Description of a Standard 125 ml Separatory Funnel

Transcription

1 Description of a Standard 125 ml Separatory Funnel 1.0 GENERAL DESCRIPTION Separatory funnels are laboratory glassware used in the realm of organic chemistry for liquidliquid extractions which involves separating a liquid solvent from a liquid mixture. They can come in a large variety of sizes, but 125 ml is the standard within research laboratories. Separatory funnels are often designed to hold very large volumes within industrial environments where mass production is necessary. Chemists frequently use separatory funnels on their own or as a component in a larger setup such as a direct steam distillation apparatus. The following outlines the common uses of a separatory funnel and all of its parts. 1.1 Purpose and Use of a Separatory Funnel A separatory funnel is primarily used in the separation of a mixture into two immiscible solvents like oil and water. Most often, this is conducted using the Acid-Base Extraction Theory. That is, through a series of acid or base washes that neutralize the solution and leave behind the organic material. During extraction, two visible layers form within the separatory funnel: (1) the polar, aqueous layer and (2) the non-polar, organic layer. The denser of these two layers will always be the bottom layer and then drained through the bottom of the separatory funnel. The less dense layer will remain within the separatory funnel and continue to undergo washes until extraction is complete. The result is two separate products that were once combined in a mixture. 1.2 Parts Breakdown Figure 1: A standard 125 ml separatory funnel from C & A Scientific: Separatory Funnel with PTFE stop. The components of a separatory funnel include: the body, the stopper, and the stopcock. The stopcock, however, is made up of four parts within itself: a Teflon valve, a Teflon washer, a black O-ring, and a Teflon nut. The separatory funnel body has the ability to be sealed from the outside by both the stopper and the stopcock at the top and bottom, respectively.

2 Figure 2: Parts of the Separatory Funnel. 2.0 FUNCTIONAL DESCRIPTIONS OF PARTS The separatory funnel is made from borosilicate glass, a minimal amount of rubber, and polytetrafluoroethylene (PTFE) which is more commonly known as Teflon. Each part is described in further detail below. 2.1 Separatory Funnel Body The borosilicate glass body accounts for a vast majority of the separatory funnel. Mostly conical in shape, the body functions as the storage vessel which has a capacity of 125 ml. Its dimensions are approximately 22 cm in height and 7 cm in diameter at its widest. William Sabel, industrial chemistry lecturer at Oxford, affirms that the use of borosilicate glass is most commonly used in

3 the laboratory setting for two important reasons: (1) it can withstand uneven heating and (2) it is unlikely to chemically react with the contents it holds (13). Thus, the separatory funnel body is highly resilient to breaking, cracking, or melting and will not interfere with the chemical mixtures it is responsible for holding. 2.2 Stopper The stopper s purpose is to contain the liquid within the body while inverting the funnel, a frequent occurrence in the extraction process. Like the separatory funnel body, it is made from borosilicate glass. For convenience and ease of gripping, it is close to the size and shape of a thumb. It is approximately 4 cm in length and 2 cm in diameter. 2.3 Stopcock There are two primary functions of the stopcock: (1) to hold or release liquid from the separatory funnel body and (2) to release pressure build up inside the funnel while inverting. Both of these functions are done by opening or closing the valve. The stopcock is composed of 4 parts as illustrated in Figure 2: Teflon Valve: The primary component of the stopcock is the blue Teflon valve. The valve is used to control the flow of liquid out the bottom of the funnel. In both Figures 1 and 2 the valve is shown to be in the open position. That is, perpendicular to the counter; if the valve were parallel to the counter it would be closed. The valve can be adjusted at various degrees to control the flow rate. Its triangular shape is inserted into the separatory funnel body with a handle remaining on the outside. It is approximately 4.5 cm wide with a handle 4 cm long. Like borosilicate glass, Teflon is chemically inactive and is therefore a commonly used material in stopcocks. Teflon Nut: Also made of Teflon, the nut is the external most part of the nut and washer system. The nut and washer system is used to secure the valve in place. It is a standard plastic nut approximately 1 cm thick. Black O-ring: Working in conjunction with the nut and washer, the black rubber O- ring is situated between the two. The main purpose of the O-ring is to prevent leakage. It is approximately 2 mm thick. Teflon Washer: To complete the system, the Teflon washer is sandwiched between the O-ring and the valve. Its purpose is to ensure the nut tightens on to a smooth surface and will therefore not loosen over time. It is a standard plastic washer approximately 3 mm thick.

4 3.0 BENEFITS OF A SEPARATORY FUNNEL Together, the separatory funnel body, stopper, and stopcock construct this basic apparatus used for a variety of purposes. Most significantly, it is used in laboratories everywhere in order to isolate or purify a product. It is a common piece of laboratory equipment within pharmaceutical companies used in the research and production of potential drugs. 3.1 Teflon Stopcock Benefits Specific to this product, the Teflon stopcock is highly favored over glass stopcocks. Teflon is beneficial because it is chemically inactive, as aforementioned, and it requires no grease or lubrication. Glass stopcocks often require oil that is chemically active resulting in experimental errors. Therefore, this product s use of Teflon and as previously discussed, borosilicate glass, significantly limit the possibilities of error and make this product extremely useful.

5 Works Cited Sabel, William. Basic Techniques of Preparative Organic Chemistry. Oxford: Pergamon Press Ltd., Print. Separatory Funnel with PTFE Stop. Photograph. C & A Scientific. C & A Scientific Co., Inc., n.d. Web. 24 Feb