The Laboratory Notebook

Fall Term

General Considerations:

The maintenance of a laboratory notebook is an important part of any laboratory experience. These written records of what takes place in the laboratory are critical to the practice of chemistry and other laboratory sciences. In the real world, they are the basis for:

1. published results of investigations (which usually summarize laboratory procedures)
2. verification and reproduction of important procedures
3. determination of claims of discoveries and ownership of inventions

The objective of a laboratory notebook write-up is to give sufficient information in the way of procedures and observations to permit another scientist to be able to tell what was done in the laboratory so as to be able to reproduce the procedure and get the same result.

Laboratory notebooks are particularly critical when unusual or unexpected results are obtained. Discoveries and inventions are extreme examples of unusual results. The acceptance of such findings by the scientific community generally depends on independent reproduction of the finding, i.e., the experiment must be reproducible by an independent investigator. An example of an irreproducible, unusual finding was the much publicized announcement of the production of large amounts of energy through "cold fusion."

What should go into a laboratory notebook?

• The pages should be numbered sequentially and they should never be removed.
• Entries should be make in ink and there should be no erasures - errors should be clearly lined out and replaced with corrections.
• The notebook should be a complete record of what was done.
  • Completeness is more important than neatness.
  • Where appropriate, conclusions should be included.
• Entries should be dated.
• Unusual environmental conditions should be noted.
  • e.g., an impending hurricane or blizzard, extremes in ambient temperature or humidity, power failures or surges.

What should NOT go into a laboratory notebook?

• Lecture notes, personal matters, material from other courses

In a laboratory such as that associated with a course, there are a few other considerations that could turn out to be important. For example, several analytical balances may be available. It is important to note which one is used in a weighing and to note if different balances are used to determine initial and final weights. If more than one container of a reagent is available, it is important to note if samples of the same material are taken from different containers.

A student laboratory notebook should permit the determination of what step or steps in a procedure may have introduced discrepancies (e.g., when unknowns are involved, or when different results are reported on the same known material). This is especially important if part of the experiment is the development of your own procedure.

Devices:

Ideally, when performing quantitative procedures, the devices used (balances, burets, pipets, volumetric flasks, etc.) should be calibrated. In an organic chemistry laboratory, time does not generally permit calibrating such devices.

Some types of errors will be minimized by consistently using the same device for the same type of measurement, i.e., the use of the same balance for weighing an empty vial and the same vial after adding sample. Consider an extreme example.

A buret has been incorrectly, but consistently marked so that each major unit (mL) is actually 1.1 mL. If the same buret is used to standardize a reagent solution and to titrate an unknown solution, the absolute error in accuracy caused by the incorrect markings will cancel. If the standardization is carried out using the inaccurate buret and a different, correctly marked buret is used in titrating the unknown, a 10% error in accuracy will result.

Whenever possible, a unique identifier of a device should be recorded. If the device does not appear to function as expected, a comment to that effect should be noted. If there is a significant malfunction, the attention of an instructor is mandated.

Reagents:

Again, ideally, the student investigator should prepare all the necessary reagents for an exercise. Preparing a reagent means noting the purity and assay of the starting materials and using the appropriate quantitative techniques for the preparation of solutions. In the introductory laboratory, stock solutions are often provided to save time. An individual student has little control over the quality of the reagents provided. Assuming that no one has changed the stock chemical in any way, it should contain what its label indicates. At the very least, the laboratory notebook should indicate the data on the label of the stock solution (with the appropriate number of significant figures).

Instrumentation:

When instrumentation is used in an experiment, it is important that the instrument be completely characterized. For example, in using a gas chromatograph, you should note the type of instrument, i.e., a Gow-Mac (including the model number) with thermal conductivity detector; the carrier gas and the flow rate; the type of column (length, diameter, packing material, etc.); injector temperature; detector temperature; column oven temperature; any temperature programming that was done. Equivalent information should be recorded for any instrument you use. You should supply all the information that would be necessary for someone else to duplicate your experimental results.

Other Materials:

In instances where the student provides some of the materials for an exercise, the identity of the material should be recorded in detail, along with any relevant data.

Consider, for example, that you are going to determine the composition of buffered aspirin. The following information about the origin of the aspirin sample should appear in the notebook:

Misc.:

The following list gives more information about what should be in your notebook. It was adapted from the graduate school notebook of Dr. Brian Coppola of the University of Michigan - Ann Arbor. (Note that the actual entries in his notebook were handwritten in ink.)

Your notebook should include:

• Numbered pages with dated (and timed where relevant) entries.
• A title for the experiment and, if you are doing a synthesis, such as making a derivative, the balanced equation of the planned reaction scheme.
• Any references or citations that were used to prepare a procedure for the experiment (e.g., the page numbers in this Course Pack, or the laboratory textbook; the literature reference if the procedure was adapted from a journal article). textbook; the literature reference if the procedure was adapted from a journal article).
• A data table (refer to the sample data table on page 27 of the Course Pack, or link to the web site) of reagent names, molecular weights, densities, concentrations, amounts used, molar equivalents, and any other useful information (e.g., source of material, purification method). Never write experimental data on a piece of paper and then copy the data into your notebook. If you forget to take your notebook with you to the balance or another measuring device and must resort to using a piece of paper to record the results, tape the paper into your notebook with the original data on it. It is very easy to make transcription errors!
• A safety table (refer to the sample safety table on page 32 of the Course Pack, or link to the web site) with safety information about all the chemicals you will be using or preparing. Information about the chemicals is available on line in the Chemical Database.
• The planned procedure, which can be written in the notebook beforehand and modified with changes and observations as you run the experiment. For most of the experiments you do, you will keep a running account of your procedures and observations as you carry out the experiments rather than write the procedure beforehand.
• A flow diagram (refer to the sample flow diagram on page 10 of the Course Pack, or link to the web site) for any preparations showing the procedure you plan to use to purify the product or products.
• Chromatographic data should include a drawing, solvents used, visualization methods, labels, calculations of R_f for TLC; type of column used, retention times, oven temperatures, for GC, etc. Similar information should be recorded for column chromatography. TLC plates should be taped into your notebook with clear tape over the top to protect the surface from damage. An accurate colored drawing should also be made. GC traces should be kept in a folder at the back of the notebook and the retention times from the GC trace should be summarized in a data table.
• Crude masses, purification methods, yields (refer to the sample calculation of percent yield on page 15 of the Course Pack, or link to the web site).
• Spectral data should be tabulated and referenced. IR spectra should be kept in a folder at the back of the notebook and the results from the spectra should be summarized in a data table. Include only the important absorbances and an indication of which functional group an absorption suggests is present in your sample.
• For a synthesis include in the data tables (refer to the sample data table on page 32 of the Course Pack, or link to the web site) the predicted product (its name, structural formula, molecular weight, physical properties such as bp or mp, theoretical yield (refer to the sample calculation of percent yield on page 15 of the Course Pack, or link to the web site).
• Any and all manipulations performed and observations that are made.
• "continued to page..." and "continued from page..." labels if needed if you have used more than one page for the experiment. The pages do not have to be contiguous. If you are working on more than one experiment at a time and run out of pages, you can continue the experimental details on a later page if you indicate on which page the rest of experiment is to be found.
• Calculations (including any prelab calculations)!
• Speculations!!!
• Accidents (all accidents must be reported to the instructor)!!!
• Spills (all spills must be reported to the instructor)!!!

All the information in the world won't do you or anyone else any good if it is not organized and it cannot be retrieved conveniently. Long essays and data that are scattered throughout the pages are a nightmare! There should be a natural flow to the information, and it should be blocked out in a way that is pleasing to the eye (with the idea that someone else might need it). It is appropriate to prepare summary pages for yourself at the end of an experiment, or at the end of a block of experiments, so that you can remind yourself about where you've been. Summary pages that are written as soon as possible after completing an experiment will make it easier to write accurate reports.

The laboratory notebook is both a record of what was done and a legal document. You can link to Dr. Coppola's notebook to see an example. To make the example more legible, the example has been typed rather than scanned in (Dr. Coppola's handwriting is sometimes difficult to read). The actual notebook entries are in small type. Explanations of the entries are in large type. Your notebook, of course, will be handwritten in ink. You should adopt this kind of format or create a better one. Reread pp. 22-29 in Pavia for alternate styles. The American Chemical Society has published a paperback book on how to keep a laboratory notebook. If you want a copy for your personal use, you can order it from the ACS. You do not need long dissertations about statements of purpose, etc.; you should include essentially the kind of information explained in boldfaced type. It is very important, however, that you record your data in your notebook as you take it. DO NOT SCRIBBLE INFORMATION ON A PIECE OF SCRAP PAPER AND THEN RECOPY IT INTO YOUR NOTEBOOK. It is easy to make transcription errors. If you accidentally forget your notebook and do not have time to go back to get it before recording data, paste in your notebook the scrap paper on which you recorded your data. IF YOU MAKE A MISTAKE WHILE RECORDING DATA OR IN A CALCULATION, JUST CROSS OUT THE MISTAKE AND CONTINUE. DO NOT ERASE ANYTHING YOU RECORD IN YOUR NOTEBOOK AND NEVER TEAR PAGES OUT OF THE NOTEBOOK. YOUR NOTEBOOK IS THE ONLY LEGAL EVIDENCE THAT YOU HAVE THAT YOU DID WHAT YOU CLAIM TO HAVE DONE.