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Basic Techniques in Practical Chemistry

"These videos contain valid information that is useful to AP (Advanced Placement) students."
- Richard Erdman, AP Chemistry Teacher, Venice High School, California

Explore this Exciting New 10 Volume Series.

Volume 1: Determination of Melting Point
The introduction explains the significance of melting point (m.p.) and m.p. range, the effect of impurities, and use of m.p. as a means of assessing purity. Techniques are demonstrated for preparing a sample for m.p. determination (preparing a capillary tube, preparing the sample and loading the tube), and using an electric m.p. apparatus for both "rough" and accurate determinations. The importance of keeping detailed records is emphasised, and the criteria for assessing results are described. The mixed melting point method for confirming the identity of an unknown sample is explained and demonstrated. The microscope melting point apparatus is demonstrated and its advantages discussed.  Duration: 29 minutes
Volume 2: Recrystallization Part 1
The aims and principles of recrystallisation and use of melting point as a criterion for assessing results are summarized. Determination of suitable solvents for recrystallisation by testing sample solubility in hot and cold aqueous and non aqueous solvents is demonstrated, emphasising the importance of maintaining systematic laboratory notebook records. Techniques demonstrated include weighing out the sample using a "rough" digital balance, sample dissolution, cooling the solution, and recovery of the recrystallised sample by Buckner filtration at the water vacuum pump. Strategies to maximise recovery are summarized.  Duration: 38 minutes
Volume 3: Recrystallization Part 2
Building on programme 2, this programme focuses on the use of decolourising charcoal and filtration of hot solutions during recrystallisation. The need for, and use of decolourising charcoal are described, including the safe procedure for addition to the hot solution. Preparation of a gravity filtration apparatus with both normally folded and fluted filter papers is described in detail.Hot filtration procedures demonstrated are: gravity method with pre heated funnel, gravity method for low boiling non aqueous solvents, Buchner method with pre heated funnel, and large and small scale gravity methods using steam heated funnels.  Duration: 24 minutes
Volume 4: Distillation
The brief introduction summarizes the purpose and principle of distillation at atmospheric pressure. Full details of distillation apparatus assembly are demonstrated, providing the student, at the same time, with a thorough basis for constructing many other types of apparatus used in synthetic organic chemistry. The techniques include: use of clamp stand laboratory jack, heating mantle, assembly and support of apparatus with ground glass joints, setting up a water jacket condenser and thermometer pocket. Criteria for choosing the size of apparatus and alternative heating methods (mantle, Bunsen burner, water bath, oil bath) are discussed.The progress of a distillation is followed and a method for monitoring and recording is suggested.  Duration: 33 minutes
Volume 5: Infrared Spectroscopy
Use of infrared (ir) spectroscopy to provide structural information quickly is summarized. The demonstration of sample preparation covers handling, cleaning and storage of potassium bromide plates, preparation of a liquid sample as a capillary film, and preparation of a solid sample as a Nuiol mull. The general method of operating a simple routine infrared spectrophotometer is described (using a Perkin Elmer PE1310).  Positioning the sample, setting chart expansion, scan time, and starting % transmittance (including use of a reference beam attenuator) are covered. Criteria for assessing quality of spectra are detailed and remedial action suggested for unsatisfactory spectra.  Duration: 38 minutes
Volume 6: Weighing Samples For Analysis
This programme describes a method for weighing out analytical samples for difference, quickly and efficiently using modern electronic balances. The care to be given to analytical balances is demonstrated and emphasised by a look at the precision engineering inside a balance. Use of a weighing bottle and the "tare" facility on balances is described.  Duration: 20 minutes
Volume 7: Volumetric Techniques
By demonstration of the fine details of handling volumetric apparatus, this programme lays the foundation for the meticulous and systematic techniques needed for successful volumetric analysis. Demonstration of cleaning and care of volumetric glassware (burette, pipette, and volumetric flask) covers recognition of dirty glassware, effects on results, and use of detergent solutions.Making up analytical solutions by dissolving solids, particularly in volumetric flasks, is described. Use of the pipette is demonstrated, including loading using a pipette bulb or syringe filler, rinsing, filling to the mark, and delivery of an accurate volume. Methods for using burettes are detailed including clamping the burette, rinsing and filling, reading and burette control techniques during titration.  A concise method for recording results is suggested.  Duration: 51 minutes
Volume 8: Hydrolysis Of An Ester
Using the base catalysed hydrolysis of phenyl benzoate as an example, this programme builds on Programme 4 to illustrate further simple apparatus for synthetic and work up procedures in organic chemistry. Assembly and operation of apparatus for reflux are demonstrated, including use of anti bump granules and heating control. The method for changing solution pH is illustrated using sodium carbonate and monitoring with Universal indicator paper. Solvent extraction techniques, including summary of the principle, use of separating funnels, and safety precautions, are described using extraction of the hydrolysis product, phenol, for aqueous solution into diethyl ether. Drying a solid product using a desiccator containing self indicating desiccant (silica gel) is illustrated.  Duration: 34 minutes
Volume 9: Thin Layer Chromatography
The principle, practice, and safety aspects of thin layer chromatography (tlc) are shown using the separation of a mixture of phenol and hydroquinone as an example. The demonstration covers preparation of micropipettes for "spotting" plates, preparation of sample solutions, marking up and "spotting" tlc plates, and preparation and use of a simple tlc tank. Locating spot positions using an ultra violet lamp (non-destructive) and an iodine tank (destructive) are described, and the determination and significance of Rr values are discussed.  Duration: 43 minutes
Volume 10: Gravimetric Techniques
This programme details the techniques and skills of gravimetric analysis using, as an example, the determination of nickel as nickel dimethylglyoximate. The choice, preparation, and handling of sintered glass crucibles is described. Details of the heating/cooling/weighing cycle involved in drying to constant weight are provided. Filtration is achieved using a Buchner apparatus at the water vacuum pump. Apparatus assembly, and detailed techniques for precipitate transfer and washing, are demonstrated.  Duration: 25 minutes
Basic Techniques in
Practical Chemistry
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