Lab Notebook Guidelines for CHEM 330

Introduction - The purpose of a lab notebook

Your lab notebook is the single exact, permanent, legally defensible, archival record of what you did in lab. In an academic setting, notebooks are often used by the person who wrote the notebook or a lab colleague when trying to repeat an experiment, process data, or publish results. In a professional setting, they may be used to communicate work to new employees, defend against patent lawsuits, or support forensic or toxicological conclusions in a court of law. A good test of your lab notebook is to imagine handing it to a peer who has never completed the lab. Then, try to determine if there would enough information for them to (1) complete the lab with no other resources, (2) exactly repeat your data analysis and calculations and arrive at the exact same answer (including all significant digits), and (3) understand your conclusions and how you arrived at those conclusions. When in doubt, it's better to include too much than too little!

In the context of Aquatic Chemistry, you may imagine working in an EPA-certified water anlysis lab where a lack of thorough records may lead to the company losing EPA certification. Or perhaps one may work for an environmental consulting firm that conducts water analysis that is the key evidence in a court case against a polluting entity – in such a case a good lab notebook could make or break the defense or prosecution! You should record everything in your lab notebook – during lab, not after!

Specific Requirements for CHEM 330

1. Include all relevant parameters you set on the instruments you use. For example, if you use a spectrophotometer and have to set the collection wavelength, you should include that in your notebook.

2. Include the lot or batch numbers for all chemicals you use. This is important in case contamination in the chemicals is found.

3. Include detailed sample descriptions / IDs, and make sure to keep track of these throughout the analysis.

4. Include the following sections:

   1. Title: Each lab should contain a title clearly indicating what you were working on that day.

   2. Introduction: A brief (several sentence) overview of what the lab is about and what you hope to find. Include references to any standard methods or literature you find that's relevant to the experiment. Also clearly state the problem you are trying to solve and what you expect to happen.

   3. Materials and Methods/Procedures: See below for more information.

   4. Results and Calculations: This is where you should put any data tables and calculations. Your data and calculations should be recorded first in your notebook and then transferred to an electronic format if necessary. The only exceptions are when data is exported in an electronic format from an instrument – in that case do your best to include it in your notebook, and specify the filename and location where the file is saved in your notebook.

   5. Discussion and Conclusions: A brief (1-2 paragraphs) summary of the experiment and outcomes. Did the experiment go as expected? Did anything go wrong? What could you do differently to improve the experiment next time? It is also good to compare your results to prior work / literature sources / standard values in this section (and include reference for where you found the numbers). For example, if you are measuring copper in drinking water, you might say whether or not your value is below the EPA limit and cite the EPA rule where that limit is given.

Writing Your Procedures

Your procedures in your notebook should state exactly what you did. Exactly! This is your exact record you could use to redo calculations, remember what the sample looked like, remember what special steps you took on the instrument, etc. This is not the same as the methods in a paper or lab report; those are a summary of what you did.

• Write all procedures in past tense. Do not just copy the handout.

  • Good: I added 1.0162 g of acetaminophen to a 200-mL volumetric flask and brought to volume with ultrapure water.

  • Bad: Add 1 g of acetaminophen to 200 mL of water.

  • Explanation: The lab notebook is a record of what you did, not a cookbook. If you were telling a friend about your vacation you wouldn't say "Get on a plane. Fly to Europe. Go to hotel.", you would say "I flew from Atlanta to Paris, and then stayed at a hotel in the city center." Your lab notebook is no different. More importantly, the difference in significant digits is drastic. In the first example, the results will be limited to 5 significant digits by the balance (the balance reports 4 decimal places, or 5 SF in this case, and the volumetric flask contains 200 +/- 0.15 mL); in the second, all that precision has been thrown away and we're left with a single significant digit. Finally, the second provides no indication as to the purity of the water used, although this is very important for trace instrumental analysis.

• Include direct observations.

  • Good: Upon collection, I saw that the e-cigarette liquid had turned from clear-yellow to clear-brown after aerosolization.

  • Bad: e-Cigarette liquid was collected.

  • Explanation: The first example includes pertinent observations of exactly what occurred when the step was performed. This helps someone who is doing the lab for the first time know what to expect, and helps you remember what happened when you're going back through your notes. Importantly, the color change probably indicates a chemical change occured in the sample, which may be worth investigating later.

  ⚠ Note

  Some students like to write out their procedures before coming to lab to help in planning. This is great! However, these will by default be general procedures and not exactly what you did. So if you do this, you should leave room to add exactly what you did – and make sure you do in fact add it in during lab!

Significant Figures and Errors

• Balances: The exact number of significant digits from the balance may depend on which balance you use. Be sure to record all digits on the balance when mass is important, even if they are zeroes; if the last digit fluctuates do the best you can to estimate it. Remember you do NOT have to weigh out the masses exactly as they appear on the worksheet – what matters is that you get close and that you record the actual exact mass you used!

• Volumetric Glassware: All volumetric pipettes and flasks are labeled with the volume of water they deliver or contain at room temperature along with the error associated with that volume. Use this to determine your significant digits. Flasks should be used to contain liquid (marked TC) and pipettes should be used to deliver liquid (marked TD); if your pipette has lines for both make sure you use the correct one (TD).

• Graduated cylinders: For small volumes, these typically have 3 significant digits. You should interpolate to at least the nearest 0.5 mL when using a small or medium-sized graduated cylinder. Remember, there is a large difference between recording 10 ml and 10.5 ml in your notebook in regards to significant figures (1 vs 3)! Most work in this course should use volumetric glassware and not graduated cylinders.

• Beakers/Erlenmeyer Flasks: These should not be used to measure volumes! They are just for temporarily holding solutions or performing a reaction / extraction.