Category: Lab report

Projectile Motion (Lab Report)

Question: What is the relationship between horizontal velocity and horizontal distance for a projectile?

Objective: To investigate the relationship between horizontal velocity and horizontal distance for a projectile.

  • Introduction/theory
  • Method
  • Data
  • Conclusion
  • Double spaced, 12 font, MLA format

Extraction of Caffeine from Coffee and Chocolate Bars (Lab Report)

Materials/Equipment:

2 oz. each of 43%, 70%, and 100% chocolate bars

Petroleum Ether                                                          Freezer

Mortar & pestle                                                           Electronic analytical balance

15 mL centrifuge tubes                                               50 & 250 mL Erlenmeyer flasks

Centrifuge                                                                   Dropper

Deionized water                                                          Conical funnel

Water Bath                                                                  Gilson PIPETMAN P20 pipette

1000 mL beaker                                                          0.45 mm filter paper

Hot plate                                                                     Caffeine stock, powdered

Chromatography C18 column packed with silica (SiO2)

Thermo Scientific UHPLC coupled to TSQ Quantum Vantage triple-stage quadrupole mass spectrometer (Thermo Fisher Scientific, San Jose, CA).

Cold Bruer Drip Coffee Maker                                  Folgers Classic Roast Instant Coffee

Mr. Coffee Single Serve Coffee Maker                      Folgers Regular Classic Roast Ground Coffee

 

Procedure

Caffeine Extraction and Quantitation from Chocolate

  1. Obtain 2 oz portion of chocolate and slice into small pieces.  Place sliced chocolate into mortar and place in freezer along with pestle until cold.2.  Obtain and weigh a 15 mL centrifuge tube on an electronic balance.  Record weight then add frozen chocolate to tube.

    3.  Add 10mL petroleum ether to tube then close cap.  Shake tube vigorously for 30 seconds in order to dissolve fat from the chocolate into the solvent.

    4.  Place tube in centrifuge and spin for 1 minute at 8,000 rpm.  Decant supernatant.  Repeat Steps 3 & 4 two more times to ensure fat is completely removed from the chocolate.

    5.  Add 500 mL of water to a 1000 mL beaker and bring to a boil using a hot plate.  Place tube with chocolate in boiling water for 10 minutes in order to remove any residual solvent in the chocolate.

    6.  Calculate the mass of the chocolate residue by weighing tube with chocolate residue and subtracting the weight of the empty centrifuge tube recorded in Step 2.  Record result.

    7.  Add 3 mL of deionized water to tube with chocolate. Heat tube by placing in boiling water to soften chocolate.  Begin stirring contents to suspend as much chocolate as possible.

    8.  Obtain and weigh a 50 mL Erlenmeyer flask.  Record weight.

    9.  Pour suspension into a 50 mL Erlenmeyer flask.  Repeat Steps 7 & 8 until all chocolate from centrifuge tube has been transferred to the flask.

    10.  Add deionized water to flask to bring the volume to 30 mL.  Place flask into a boiling water bath for X minutes to extract all the caffeine from the chocolate into the water.

    11. Place the flask onto an electronic balance.  Using a dropper filled with deionized water, add water drop by drop until the weight of water equals 33.3 g.

    12.  To remove all chocolate particles from the solution, aliquot contents into centrifuge tubes and centrifuge for 1 minute at 8,000 rpm.

    13.  Place conical funnel lined with 0.45 mm filter paper into a clean flask.  Filter suspensions from centrifuge tubes by pouring contents into funnel.

    14.  Repeat Steps 12 & 13 five more times to obtain a clean sample.

  2. Prepare the following standards by dissolving powdered caffeine stock into hot water:
    – 0.5 mg/mL concentration = 5 mg caffeine into 10 mL deionized water
    – 1.0 mg/mL concentration = 10 mg caffeine into 10 mL deionized water
    – 1.5 mg/mL concentration = 15 mg caffeine into 10 mL deionized water

–  2.0 mg/mL concentration = 20 mg caffeine into 10 mL deionized water

16.   Inject 20 ml of 0.1 mg/mL standard into HPLC for analysis.  Repeat for each standard to construct calibration curve.

17.  Inject 20 ml of sample into HPLC for analysis.

18.  Repeat process for each type of chocolate to be analyzed, with the exception of Steps 15 & 16 as calibration curve will be used for all chocolate samples.

  1. Using chromatogram results, quantitate the amount of caffeine per each 2 oz. serving of chocolate in mg

Caffeine Extraction and Quantitation from Coffee

  1. Prepare each sample by using 5 g of coffee with 8 oz water. Using regular ground coffee, follow manufacturer’s instructions for drip and brewed coffee makers. For instant coffee, simply dissolve instant coffee grinds into hot water and stir.
  2. Filter drip coffee sample using a filter funnel lined with 0.45 um filter paper into a clean 250 mL Erlenmeyer flask.
  3. Inject 20 ml of sample into HPLC for analysis.
  4. Repeat Steps 2 & 3 for brewed and instant coffee samples.
  5. Using chromatogram results, quantitate the amount of caffeine per each 8 oz. serving of coffee in mg

Packed Column Experiment (Lab Report)

Packed Column

PRESSURE DROP AND FLOODING

The packed column is used in industry to produce mass transfer, i.e. gas absorption, distillation, and liquid extraction.  This experiment is intended to study the factors affecting the capacity of a packed column to handle liquid and gas flows.  The flow will be counter-current:  gas will move upwards and liquid will move downwards.

As the flow rate of liquid or gas is increased through a packed column of constant diameter, the pressure drop per foot of packing increases.  If there is no liquid, so that the column is dry, we have a case of gas flowing through a packed bed.  In that case we might expect the Ergun equation (Treybal1, p. 200) to apply.  If liquid is flowing counter-current to the gas, each phase will take some of the room in the column, so each will have an effect on the pressure drop.  We can get some idea of the accuracy of an empirical correlation in the literature by comparing measured pressure drops with values predicted by the correlation for the same conditions.

To have flow of gas upwards through the column, the pressure must be higher at the bottom of the column than at the top.  The liquid flows downward through the packing against the pressure and the flowing gas phase because the liquid is appreciably denser than the gas and so is pulled down by gravity.  The pressure gradient in the column opposes the flow of liquid.  If we keep the flow rate of either liquid or gas constant and increase the flow rate of the other phase, we will eventually come to a limiting condition in which counter-current flow cannot be maintained.  This limiting condition is called flooding.

In practice, the diameter of a packed column is designed for a certain approach to flooding.  The diameter of the column is calculated so that the design gas rate is usually 50 to 70 percent of the flooding rate.  This percentage approach is determined by economics and by the uncertainty of predicting the flooding point.  Decreasing the column diameter for constant mass rates of flow gives higher flow rates of liquid and gas per unit area, and so higher pressure drops and larger pumping costs.  At the same time, increasing the column diameter gives larger equipment costs.  Thus there will be an economic optimum diameter depending upon relative costs and the relation between pressure drop and flow rates.

Experimental Apparatus

The packed column is a 9-foot QVF glass tower with an inside diameter of 5.84 inches.  It contains 5/8-inch pall rings as packing in a bed approximately 5 feet deep (measure more exactly).  It is fitted with a small gas saturator upstream of the tower to minimize evaporation of water in the main column during as absorption

A Roots blower supplies air to the system.  Gas flow can be controlled with the variable speed drive and/or a bypass valve.  Manometers filled with various liquids measure blower exhaust pressure, pressure drop across the orifice, and pressure drop across the column.  The orifice is of diameter 1.501 inches in a pipe of diameter 2.067 inches, and the orifice coefficient can be taken as 0.61

Water flow rates are determined with a rotameter.  The calibration curve is posted near the column.  Adjustable legs are provided to adjust water levels while maintaining liquid seals to prevent leakage of gas.

Procedure

(a)        With dry packing (no water) use four widely different gas flows, with the highest flow giving a pressure drop over the packed column of about 10 cm. of methanol.  The bypass valve should be used to get the smallest flows.  Measure flows and pressure drops.  Remember that gas temperature and absolute pressure will be needed.

(b)        Pressure drops for wet packing should be measured for a minimum of four different gas flows for each of three different liquid flows.  The gas flows should be over about the same range as in part (a).  The largest liquid flow should be close to the maximum water flow posted on the control panel, and the range should be as wide as practical.  Note that water flows above the posted maximum may force water into the manometer containing fluid.

(c)        At the highest liquid flow of part (b), further runs should be done at successively higher gas flows (each one giving a pressure difference across the orifice about 20% larger than the one before).  For each run, besides measurements of flows and pressure drops the appearance of the system at all points should be noted.  The gas flow should be increased until signs of flooding are observed.

Calculations and Technical Report

(a)        From your experimental data, to what power (exponent) of the mass velocity is the pressure drop for dry packing proportional?  Does this indicate that the flow is laminar or turbulent?  Is this result consistent with the relative size of the two terms of the Ergun equation?

(b)        Compare the measured pressure drops for dry packing with the correlation given by the Ergun equation (see Treybal1).  Note that the pressure difference across the orifice can be related algebraically to G, the superficial mass velocity of gas in the packed column.  Thus it is not necessary to calculate intermediate quantities such as the superficial linear velocity in the column.

(c)        Compare your measured pressure drops for wet packing with the two attached generalized correlations (due to Eckert et al.) which are found in Treybal (Figure 6.34)1 and Bennett and Myers (p. 613)2.

(d)       Plot log (DP) vs log G for each value of L, the mass velocity of the liquid.  Compare the flooding point indicated by this plot with the flooding point observed visually based on the correlation of B. Milne (1994) on the next page. This is a generalized correlation of the form equivalent to the graphic in Treybal(1980) Figure 6.34.

(e)        Design, on the basis of your measurements rather than the correlations in the literature, packed with the same packing as in the laboratory and at the same liquid mass velocity as for your highest liquid flow, a column to treat 5,000 kg/h of gas if the gas rate is to be 65% of the flooding rate?  What pressure drop per foot of packing would be expected?

Technical Letter

Give a Brief comparison between your experiment results and those in the literature and then present the results of your design study.