Introduction
In this practical, there were three parts in which basic skills and key ideas were put into practice as they are essential to working in the laboratory in order to get reliable and valid results; one of the basic skills put into practice was pipetting. This was the main objective for the whole practical, as pipettors are the fundamental tools used to measure liquids in laboratories. Not only did this develop the skills and confidence acquired for using pipettes, but it also gave an idea for what pipette would be best to measure out specific volumes for part three of the practical, which entailed finding out the concentration of a salt in an unknown substance by finding its density and comparing it to the density of water which is 1Kg. It was believed that the mechanical pipettor was going to be more accurate than the serological pipettor as the mechanical pipettor is renowned for accurate liquid dispensing.

Methods
The first part of the experiment consisted of the use of a 1000 µl mechanical pipettor and a serological pipette to pipette 1000 µl of pure water into a weighing boat on the scales to gain a weight of 1000 grams. This was repeated 3 times to increase the chances of gaining reliable data. After gaining the data, the average and standard deviation for both pipettes were calculated. In the second part of the practical, a 100 µl pipettor was included in addition to the previous two pipettes used in the first part of the practical. With each pipette, 100 µl of pure water was again pipetted which was repeated three times to increase the reliability. After retrieving the data, the average and standard deviation for all three pipettes were calculated. In the third part of the practical, water was measured at different volumes using a pipette of choice. This was based on the understanding of which pipette would produce an accurate and precise measurement for the specific volumes. This was...

...Determining the accuracy of varieties of pipettes by weighing and finding the density of a liquid
Abstract
Different varieties of pipettes (P100, PR1000 pipettors and a serological pipette) along with a weighing balance was used in this investigation to check the density of an unknown liquid by first finding out what the liquid weighed and plotting a graph of the mass in grams against the volume of the liquid used in micro litres (µl) and finding the gradient of the graph (∆Y/∆X). Most of the standard deviation values were small showing that they were very close to the mean (average) hence more precise readings were obtained. The results from the graph also showed that the density of the unknown liquid A and B was denser that water and that is because it contains other dissolved substances which increased the overall weight.
Introduction
Pipetting requires a lot of skill to acquire precision and accuracy. For example the pipette tip must be pre-wet about three times before it is dipped into the solution [1] because dry and pre-wet pipette tips reveal greatest discrepancies. Dry pipette tips consistently deliver significantly lower volumes than did the pre-wet tips [2-6]. This can influence the readings showing on the balance as lower volumes will record lower mass and higher volume will record a higher mass which will in turn affect the density which will be measured making the...

...
Experiment
Density, Accuracy, Precision And Graphing
OBJECTIVES
1. The determination of the density of water
2. A comparison of the accuracy and precision of a graduated cylinder and a pipet
EXPERIMENTAL MATERIALS
Part A
A 50mL graduated cylinder
A balance
50.0mL deionized water
A rubber policeman
Part B
A 100mL beaker
A 50mL graduated cylinder
A volumetric pipet
120.0mL deionized water
A thermometer
A rubber policeman
EXPERIMENTAL METHODS
Part A: Density of water
1. An empty, dry 50mL graduated cylinder was obtained.
2. The mass of graduated cylinder with using a balance.
3. 10.0mL of deionized water was added to the 50mL graduated cylinder.
4. Mass of 10.0mL of deionized water + the cylinder was measured with balance.
5. To take only mass value of the 10.0mL deionized water, the mass value of the graduated cylinder was subtracted from the mass value of the 10.0mL of deionized water + the cylinder.
6. Density of 10.0mL of deionized water was calculated by its’ mass and volume. (d=m/v)
7. The exact density of the 10.0mL of deionized water was recorded on the data sheet.
8. Deionized water was added up to the 30.0mL mark of the 50mL graduated cylinder and Steps 3 to 7 were repeated for 30.0mL.
9. Deionized water was added up to the 50.0mL mark of the 50mL graduated cylinder and Steps 3 to 7 were repeated for 50.0mL.
Part B:...

...Experiment #4
Weighing and Volumetric Techniques – Accuracy and Precision
Abstract
The purpose of this experiment is to become familiar with proper techniques for using the analytic balances, graduated cylinder, burette and pipette and determine which is more accurate and/or precise. In this experiment, the burette and pipette were more exact than the graduated cylinder and the analytic balance gave a very accurate and precise answer.
Results / Report
1) Weighing Copper
Copper sample #: 1
Balance #: 14
Temperature: 22.8EC
Weighing Attempt # Mass of Copper Sample (g)
1 3.1234
2 3.1233
3 3.1235
4 3.1232
Average Mass
= (3.1234g + 3.1233g + 3.1235g + 3.1232g) ÷ 4
=3.1234g
Standard Deviation
( - ) ( - )
3.1234 0 0
3.1233 -
3.1235
3.1232 -
Σ =
Or 0.0001
2) Burette Readings
a) Graduated Cylinder b) Pipette
Initial Volume (mL) 44.72 44.91
Actual amount added (mL) Actual amount added (mL)
1st 34.81 9.91 1st 34.98 9.93
2nd 24.90 9.91 2nd 25.00 9.98
3rd 15.05 9.85 3rd 15.08 9.92
Graduated Cylinder average
( 9.91±0.01 mL + 9.91±0.01 mL + 9.85±0.01 mL ) ÷ 3
= 9.89±0.03 mL
Pipette average
(9.93±0.01 mL +...

...01.07 Accuracy and Precision: Balance Lab Worksheet
Data
* Below is the table that you will complete for the virtual lab. Either type your results into this table or print the table from the virtual lab (it must be submitted to receive full credit for this assigment.)
* To print from the virtual lab.
1. Be sure the data table is viewable.
2. Right-click (PC) or Command-Click (Mac) on the table and select print.
Part I: Density of Unknown Liquid |
| Trial 1 | Trial 2 | Trial 3 |
Mass of Empty 10 mL graduated cylinder (grams) | 25.50 | 25.50 | 25.50 |
Volume of liquid (milliliters) | 8.10 | 8.30 | 8.10 |
Mass of graduated cylinder and liquid (grams) | 35.50 | 36.00 | 35.50 |
Part II: Density of Irregular-Shaped Solid |
Mass of solid (grams) | 38.285 | 42.345 | 42.577 |
Volume of water (milliliters) | 51.00 | 50.95 | 52.90 |
Volume of water and solid (milliliters) | 55.50 | 55.90 | 56.95 |
Part III: Density of Regular-Shaped Solid |
Mass of solid (grams) | 27.00 | 26.50 | 25.50 |
Length of solid (centimeters) | 5.25 | 5.00 | 4.50 |
Width of solid (centimeters) | 3.00 | 4.00 | 3.50 |
Height of solid (centimeters) | 2.50 | 3.00 | 2.00 |
Calculations
Show all of your work for each of the following calculations and be careful to follow significant figure rules in each calculation.
Part I: Density of Unknown Liquid
1. Calculate the mass of the liquid for each trial. (Subtract the mass of the empty...

...Erica Alonso
Chemistry Honors 1
Mr. Cunningham
1.07 Accuracy and Precision
Procedure
Access the virtual lab and complete the experiments.
Data
• Below is the table that you will complete for the virtual lab. Either type your results into this table or print the table from the virtual lab (it must be submitted to receive full credit for this assignment.)
Part I: Density of Unknown Liquid
Trial 1 Trial 2 Trial 3
Mass of Empty 10 mL graduated cylinder (grams) 26 25.6 26
Volume of liquid (milliliters) 8.6 8.7 8.5
Mass of graduated cylinder and liquid (grams) 36.5 36.5 36.7
Part II: Density of Irregular-Shaped Solid
Mass of solid
(grams) 38.384 41.435 41.951
Volume of water (milliliters) 51 50 52
Volume of water and solid (milliliters) 57 55 58
Part III: Density of Regular-Shaped Solid
Mass of solid (grams) 28.1 26.1 26.2
Length of solid (centimeters) 5.25 5 4.5
Width of solid (centimeters) 3 4 3.5
Height of solid (centimeters) 2.5 3 2
Calculations
Show all of your work for each of the following calculations and be careful to follow significant figure rules in each calculation.
Part I: Density of Unknown Liquid
1. Calculate the mass of the liquid for each trial. (Subtract the mass of the empty graduated cylinder from the mass of the graduated cylinder with liquid.)
Trial 1- 10.5
36.5-26= 10.5
Trial 2- 10.9
36.5-25.6= 10.9
Trial 3- 10.7
36.7-26= 10.7
2. Calculate the density of the unknown liquid for each...

...P H A R M AC E U T I C A L application note
Checking the accuracy of
PERKIN-ELMER POLARIMETERS
H. Stenz, Bodenseewerk Perkin-Elmer GmbH
Abstract
Quartz standards, sucrose solutions and optically active pure liquids are discussed as potential polarimetry standards. It is suggested to preferably use quartz standards for checking the accuracy of Perkin-Elmer polarimeters. Quartz standards are absolutely stable, have a high accuracy and are easy to use.
For laboratories working in an environment which is governed by GLP or GMP principles, it is compulsory to regularly check the accuracy of the analytical instruments used. The methods to be employed for these checks inevitably depend on the type of instrument concerned. This paper reviews the methods and standards which are commonly used (or have been considered in the literature) to check the accuracy of Perkin-Elmer precision polarimeters (Model 341 and Model 241 families of instruments). Before entering into this discussion, it is helpful to briefly describe the operating principle underlying Perkin-Elmer polarimeters. PerkinElmer polarimeters employ an optical null principle with automatic analyzer adjustment. An optically active sample generates an electrical signal which in turn drives a motor linked to the analyzer of the instrument via a precision gear train. This signal rotates the analyzer by exactly the angle by which the sample has...

...Precision describes the closeness of results that have been obtained in exactly the same way while accuracy indicates the closeness of the measurement to its true value. This experiment was used to determine the accuracy and precision of different volumetric measuring devices, as well as determining the density of an unknown metal. This lab was to help understand the application to volumetric measurements.
Part 1:
First, the next-to-smallest beaker was cleaned, dried, and weighed on the scale where it’s mass was determined. The container was then tared so the scale would only read the mass of the water. The smallest beaker was used to measure out 14 mL of water. Then, that waster was poured into the pre-weighed beaker and put on the scale. Once the measurement was recorded the beakers were both cleaned and dried. This process was repeated two more times.
Second, a 100 mL graduated cylinder was used to measure out 14 mL of water. Then, that water was poured into the pre-weighed beaker and put on the scale. Once the measurement was recorded, the beaker and graduated cylinder were both cleaned and dried. This process was repeated two more times.
Third, a 25 mL buret was used to measure out 14 mL of water. Then, that water was poured into the pre-weighed beaker and put on the scale. Once the measurement was recorded, the beaker and buret were both cleaned and dried. This process was repeated two more times.
After recording the mass...