• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month


Extracts from this document...


NAME : THAMARAI A/P RAJENDRAN ID NUMBER : 09ALB07214 LABORATORY 1A : ATOMIC STRUCTURE, BONDING AND PERIODICITY COURSE : BIOTECHNOLOGY (YEAR 1 SEM 1) EXPERIMENT 7: MELTING POINT OF ORGANIC COMPOUNDS. TITLE: Melting Point of Organic Compounds. OBJECTIVES OF EXPERIMENT: The objective of this experiment is to identify unknown organic compound by melting point depression method. Practice use of melting point apparatus by measuring melting point of some pure organic compound. THEORY AND BACKGROUND: The melting point of organic solid can be determined by introducing a tiny amount of the substance into a small capillary tube, attaching this to the stem of a thermometer centerd in heating bath, heating the bath slowly, and observing the temperatures at which melting begins and is complete. Pure samples usually have sharp melting points, for example 149.5�C-150�C or 189�C-190�C; impure samples of the same compounds melt at lower temperatures and over a wide range, for example; 145�C-148�C or 187�C-189�C. The contaminant that depresses the melting point and extends the melting range may be an indefinitely characterized resinous material or it may be a trace of a second chemical entity of melting point either higher or lower than that of the major component. Under equilibrium conditions (no super cooling) the temperature at which a pure solid melts is identical with that at which the molten substance solidifies or freezes. ...read more.


The most efficient procedure is to range all the samples in order of increasing melting point and determine the apparent melting point of each, beginning with the sample of lowest melting point. The apparent melting point of ice was determined by inserting the bulb of the thermometer into ice slurry. The observed melting points and corrected melting points of the standard compounds as listed earlier were recorded. A correction chart was constructed by plotting the observed melting points against the corrected melting points. The resulting points were connected, and that is the calibration curve of your thermometer. Part 2: Melting points of known compounds and mixture a) Benzoic acid b) Urea c) 10 mol per cent benzoic acid and 90 mol per cent urea d) 90 mol per cent benzoic acid and 10 mol per cent urea Part 3: Identification of an unknown compound by the mixed melting point method Six of the compounds listed below were obtained from the instructor, which will be designated by number only. Their melting points were determined and the values found were compared with those given in the table. The probable identities of the unknowns were decided and were tested in the following way: a small sample of the reference compound was secured from the shelf and its melting point was determined. ...read more.


In a sample that contains a mixture of two compounds, each component usually depresses the melting point of the other, giving an observed melting point range that is lower and broader than the melting point of either component. CONCLUSION: When a solid substance is heated, typically it will melt; that is to say, at some temperature the solid will begin to liquefy and by some slightly higher temperature all of the solid will have become liquid. The melting point (actually melting point range) of a compound is then defined as the temperature at which an observer can first see liquid forming from the solid to the temperature where the last particle of solid has become liquid. For example, the melting point of pure sucrose (table sugar) is 185o-186oC. This means that as a small sample of sucrose is slowly heated some of the crystals begin to liquefy at 185�C and all of the crystals have become liquid by 186oC. Sometimes only the second number (completely melted) is reported as the melting point. In general, this is not a good idea and should be avoided. Melting points are usually determined by placing one or two milligrams of the material to be tested into a melting point capillary, and heating the capillary and a thermometer together, and observing over what temperature range the material melts. The melting point capillary is a thin-walled glass tube, about 100 mm in length and not more than 2 mm in outside diameter, sealed at one end. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our University Degree Cell Biology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related University Degree Cell Biology essays

  1. The purpose of this investigation is to discover whether different respiratory substrates will affect ...

    The stock yeast solution must be stirred before used. I will add the sugar to the yeast as the yeast is a colloid, and I will not contaminate the solution with either sugar or yeast. * As the yeast solution sediments, I need to swerve the conical flask (containing yeast and sugar substrate)

  2. This experiment was carried out to characterize an enzyme, -amylase by extracting it from ...

    y = 0.0029x 0.011= 0.0029x Mass of ?-amylase = 3.79�g This calculation was repeated for all the test tubes in order to determine the mass of ?-amylase present. The results were tabulated in table 4. Mass of ? -amylase after 1st dialysis Since out of the total 5ml of extract

  1. POMC cell function

    is accomplished through use of the �-opiate receptor of epidermis and hair follicle melanocytes . In addition, the � - endorphin peptide alters cell dendricity (Kauser, Thody, Schallreuter, Gummer, & Tobin, 2005). The human skin mast cells express POMC protein and gene and serve as proof for the additional processing of the ?-MSH secretory molecule.

  2. Discuss how changes in control of the cell cycle contribute to cancer development ...

    Thus mitosis would be hypothesized to be an important target of genetic mutation in cancer and recent discoveries bear this out. Phenotypic defects in the centrosomes, the organising centres of the bipolar spindle, have been reported in many forms of cancer.

  1. Using Spectroscopy to Evaluate the Absorption of Light for Different Substances

    0.061 640 0.178 0.196 660 0.844 0.165 680 0.149 0.022 700 0.013 0.004 The results for the absorption of light for cholorphyll A and B are presented in Table 3. The peaks of absorption for chlorophyll A are 430nm, 615nm and 665nm.

  2. Effect of temperature on membrane permeability

    I will now need to minus the % transmission from the average. From the result I can square it to work the (x-x)�. Reading number (x-x) (x-x)� 1 74 - 73.33 = 0.67 0.67� = 0.45 2 73 - 73.33 = -0.33 -0.33� = 0.11 3 73 - 73.33 =

  1. The Use of Controls and Indicators to Find What Macromolecules are in an Unknown

    Benedict's solution is used to indicate the presence of an aldehyde or ketone functional group. An aldehyde functional group is found in a reducing sugar when in a basic solution. A reducing sugar is a sugar that has a potentially free aldehyde group that is used for reducing alkaline solutions.

  2. Discuss the possible role of dopamine in incentive salience? How might this lead to ...

    Therefore in a patient suffering with schizophrenia, each and every stimulus would have its own personal significance and meaning. Dopamine neurons such as midbrain dopamine neurons of the ventral tegmental area and substantia nigra pars compacta send projections to striatum and prefrontal cortex.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work