Instruments that are used in lab, their uses and mechanism
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Condensers are used to cool hot vapors and condense them into liquids. They are commonly used in reflux and distillation processes. A condenser consists of an inner glass tube surrounded by an outer tube through which coolant flows. Suction pumps use atmospheric pressure and valves to draw liquid up through the pump. They are often used to accelerate filtration processes. Buchner funnels speed up solid/liquid separation using vacuum filtration. The liquid is drawn through a perforated plate, leaving the solid component on a filter paper. They are mainly used to dry crystals after recrystallization.
![Instruments that are used in lab, their uses and mechanism
P a g e 15 | 20
Used to test for basicity:
Red litmus paper consists of cellulose paper infused with dye molecules that
have already been degraded by acid (hence the red colour). Red litmus paper
essentially functions as blue litmus paper in reverse.
As a solution's pH increases, the concentration of hydrogen ions decreases but
the concentration of hydroxide ions [OH-] increases. These negatively-charge
ions "steal" hydrogen atoms from the degraded dye molecules to form water.
The dye molecule respond to the lost hydrogen by forming double bonds
between their carbon and oxygen atoms.Inthis way, thedyemolecule "rebuild"
their electron networks and regain their original blue colour.
8) Pipette:Itisa smallpieceof apparatuswhichtypically consistsofa narrow
tube into which fluid is drawn by suction (as for dispensing or
measurement) and retained by closing the upper end.](https://image.slidesharecdn.com/medicinallabassignment-160331154816/85/Instruments-that-are-used-in-lab-their-uses-and-mechanism-15-320.jpg)
Instruments that are used in lab, their uses and mechanism
- 1. Instruments that are used in lab, their uses and mechanism P a g e 1 | 20 1) Condenser: Condenser is an apparatus or container for condensing vapour. It is an apparatus for reducing gases to their liquid or solid form by the abstraction of heat.
- 2. Instruments that are used in lab, their uses and mechanism P a g e 2 | 20 Uses of condenser: i. Condensers are often used in reflux, where the hot solvent vapours of a liquid being heated are cooled and allowed to drip back. This reduces the loss of solvent allowing the mixture to be heated for extended periods. ii. Condensers are used in distillation to cool the hot vapours, condensing them into liquid for separate collection. For fractional distillation, an air or Vigreux condenser is usually used to slow the rate at which the hot vapours rise, giving a better separation between the different components in the distillate. iii. Mainly condensers are used in the medicinal chemistry lab in order to reduce drug loss. Mechanism of condenser: A condenser is a piece of laboratory glasswareused to cool hot vapours or liquids. A condenserusually consistsof a large tube containing a smaller glass tube running its entire length, within which the hot fluids pass. The ends of the inner glass tube are usually fitted with ground glass joints, which are easily fitted with other glassware. During reflux, the upper end is usually left open to the atmosphere or vented through a bubbler or a drying tube to prevent the ingress of water or oxygen. The outer glass tube usually has two hose connections, and a coolant (usually tap water or chilled water/anti- freezemixture) is passedthroughit. Formaximumefficiency, and to maintain a smooth and correctly directed thermal gradient so as to minimise the risk of thermal shock to adjacent glassware, the coolant usually enters through the lower fitting, and exits through the higher fitting. Maintaining a correct thermal gradient (i.e. entering coolant at the cooler point) is the critical factor.
- 3. Instruments that are used in lab, their uses and mechanism P a g e 3 | 20 2) Suctionpump: Itis a pump forraisingsolventbysuction process.Itusually consist of a cylinder containing a piston fitted with a flap valve.
- 4. Instruments that are used in lab, their uses and mechanism P a g e 4 | 20 It is a common pump in which the liquid to be raised is pushed by atmospheric pressure into the partial vacuum under a retreating valved piston on the upstrokeand reflux is prevented by a valve in the pipe that permits flow in only one direction. Uses of Suction Pump: i. Itactually used to accelerate the filtration. Mechanism: Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area. A suction pump works by atmospheric pressure; when the piston is raised, creating a partial vacuum, atmospheric pressure outside forces water into the cylinder, whence it is permitted to escape by an outlet valve. It actually used to accelerate the filtration. Pumps typically have an inlet wherethe fluid enters the pump and an outlet where the fluid comes out. The inlet location is said to be at the suction sideof the pump. The outlet location is said to beat the dischargesideof the pump. Operation of the pump creates suction (a lower pressure) at the suction side so that fluid can enter the pump through the inlet. Pump operation also causes higher pressure at the discharge side by forcing the fluid out at the outlet. There may be pressure sensing devices at the pump's suction and/or dischargesides which controlthe operation of the pump. For example, if the suction pressureof a centrifugal pump is too low, a device may trigger the pump to shut off to keep it from running dry with no fluid entering.
- 5. Instruments that are used in lab, their uses and mechanism P a g e 5 | 20 3) Buchner funnel: Itis a cylindrical often porcelain filtering funnel that has a perforated plate on which the filter paper is placed and that is used usually with a vacuum. It is named after its inventor, Eduard Buchner (1860–1917), German chemist.
- 6. Instruments that are used in lab, their uses and mechanism P a g e 6 | 20 Uses of Buchner funnel: i. The main use is to dry crystals after recrystallization. ii. The Buchner funnel simply speeds up the separation of solid/liquid mixtures bydrawingoff theliquid under vacuumand catching thesolid component on a piece of filter paper. This basic concept can save significant amounts of time compared to the much slower process of gravity filtration. iii. The main advantage in using this type of filtration is that it proceeds much more quickly (severalorders of magnitude) than simply allowing the solventto drain through the filter medium via the force of gravity. Mechanism: A Buchner funnel is a piece of laboratory equipment used in filtration. It is traditionally made of porcelain, but glass and plastic funnels are also available. On top of the funnel-shaped part there is a cylinder with a fritted glass disc/perforated plate separating it from the funnel. A funnel with a fritted glass disc can be used immediately. For a funnel with a perforated plate, filtration material in the formof filter paper is placed on the plate, and the filter paper is moistened with a solvent to prevent initial leakage. The liquid to be filtered is poured into the cylinder and drawn through the perforated plate/fritted glass disc by vacuum suction. The suction allows the wet recrystallized compound to dry out such that the pure dried crystal compound is left remaining. However, it is often the case that further drying is required, by an oven or other means, in order to remove as much residual solvent as possible.
- 7. Instruments that are used in lab, their uses and mechanism P a g e 7 | 20 4) Beaker: Itis a deep wide mouthed thin-walled vesselusually with a lip for pouring that is used especially in science laboratories.
- 8. Instruments that are used in lab, their uses and mechanism P a g e 8 | 20 Uses of Beaker: i. Used as a laboratory container and mixing jar. ii. Used especially in chemistry for holding and measuring liquids. iii. Container for stirring, mixing and heating liquids.
- 9. Instruments that are used in lab, their uses and mechanism P a g e 9 | 20 5) Measuring cylinder: It is a narrow, cylindrical container marked with horizontallines to represent units of measurement and used to precisely measure the volume of liquids.
- 10. Instruments that are used in lab, their uses and mechanism P a g e 10 | 20 Uses of Measuring cylinder: i. A measuring cylinder is used in a laboratory for measuring exact quantities of a liquid. ii. Inthe chemistry laboratory,themeasuring cylinder is used in titration, a procedure used to determine the concentration of a chemical in a solution. iii. Because scientists use them to measure small and large volumes, measuring cylinders come in different sizes. iv. The can be used to calculate the density of an object if it’s mass is known. v. Measuring cylinders are generally more accurate and precise than laboratory flasks and beakers. Mechanism: Itis important to choose the correctmeasuring cylinder for the volume that is wishto measure.Itis also importantto takea carefullook atthe graduation scaleon the measuringcylinder beforeusing it. Ithaveto make surethat one know which volume is represented by the distance between two adjacent graduation marks. Always leave the measuring cylinder on a flat surface when one is reading the volume of the liquid it contains. One should move one’s body downwards so thatyour eyeis on the same horizontalline as the surfaceof the liquid. One should not lift the measuring cylinder to measure the volume of the liquid contained in it.
- 11. Instruments that are used in lab, their uses and mechanism P a g e 11 | 20 6) Conical flask: It is a flask having a wide base, narrow neck and conical form, convenient in laboratory experimentation for various purpose.
- 12. Instruments that are used in lab, their uses and mechanism P a g e 12 | 20 Uses of Conical flask: i. Used to heat and store substances. ii. Used to swirlingliquids by handwithout therisk of spilling and reduces the loss of the evaporation (because of the narrow neck). iii. Used to manipulate solutions or to carry out titrations. iv. Hot vapours condense on the upper section of the Erlenmeyer flask, reducing solvent loss. v. Its narrow necks can also support filter funnels. Mechanism: In a titration experiments you place the conical flash below the burette and release the acid into the flask which contains a base and you shakethe flask to mix throughout the experiment. Titration experiments are used to find out the amount of acid required to neutralise the base, and ultimately the concentration of the base.
- 13. Instruments that are used in lab, their uses and mechanism P a g e 13 | 20 7) Litmus paper: Filter paper which has been treated with a natural water- soluble dye obtained from lichens. The resulting piece of paper, called 'litmus paper'. It is a strip of paper impregnated with litmus used as a chemical (colour) indicator.
- 14. Instruments that are used in lab, their uses and mechanism P a g e 14 | 20 Uses of Litmus paper: i. Used as a pH indicator. Blue litmus paper turns red under acidic conditions (pH below 4.5) while red litmus paper turns blue under alkaline conditions (pH above 8.3). Neutral litmus paper is purplish in colour. ii. Wet litmus paper can also be used to test water-soluble gases; the gas dissolvesin the water and the resulting solution coloursthe litmus paper. For instance, ammonia gas, which is alkaline, colours the red litmus paper blue. iii. Chemical reactions other than acid-base reaction can also cause a colour change to litmus paper. For instance, chlorine gas turns blue litmus paper white – the litmus dyeis bleached,due to presenceof hypochlorite ions. This reaction is irreversible, so the litmus is not acting as an indicator in this situation. Mechanism: Used to test for acidity: Blue litmus paper consists of cellulose filter paper infused with a solution of litmus dye freshly extracted from lichens. In an alkaline solution, the hydrogen ion levels are too low to significantly damagethe chromophore'sdoublebonds,preservingthenaturalblue colour.In a neutral solution like distilled water, the hydrogen ion levels are significant enough to begin damaging a significant number of dye molecules. For those molecules that are affected, the hydrogen-degraded chromophores cause the dye molecules to turn from blue to red. At the microscopic level, the litmus paper is a mixtureof unaffected blue molecules and degraded red molecules. To the observer, however, the paper appeared to be a uniform shade of purple. Finally, in an acidic solution, the excess of hydrogenions manage to degrade the vast majority of chromophore double bonds, turning the litmus paper entirely red.
- 15. Instruments that are used in lab, their uses and mechanism P a g e 15 | 20 Used to test for basicity: Red litmus paper consists of cellulose paper infused with dye molecules that have already been degraded by acid (hence the red colour). Red litmus paper essentially functions as blue litmus paper in reverse. As a solution's pH increases, the concentration of hydrogen ions decreases but the concentration of hydroxide ions [OH-] increases. These negatively-charge ions "steal" hydrogen atoms from the degraded dye molecules to form water. The dye molecule respond to the lost hydrogen by forming double bonds between their carbon and oxygen atoms.Inthis way, thedyemolecule "rebuild" their electron networks and regain their original blue colour. 8) Pipette:Itisa smallpieceof apparatuswhichtypically consistsofa narrow tube into which fluid is drawn by suction (as for dispensing or measurement) and retained by closing the upper end.
- 16. Instruments that are used in lab, their uses and mechanism P a g e 16 | 20 Uses of Pipette: i. Used to measure or transfer a quantity of a liquid. Mechanism: In a way, pipettes work a lot like drinking straws in that they allow liquids to be 'sucked-up'into one end. Though they may work like drinking straws, never use yourmouth to suck-upliquidsinto a pipette! Insteadusea pipette-aide. Pipette- aides or pipettors aresuction devices that are used to either suck liquids into or expel liquids out of pipettes. For some types of measurements it may be necessary to expel, or blow-out, the total liquid volume from the pipette using the pipette-aid. A pipette is calibrated with a series of graduation lines to allow the measurement of more than one volume. Measure using the bottom of the concave surface of the liquid in pipette. Most of our work is done with sterile pipettes and if so, theoperations aredoneaseptically. When workingwith non- sterile pipettes it is a good idea to workaseptically anywayasa matter of routine in order to practice the technique. 1. Without opening the sterile sleeve, look through the wrapper and check that the pipette is calibrated as a 'blow-out'pipette. Also make surethat the tip is not crackedor chipped and check the wrapperhasn'tbeen damaged in any way. 2. Open the wrapper and remove the pipette aseptically and insert the top, wide end into a pipette-aide. 3. Fill the pipette a bit abovethe capacity line desired and then slowlylower the meniscus to that capacity line. 4. Remove the pipette from the vessel, allowing the outside of the pipette to gently touch the inner lip of the vesselto removeany adherent liquid. Don't touch the tip of the pipette though to avoid introducing an air bubble. 5. Aseptically move the pipette to the receiving vessel and deliver the contents. If you are pipetting a volume between two measurement lines you will not have to 'blow-out'. However if you are delivering the entire contents of the pipette you will haveto 'blow-out'the remaining liquid in the tip with a firm puff of air from the pipette-aide. 6. Remove the pipette aseptically and discard it into an appropriate discard container.
- 17. Instruments that are used in lab, their uses and mechanism P a g e 17 | 20 9) Test tube: A cylindrical tube of clear glass, usually open at one end and rounded at the other, used as a container for small amounts of a substance in laboratory tests and experiments.
- 18. Instruments that are used in lab, their uses and mechanism P a g e 18 | 20 Uses of Test tube with mechanism: i. Test tubes are used by chemists in the lab to heat, hold and mix small quantities of liquid or solid chemicals during experiments. ii. Test tubes haveclear glass to allow monitoring and observationduring an experiment. iii. A test tube with a stopper is used to store samples and for other storage purposes. iv. The test tube is made of specialized glass so it can be heated and cooled without breaking. v. Their round bottom and straight sides minimize mass loss when pouring, make them easier to clean, and allow convenient monitoring of the contents. vi. The long, narrow neck slows down thespreading of vapours and gases to the environment. vii. A test tube filled with water and upturned into a water-filled beaker is often used to capture gases, e.g. in electrolysis demonstrations.
- 19. Instruments that are used in lab, their uses and mechanism P a g e 19 | 20 10) Round bottom flask: A glass flask used in a laboratory for holding chemical liquids and solutions, which has a spherical shape for uniform heating, and one or more long cylindrical necks.
- 20. Instruments that are used in lab, their uses and mechanism P a g e 20 | 20 Uses of Round bottom flask: i. Round-bottom flasks are used to contain chemical reactions run by chemists, especially for reflux set-ups and laboratory-scale synthesis. ii. The round-bottom flask is used for reactions, distillations and collection. iii. It is used for uniform heating and boiling of liquid. Mechanism: Round-bottom flasks are types of flasks having spherical bottoms used as laboratory glassware, mostly for chemical or biochemical work. They are typically made of glass for chemical inertness and in modern days, they are usuallymade of heat-resistantborosilicateglass.Thereis atleast one tubular section known as the neck with an opening at the tip. Two or three-necked flasks are common as well. Round bottom flasks come in many sizes, from5 mL to 20 L, with the sizesusuallyinscribed on the glass. Becauseof the round bottom, cork rings are needed to keep the round bottom flasks upright. When in use, round-bottomflasks arecommonly held at the neck by clamps on a stand.