Calibration of Glassware - Lab Report Example

This exercise deals with calibration of two volumetric glassware that are used in analytical chemistry; burette and canonical flask. These tools are extensively used in analysis in the laboratory. Calibration was carried out by getting the mass of required apparatus and liquid. First of all, weigh the empty canonical flask. Then fill the pipette/burette with water till the water reaches the mark on the burette/pipette. Thereafter, transfer the measured water into the canonical flask. Now weigh the canonical flask when it is filled with water.

Repeat the same procedure three times for reproducibility. Get rid of all the water in the canonical flask. All the other volumes of water marks in canonical flask will be measured by the balances that read to ±0.0001 g for this experiment. The only exception will be the calibration of 100 mL volumetric flask mark. For that mark, one should use the balances that read to ±0.001 g because they can handle heavier weights. The estimated uncertainties are weight of water, error in sighting the level of the water, density of water and error in temperature reading.

So as to avoid introducing random and systematic errors in measurements, it is essential to calibrate them.IntroductionThe main goal of this exercise is to calibrate these volumetric glass wares:• 50 mL burette•10 mL pipette•25 mL pipette•50 mL volumetric flask•100 mL volumetric flaskObtained from: http://en.wikipedia.org/wiki/File:Brand_volumetric_flask_100ml.jpgVolumetric glassware is manufactured to specific standards, but it is not all identical and the manufacturing tolerances are not as strict as you may require for certain Lab measurements.

Indeed, small variations often occur from one piece of glassware to the next. It is possible to correct for systematic errors in the calibration markings, and such corrections are necessary for the most accurate analytical work.Experimental Section Recalibration is carried out by weighing the quantity of water contained in the volumetric container. The mass of the liquid is converted to required volume using density of water: Volume = mass/densityVolumetric measurements are affected by two main systematic errors; parallax and temperature.

The volume that a certain liquid occupies varies with temperature. Even the volume of the apparatus holding the liquid is also affected by the temperature. 21 degrees Celsius has been taken as normal room temperature for calibration. At times values of volume are corrected using the formula below V20 = V [1 + 0.000025 (20 - t)]Another source of systematic error when using volumetric apparatus is parallax. A correction to this error to this should be applied during procedures of calibration as indicated below.

Adapted from Quantitative Analysis, 4th Ed. by Conway Pierce, Edward L. Haenisch and Donald T. Sawyer; John Wiley & Sons; 1948.The correct readings are ensured by positioning the eye as the middle reading level above. Results and DiscussionThe significant data was obtained and included in the table and graph. Table 1 provides an example of the data used to calibrate Burette. Burette Calibration     Density of water (at 21 degrees C in gm/L):1.0030          Volume delivered (mL)1020304050Empty Wt. (g)29.230729.230729.230729.230729.2307Trial 1, water + glassware (g)42.579352.342962.136172.232082.

1303Trial 2, water + glassware (g)42.663052.358862.067572.200781.2264Trial 3, water + glassware (g)42.503052.352462.091772.250581.9815Trial 1, density corrected (mL)13.308723.043132.807042.872752.7414Trial 2, density corrected (mL)13.392123.058932.738642.841551.8402Trial 3, density corrected (mL)13.232623.052532.762742.891152.5930Mean (mL)13.311123.051532.769442.868452.3915Stdev (mL)0.07980.00800.03470.02510.4832%RSD0.59940.03460.10590.05850.9223Error (mL)3.31113.05152.76942.86842.3915Rounded Error (mL)33332The table also shows calculated mean and standard deviation.

This table contains as many as 50 trials in order to get more reliable estimation of the measurement uncertainties. The data value was arrived at by conducting a minimum of three trials to obtain a suitable calibration. All the findings were recorded in the format above.Table 2 indicates data used in calibrating volumetric glasswareVolumetric Glassware Calibration      Density of water (at 21 degrees C in gm/L):   1.0030            10mL pipette25mL pipette50mL flask100mL flaskEmpty Wt.(g)  29.230729.230736.471564.

07Trial 1, water + glassware (g)  39.127854.162386.0322163.41Trial 2, water + glassware (g)  37.590954.140686.0661163.47Trial 3, water + glassware (g)  39.841254.298386.0890163.41Trial 1, density corrected (mL)  9.867524.857049.412599.04Trial 2, density corrected (mL)  8.335224.835449.446399.10Trial 3, density corrected (mL)  10.578824.992649.469199.04Mean (mL)  9.5938224.895049.442699.06Stdev (mL)  1.14650.08520.02850.03%RSD  11.95090.34230.05760.03Error (measured - mtated, mL)  -0.4062-0.1050-0.5574-0.94The table also shows calculated mean and standard deviation.

The correction factor was calculated to plot the burette graph using this formula Correction Factor = Volume delivered – Volume indicated Thereafter, a graph was plotted of Average Buret Correction Factor vs. Volume Delivered in Excel.Figure 1 shows a burette graph The Y axis was labeled with correction values in mL while x axis was labeled with delivered volume in mL.Data analysis included calculation of mean values.Mean was calculated using the formulaMean = Trial1 + Trial2 + Trial3                               ———————–                                        3 Percentage Relative Standard Deviation was calculated using the formula below %RSD = SD/mean*100%ConclusionThe allowable percentage error was +- 0.03 %.The percentage error was calculated using the formula   (TV) – EV  X 100                              ———————–                                         TV  Where TV is theoretical volumeEV is experimental volumeTo improve on proper measurement of volumes, manual calibration of apparatus should be done regularly.

To also improve on their performance, volumetric flasks, which are usually colorless, they might be amber-colored so as to handle most light-sensitive compounds.References1. Bucher, J. (2007). The Quality Calibration Handbook: Developing and Managing a . Cincinnati, OH: ASQ Quality Press.2. Cable, M. (2005). Calibration: A Technicians Guide. New York: ISA. 3. Martens, H. & Naes, T. (1992). Multivariate calibration. New York: Wiley publishing. 4. Pierce, C., Haenisch, E. & Sawyer , D. (1948).Quantitative Analysis, 4th Ed.

New York: John Wiley & Sons.