🔎 Dean Stark’s apparatus: definition and explanations


Diagram of a Dean-Stark

L’Dean-Stark applianceWhere is it Dean StarkWhere is it Dean and Stark applianceis a montage of laboratory glassware (Laboratory glassware refers to various vessels, tools and equipment made of …) used in chemistry (Chemistry is a natural science divided into several specialties, a …) synthesis to extract water (or other liquids) from a reaction medium. It was invented by EW Dean and DD Stark in 1920.

It is used in conjunction with a coolant water (Water is an omnipresent chemical compound on Earth, essential for everyone …) and a thermo mantle to remove the water produced by a chemical reaction (A chemical reaction is a transformation of matter during which …) which takes place in heater (Heating is the action of transmitting thermal energy to an object, to …) at ebb.

There are two types of Dean and Stark devices, depending on whether the density (The density or relative density of a body is the ratio of its density to the …) from solvent (A solvent (also called thinner for strong solvents in French-speaking Switzerland) is a …) used is lower or higher than that of water.

A Dean-Stark in the laboratory usually consists of a cylindrical piece of glassware and vertical (The (rare) vertical, or vertical, style is a style of musical writing consisting of …)being generally graduated as a whole length (The length of an object is the distance between its two furthest ends …) and to finish with a touch, everything (The all-encompassing as the whole of what exists is often interpreted as the world or …) like an ampoule. The top of cylinder (A cylinder is a surface in space defined by a line (d), called …) it is mounted on the bottom of the reflux condenser, but it also has an arm which is mounted on the flask or reactor (A reactor may refer to 🙂 containing the reaction medium.

During the reaction, the vapors containing the solvent and the species to be extracted rise to the condenser and, once liquefied, fall into the graduated cylinder. Inside, immiscible liquids separate into phases. When the phase (The word phase can have different meanings, it is used in different fields and …) upper (less dense) reaches the level of the arm, flows there and returns to the reactor flask, while the lower phase remains in the cylinder. When this lower phase also reaches the arm, it could also return to the reactor, so it must be emptied (by opening the tap) as required.
This device is generally used for distillation (Distillation is a process of separating a mixture of liquid substances …) azeotropic. For example, to remove the water produced by a reaction involving the toluene (Toluene, also called methylbenzene or phenylmethane is …). A mixed (A mixture is an association of two or more solid, liquid or gaseous substances …) heteroazeotrope of toluene and water evaporates from the flask, but only the toluene returns (being of lower density) since it floats above the water that accumulates in the “burette”.
The Dean and Stark method is often used to measure the moisture content of products such as bread in the food industry.

However, this device can be used for purposes other than the simple elimination of water. For example in the case of the esterification of butanol with acetic acid catalyzed by sulfuric acid. The vapors contain 63% ester, 24% water and 8% alcohol and the phase organic (Organic chemistry is a branch of chemistry that deals with the description and study of a great …) harvest contains 86% ester, 11% alcohol and 2% water which is reintroduced into the medium. The aqueous phase is 97% pure.

Another example is the esterification of benzoic acid with butanol, where the ester produced is isolated in the burette, while the butanol, immiscible with the ester, returns to the reaction medium.
The removal of water during these esterification reactions shifts the chemical equilibrium in favor of the formation of esters.

Legend of the diagram

1: Magnetic bar for thefeverish activity (Agitation is the operation that consists in mixing one or more phases …) or pumice stones

2: Ball round (The word tondo characterizes and for abuse of language designates a circle or a sphere. In …) with a ground neck containing the reaction medium

3: Vigreux column

4: Thermometer (A thermometer is a device used to measure and display the value of …) graduate

5: straight capacitor

6: Cooling water inlet

7: Cooling water outlet

8: Ampoule

9: Faucet

10: Container for collecting the distillate


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