Keeping a Notebook (Laboratory Manual)

 

By : James W Zubrick
Email: j.zubrick@hvcc.edu

A research notebook is perhaps one of the most valuable pieces of equipment you can own. With it you can duplicate your work, find out what happened at leisure, and even figure out where you blew it. General guidelines for a notebook are:

1. The notebook must be bound permanently. No loose leaf or even spiral-bound notebooks will do. It should have a sewn binding so that the only way pages can come out is to cut them out. (8 1/2 x 11 in. is preferred).

2. Use waterproof ink! Never pencil! Pencil will disappear with time, and so will your grade. Cheap ink will wash away and carry your grades down the drain. Never erase! Just draw one line through yuor orrcro your errors so that they can still be seen. And never, never, never cut any pages out of the notebook!

3. Leave a few pages at the front for a table of contents.

4. Your notebook is your friend, your confidant. Tell it:

a. What you have done. Not what it says to do in the lab book. What you, yourself, have done.

b. Any and all observations: color changes, temperature rises, explosions . . . , anything that occurs. Any reasonable explanation why whatever happened, happened.

5. Skipping pages is extremely poor taste. It is NOT done!

6. List the IMPORTANT chemicals you’ll use during each reaction. You should include USEFUL physical properties: the name of the compound, molecular formula, molecular weight, melting point, boiling point, density, and so. The CRC Handbook of Chemistry and Physics, originally published by the Chemical Rubber Company and better known as the CRC Handbook, is one place to get this stuff.

Note the qualifier “USEFUL.” If you can’t use any of the information given, do without it! You look things up before the lab so you can tell what’s staring back out of the flask at you during the course of the reaction.

Your laboratory experiments can be classified to two major types: a technique experiment or a synthesis experiment. Each requires different handling.

A TECHNIQUE EXPERIMENT

In a technique experiment, you get to practice a certain operation before you have to do it in the course of a synthesis. Distilling a mixture of two liquids to separate them is a typical technique experiment.

Read the following handwritten notebook pages with some care and attention to the typeset notes in the margin. A thousand words are worth a picture or so (Figs. 2-4).

Notebook Notes

1. Use a descriptive title for your experiment. Distillation. This implies you’ve done all there is in the entire field of distillation. You haven’t? Perhaps all you’ve done is The Separation of a Liquid Mixture by Distillation. Hmmmmmm.

2. Writing that first sentence can be difficult. Try stating the obvious.

3. There are no large blank areas in your notebook. Draw sloping lines through them. Going back to enter observations after the experiment is over is not professional. Initial and date pages anytime you write anything in your notebook.

4. Note the appropriate changes in verb tense. Before you do the work, you might use the present or future tense writing about something that hasn’t happened yet. During the lab, since you are supposed to write what you’ve actually done just after the time you’ve actually done it, a simple past tense is sufficient.

A SYNTHESIS EXPERIMENT

In a synthesis experiment, the point of the exercise is to prepare a clean sample of the product you want. All the operations in the lab (e.g., distillation, re crystallization, etc.) are just means to this end. The preparation of 1-bro-mobutane is a classic synthesis, and is the basis of the next series of handwritten notebook pages.

Pay careful attention to the typeset notes in the margins, as well as the handwritten material. Just for fun, go back and see how much was written for the distillation experiment, and how that is handled in this synthesis (Figs. 5-10).

Once again, if your own instructor wants anything different, do it. The art of notebook keeping has many schools — follow the perspective of your own.

Notebook Notes

1. Use a descriptive title for your experiment. n-Butyl Bromide. So what? Did you drink it? Set it on fire? What?! The Synthesis of 1-Bromobutane from 1-Butanol—now that’s a title.

2. Do you see a section for unimportant side reactions? No. Then don’t include any.

3. In this experiment, we use a 10% aqueous sodium hydroxide solution as a wash (see Chapter 11, “Extraction and Washing”), and anhydrous calcium chloride as a drying agent (see Chapter 7, “Drying Agents”). These are not listed in the Table of Physical Constants. They are neither reactants nor products. Every year, however, somebody always lists the physical properties of solid sodium hydroxide, calcium chloride drying agent, and a bunch of other reagents that have nothing to do with the main synthetic reaction. I’m specially puzzled by the listing of solid sodium hydroxide in place of the 10% solution.

4. Theoretical yield (not yield) calculations always seem to be beyond the ken of a lot of you, even though these are exercises right out of the freshman year chemistry course. Yes, we do expect you to remember some things from courses past; the least of which is where to look this up. I’ve put a sample calculation in the notebook (Fig. 7), that gets the mass (g) of the desired product (1-bromobutane) from the volume (ml) of one reactant (1-butanol). Why from the 1-butanol and not from the sulfuric acid or sodium bromide? It’s the 1-butanol we are trying to convert to the bromide, and we use a molar excess (often abbreviated XS) of everything else. The 1-butanol is, then, the limiting reagent; the reagent present in the smallest molar ratio. Note the use of the density to get from volume to mass (ml to g), molecular weight to go from mass to number of moles (g to mol), the stoichiometric ratio (here 1:1) to get moles of product from moles of limiting reagent, and finally reapplication of molecular weight to get the mass (g) of the product. Note that this mass is calculated. It is NOT anything we’ve actually produced. In THEORY, we get this much. That is theoretical yield.

5. I’m a firm believer in the use of units, factor-label method, dimensional analysis, whatever you call it. I KNOW I’ve screwed up if my units are (g l-butanol)2/mole 1-butanol.

6. Remember the huge write up on the Separation of a Liquid Mixture by Distillation, drawings of apparatus and all? Well, the line “the mixture was purified by distillation,” (Fig. 9) is all you write for the distillation during this synthesis.

7. At the end of the synthesis, you calculate the percent yield. Just divide the amount you actually prepared by the amount you calculated you’d get, and multiply this fraction by 100. For this synthesis, I calculated a yield of 25.44 g of product. For this reaction on the bench, I actually obtained 16.2 g of product. So: (16.2 g/ 25.44 g)(100) = 63.6% yield)