funnels are usually constructed with a ground glass joint at the bottom, which allows the funnel to fit snugly onto a round bottom flask. This also means it need not be clamped separately.[1]
Dropping funnels have been in use since at least the mid-1800s.[2]
Pressure-equalizing dropping funnels: have an additional narrow-bore glass tube from the bulb of the funnel, to the ground glass joint around the stem. These replace the liquid volume lost in the bulb with the equivalent gas volume from the flask into which the reagent is flowing, and are useful when handling air-sensitive reagents in a sealed, inert-gas environment. Without this tube, or some other means to equalize the pressure between a sealed receiving flask and the bulb of the funnel, the flow of fluid from the bulb will rapidly come to a halt.[1]
Simple dropping funnel: A dropping funnel consists of a (often) graduated cylindrical tube or in some models pear-shaped bulb, with a female ground glass joint on its top, where a stopper, either PP or glass is used. The lower part of the funnel has a stopcock, glass or PTFE which allows the flow to be controlled. he dripping tube is separate from the ground glass joint and extends a bit below the joint. Dropping funnels are similar in construction to separatory funnels, though the main difference is that separatory funnels don’t have a male ground glass joint.
: this is the iconic dropping funnel, it consists of a graduated cylinder tube or pear-shaped bulb, which has an additional narrow-bore glass tube that begins from top of the bulb, usually has a small deformation upwards and continues to the base of the funnel, connecting with the lower tube, in the space below the stopcock and above the male ground glass joint.
The purpose of this tube is to replace the liquid volume lost in the bulb with the equivalent gas volume from the flask into which the reagent is flowing. This allows the liquid from the funnel to drop smooth without having to remove the stopper, which is necessary when needing to add exact amounts of liquid from the dropping funnel and when handling air-sensitive reagents in a sealed, inert-gas environment.
Without this tube, or some other means to equalize the pressure between a sealed receiving flask and the bulb of the funnel, the flow of fluid from the bulb will rapidly come to a halt.
Dropping funnels are useful for adding reagents slowly, i.e. drop-wise. This may be desirable when the quick addition of the reagent may result in side reactions, or if the reaction is too vigorous.
1. How to use a dropping funnel
To use the dripping funnel, you must follow the next steps:
- Check the stopcock to see if it works
- Grease the ground glass joints if the stopcock doesn’t work properly
- Pour the liquid in the funnel through the upper female joint; make sure the liquid level stays below the upper opening of the pressure-equalizing lateral glass tube
- Close the funnel using the stopper and use a keck clip if required
- Place the dropping funnel on the flask in its respective socket
- Once in place, slowly open the stopcock to release the liquid inside the funnel
- If you work in an inert atmosphere, you must do the following:
- If you’re working under inert atmosphere, you will have to replace the air inside the funnel with vacuum followed by inert gas
- To do this, attach the funnel to the flask and perform the air removal with the funnel secured to the flask
- After the funnel is filled with inert gas, take a small flask or a female of female glass stopper in one hand and be prepared to remove the dropping funnel
- Immediately as you remove the funnel from its place add the female glass plug to the bottom of the funnel and close it, move quickly to limit the amount of inert gas that leaves the funnel
- Attach the dropping funnel to the inert gas solvent distillation unit by connecting the male joint of the said installation to the top female ground glass joint and secure it using a keck clip
- Make sure the pressure equalizing tube sits in an above position to the funnel but never below, as any dripping solvent that will fill the funnel may flow in the lateral tube, ruining your setup
- When you’ve collected enough solvent, close the flow stopcock and let the solvent cool to ambient temperature
- Remove the keck clip and immediately place the stopper on the funnel then close the male joint of the installation with its female plug
- Reattach the dropping funnel to the flask, by removing the stopper from the flask, then quickly remove the female stopper of the funnel and attach the dropping funnel to the flask and securing it using a keck clip
Tips:
- If you collect a larger amount of solvent in the dropping funnel, a good idea would be to use a jackto slightly support the end of the funnel, to prevent it from snapping the male solvent dropping joint, as the funnel gets heavier and heavier
- When dropping liquid, it’s best to avoid using the stopcock hole as a reference to the dropping rate, and instead simply open the stopcock very slowly and adjust the dropping rate by using the time period between the drops
Availability
Dropping funnels are sold by lab suppliers. They are a bit pricey compared to other glassware with ground glass, as their construction is more complex.
You can also purchase them online.
2. Teflon
1. An Accidental Discovery
The Teflon™ story began on April 6, 1938. Dr. Roy J. Plunkett was working with gases related to refrigerants. After checking a frozen, compressed sample of tetrafluoroethylene, he and his associates made an unexpected discovery: The sample had polymerized spontaneously into a white, waxy solid to form polytetrafluoroethylene (PTFE).
PTFE is inert to virtually all chemicals and considered the most slippery material in existence, making it one of the most valuable, versatile technologies invented. Many industries—aerospace, communications, electronics, industrial processes, and architecture—owe some of their significant advances to PTFE.
Since its registration in 1945, the Teflon™ trademark has become a familiar brand, recognized worldwide for the superior nonstick properties associated with its use as a:
Coating on cookware
Soil and stain repellent for fabrics and textile products
Superior coating in harsh manufacturing environments and industrial products
The first Teflon™ products were sold commercially under the trademark starting in 1946. Applications and product innovations quickly followed.
Product Information
Product names may be followed by an X. Products labeled AF 1600 and AF 1600 X are equivalent, as are AF 2400 and AF 2400 X.
2. Description
Teflon™ AF is a family of amorphous fluoroplastics. These materials are similar to other amorphous polymers in optical clarity and mechanical properties, including strength. They also resemble fluoroplastics in their performance over a wide range of temperatures, outstanding electrical properties, and chemical resistance.
They are distinct from other fluoroplastics in that they are soluble in selected solvents and have high gas permeability, high compressibility, high creep resistance, and low thermal conductivity. They have the lowest dielectric constant and refractive index of any known fluoroplastic.
3. Processing
Teflon™ AF can be compression molded, injection molded, or extruded. Through these processes, various solid shapes can be formed using the product. Forms include rods, tubes, bars, and sheet of various thicknesses. In addition, Teflon™ AF can be dissolved in certain perfluorinated solvents for the production of highly uniform thin films and coatings. Methods used to produce such forms include spin, spray, and dip coating. Typical molding temperatures for Teflon™ AF 1600 range from 240 to 275 °C (464 to 527 °F); for Teflon™ AF 2400, the range is 340 to 360 °C (644 to 680 °F). The polymer begins to decompose above 360 °C (680 °F), so processing above that temperature should be avoided. Corrosion-resistant tooling is recommended, as it is for Teflon™ FEP and PFA fluoroplastic resins
4. Electrical Applications
In electronics, Teflon™ AF may be used in optoelectronic devices, where its optical clarity, temperature resistance, and dielectric properties are beneficial. It is essentially transparent to microwaves and can function as a “window” for high frequency antennas. The low dielectric constant and dissipation factor maybe advantageous in the construction of electronic devices, including special circuit boards and hybrid devices.
5. Optical Applications
Teflon™ AF can be used as a low-refractive index coating or covering for optical devices, including those that must operate over a wide temperature range and in chemically aggressive environments. Teflon™ AF offers a high level of transmission throughout the optical spectrum from infrared through ultraviolet. Some specific uses are:
- In fiber optics as a low refractive index, high temperature cladding material over silica, methacrylates, and polycarbonates.
- Its optical properties of high transmission and broad spectrum transmission make it practical as an anti-reflective coating for high energy laser applications.
- The properties of high temperature tolerance, chemical resistance, high transmission, and mechanical strength make the material ideal for use as a window. It would also be good for optical sensing and diagnostic devices.
- The low refractive index combined with its other optical properties make Teflon™ AF useful as an anti-reflective coating. It is also good as a protective coating, where optical transmission is important.
6. Mechanical Applications
Teflon™ AF exhibits excellent mechanical and physical properties at end-use temperatures up to the glass transition temperature. Teflon™ AF also demonstrates good dimensional stability, reduced mold shrinkage, a smooth surface, and rigidity at high use temperatures. These characteristics, coupled with machinability and processing versatility, make Teflon™ AF an excellent candidate for specialized chemical and industrial applications
7. Chemical Applications
As a fluoroplastic, Teflon™ AF has high resistance to chemical attack. Teflon™ AF can be fabricated into films, coatings, and smooth surfaced products, and also molded into high performance mechanical parts that can function in severe exposure conditions of high temperature, harsh chemicals, and destructive environmental agents. Teflon™ AF is an excellent candidate for the demanding and stringent conditions that exist in the electronic, chemical, military, and aerospace industries.
8. Safety Precautions
WARNING! VAPORS CAN BE LIBERATED THAT MAY BE HAZARDOUS IF INHALED. Before using Teflon™ AF, read the Safety Data Sheet and detailed information in the latest edition of the “Guide to the Safe Handling of Fluoropolymer Resins”, published by the Fluoropolymers Division of The Society of the Plastics Industry (www.fluoropolymers.org) or by PlasticsEurope (www.plasticseurope.org).
9. Handling Practices
Teflon™ AF resins may contain parts per million of residual hexafluoroacetone (HFA). Because HFA hydrates are readily absorbed through the skin, it is necessary to avoid skin contact with the resin during processing. Chemours recommends the use of protective gloves when handling resin during manufacturing operations. Residual gases (including HF, COF2, CO, and HFA) that diffuse from Teflon™ AF resins, even at room temperature, may be harmful. To avoid exposure, all resin containers should be opened and used only in well-ventilated areas using local exhaust ventilation (LEV).
3. Stopper (plug)
Unlike a lid or bottle cap, which encloses a container from the outside without displacing the inner volume, a bung is partially or wholly inserted inside the container to act as a seal. A bung can be defined as “a plug or closure used to close an opening in a drum or barrel. It is called a plug when referring to a steel drum closure.”[1]
A glass stopper is often called a “ground glass joint” (or “joint taper”), and a cork stopper is called simply a “cork”. Stoppers used for wine bottles are referred to as “corks”, even when made from another material.[citation needed]
A common every-day example of a stopper is the cork of a wine bottle. When used to seal the bungholes of barrels, the stopper is called a bung. Other bungs, particularly those used in chemical barrels, may be made of metal and be screwed into place via threading.[citation needed]
1. Ground glass joint
Ground glass joint (or ground glass stoppers) are commonly used with laboratory glassware, mainly because of their nonreactivity. Some stoppers used in labs have holes in them to allow the insertion of glass or rubber tubing. This is often used when a reaction is taking place in the flask or test tube and the byproduct or result of the reaction is desired to be collected. For instance, if one were to boil water in a test tube and wanted to collect the water vapor, one could seal the test tube with a stopper with holes in it. With tubing inserted into the hole(s), when the tube is heated, water vapor will rise through the hole, make its way through the tubing, and into the collection chamber of choice. The water vapor would not be able to escape into the air, because the stopper and the tubing, if set up correctly, would be airtight.
2. Rubber bungs
In chemistry, bungs made of hardened rubber are frequently used in small-scale experimental set-ups involving non-corrosive gases. Some chemistry bungs may also include one or more holes so a glass tube or laboratory funnel may be inserted through the bung and into the container or another piece of apparatus.
The rubber bung may be used to seal a flask because the user may require the contents to be mixed via shaking the flask or may require that the contents be kept inside the flask and prevented from leaking out. In all cases, the bung keeps the experimentation environment sealed so that liquids or gases cannot escape (or enter).[citation needed]
For applications that place higher demands on the bung in terms of temperature and mechanical stability or solvent resistance, standardized glass stoppers and connectors are preferred.[citation needed]
Bottle stoppers made from gutta-percha, a natural rubber that is both chemically resistant and thermoplastic, were the first product of the Gutta Percha Company, better known for making submarine telegraph cables.[2]
4 The Rubber Stopper: A Simple and Inexpensive Technique to Prevent Pin Tract Infection following Kirschner Wiring of Supracondylar Fractures of Humerus in Children
1. Abstract and Figures
Percutaneous pinning after closed reduction is commonly used to treat supracondylar fractures of the humerus in children. Minor pin tract infections frequently occur. The aim of this study was to prevent pin tract infections using a rubber stopper to reduce irritation of the skin against the Kirschner (K) wire following percutaneous pinning.
Between July 2011 and June 2012, seventeen children with closed supracondylar fracture of the humerus of Gartland types 2 and 3 were treated with this technique. All patients were treated with closed reduction and percutaneous pinning and followed up prospectively. Only one patient, who was a hyperactive child, developed pin tract infection due to softening of the plaster slab. We found using the rubber stopper to be a simple and inexpensive method to reduce pin tract infections following percutaneous pinning.
Question
1. What is a dropping funnel used for?
A dropping funnel or addition funnel is a type of laboratory glassware used to transfer liquids. They are fitted with a stopcock which allows the flow to be controlled. Dropping funnels are useful for adding reagents slowly, i.e. drop-wise.
2. What is the difference between a separatory funnel and a dropping funnel?
Separating funnel: Has a pear-shaped or inverted cone design with a stopcock at the bottom, allowing controlled flow of liquids. Dropping funnel: Generally a conical funnel without a stopcock, featuring a narrow neck at the bottom for channeling liquids or solids, and a wide mouth at the top for easier pouring.
3. What is the function of funnel drip in laboratory?
A Dropping Funnel is a type of laboratory glassware used for the precise dispensing of liquids in a dropwise manner. It is typically used in chemical reactions where small, accurate amounts of reagents need to be added. A Cylindrical Dropping Funnel is a type of dropping funnel that has a cylindrical shape.
4. What are 3 uses for a funnel?
Uses. To channel liquids or fine-grained substances into containers with a small opening. Used for pouring liquids or powder through a small opening and for holding the filter paper in filtration. Used in transferring liquids in small containers.
5. What is the purpose of a funnel?
A funnel is a marketing tool used to guide potential customers through the sales process. It is a visual representation of the customer journey, from initial awareness of a product or service to the final purchase.
6. What is a separatory funnel used for?
A separatory funnel, also known as a separation funnel, separating funnel, or colloquially sep funnel, is a piece of laboratory glassware used in liquid-liquid extractions to separate (partition) the components of a mixture into two immiscible solvent phases of different densities.
7. What is a pressure equalizing dropping funnel?
A pressure equalizing funnel (also known as a dropping funnel or an addition funnel) is a form of laboratory glassware used to transfer liquids. It is equipped with a stopcock (glass or PTFE) that allows the transfer to be controlled. It’s useful for gently introducing reagents, such as drop-by-drop.