Tag: writing

“The product in flask: data, quotes, looks;
The time that each task, new or rote, took;
Stoich calcs and dilutions;
Key findings; conclusions; 
Next questions to ask… all in notebook.”

The 11 April 2021 limerick returned to one of my favorite themes, the chemistry lab notebook, which I’ve explored a few times in this space before!    

“The product in flask: data, quotes, looks; /
The time that each task, new or rote, took…”

In this particular poem, it was fun to build towards “notebook” as the final rhyme, then shape the remainder of the limerick around it.  This required some stretching of vocabulary, at times, but within reason, as is ideally clear by taking one line at a time.  

A chemist would record information about “the product in flask: data, quotes, looks.”  What is the product’s mass? Its melting point?  What statements would the chemist wish to record about the experiment?  What does the product look like?       

Another common record included in the notebook would be “the time that each task, new or rote, took.”  Each step in an experimental procedure is either a new attempt or a repeated (“rote”) one; further, it’s useful to know how long certain steps (heating under reflux, stirring, etc.) can take.  

“Stoich calcs and dilutions; /
Key findings; conclusions…” 

The “A” rhymes in this limerick (with its AABBA form) all build on “notebook,” while the “B” rhymes are a bit less forced.  The phrase “stoich calcs and dilutions” refers to the lab-focused mathematics completed in a lab notebook (theoretical yield and other stoichiometric calculations, M₁V₁ = M₂V₂, etc.).  Perhaps the most obvious things to highlight in a lab notebook are the “key findings [and] conclusions” from a given procedure.    

“Next questions to ask… all in notebook.”

The final line of the poem highlights the self-perpetuating nature of scientific research: what “next questions” do the conclusions of a given experiment invite?  Those creative reflections are also an important part of a procedural record.  

“To isolate via filtration,
Consider the process notation:
Whether vacuum or gravity 
Will the product compatibly 
Obtain, through work-up situation.”

The 10 April 2021 limerick discussed two additional work-up techniques useful in the organic chemistry laboratory: vacuum filtration and gravity filtration. Each is accomplished via the use of a specific type of set-up requiring a specific type of funnel, a fact which provides this essay’s title.    

“To isolate via filtration, /
Consider the process notation…”

This poem notes the distinction between two different techniques with confusingly similar names (both involving filtration).  To complete an organic chemistry work-up and isolate a target compound, one must first decide which type of filtration is most useful, or “[c]onsider the process notation.”    

“Whether vacuum or gravity /
Will the product compatibly /
Obtain, through work-up situation.”

Often in organic chemistry lab, a chemist seeks to separate a liquid from a solid via some kind of filtration, a relatively simple task accomplished by using glassware and filter paper.  

If the target compound (the compound that the chemist wants to further analyze or use) is the solid, vacuum filtration is the work-up technique of interest.  By using (typically) a Büchner funnel covered with filter paper and creating a vacuum, the solid is isolated and thoroughly dried on that paper.  If the target compound is in the liquid phase, instead, then gravity filtration is used, with a glass stem funnel.  Here, the filter paper catches any unwanted solid byproducts, and the liquid that passes through the paper and funnel continues into the next step of analysis or synthesis.

The goal with either type of filtration is to “compatibly / [o]btain” the target product while avoiding any additional impurities: to remove as much “extra” material as possible.  If the product is a solid, then the vacuum set-up ensures that as much liquid as possible is removed.  If the product is a liquid, then the slower gravity filtration ensures that no extra solid material is accidentally carried along.  Common objectives in the lab involve learning both techniques and discerning between their optimal uses.   

“Assembling set-up, distillation,
Can lead to a bit of frustration.
Be sure to securely 
Clamp glassware so surely
Experiment defies ruination!”  

The 9 April 2021 Twitter limerick highlighted distillation, a lab technique used in organic chemistry laboratories to purify liquid samples.  The poem highlights one of the ways in which such a lab technique might go awry… and encourages students to avoid it!  

“Assembling set-up, distillation, /
Can lead to a bit of frustration…” 

The first semester of organic chemistry lab introduces techniques and tools one at a time, building to increasingly complex experiments in which their uses can be combined.  One such technique is distillation: separating a liquid mixture into its component parts, based on differences in their boiling points.

A “simple distillation” is typically one wherein two components of a liquid mixture have boiling points distinct from one another.  This mixture is placed in a round-bottomed flask, which is connected to a condenser, which is connected to a receiving flask.   The mixture is heated until it reaches the boiling point of the first component; at this point, the first component vaporizes, travels as a gas into the condenser, and is condensed into the first receiving flask.  (The condenser circulates cooling water through an outer jacket: within the complex set-up of the laboratory fume hood, one condenser tube connects to a faucet and the other to a drain.)  Once this first component is separated out, a second receiving flask is used to collect the second component, as its own boiling point is reached.    

Typically, these steps are all new for students; although they will become well-practiced with the distillation set-up, assembling it can be frustrating initially.   

“Be sure to securely /
Clamp glassware so surely /
Experiment defies ruination!”  

This set-up is often one of the first to involve multiple pieces of glassware– including, most notably, the condenser. To avoid “ruination” (the watery collapse of the endeavor!), it is important to clamp the pieces of glassware together and, further, to clamp everything securely within the hood itself. 

“Exacting; extracting… 
A sep funnel’s function:
To isolate layers and
Compound obtain.
(Avoid a moment most 
Melodramatical:
Ere product’s sure, 
From waste’s discard, 
Refrain!)”

The 8 April 2021 Twitter poem addressed another laboratory technique: using a separatory funnel, a specialized piece of glassware that allows a chemist to separate different components of a given reaction mixture (the environment in which the reaction has been taking place).  

“Exacting; extracting… /
A sep funnel’s function: /
To isolate layers and /
Compound obtain.”

Each step of an organic synthesis depends on two key parts: the reaction itself, which converts reactant to product, and the work-up, in which the product compound is isolated (identified and purified), while excess solvents and side materials are discarded.  

The separatory funnel (“sep funnel”), as its name suggests, is particularly useful in separating liquid layers from one another, based on their different densities.  Often, the layers of interest are “water” versus “non-halogenated organic solvents,” where the latter layer would be less dense than the former.  In the case of “water” versus “halogenated organic solvents,” through, the latter layer is more dense than the former.  (Chemists typically use “aqueous” and “organic” as efficient shorthand for the layers.)

Either way, depending on which layer the target product occupies, the chemist will use the sep funnel, to “compound obtain.”  

“(Avoid a moment most /
Melodramatical: /
Ere product’s sure, /
From waste’s discard, /
Refrain!)”

I suspect that anyone reading the discussion of different densities above, whether or not they are a chemist, might quickly note the most challenging hazard of using a sep funnel: being absolutely sure which layer is which (and which layer thus contains the product) before proceeding.  A best practice is to wait to discard the other layer until subsequent steps are completed, to be sure the target product hasn’t been accidentally lost: “Ere product’s sure, / From waste’s discard, / Refrain!”

When a student is learning the technique, though, this lesson can sometimes be hard-won.  This is unfortunately clear from the occasional “moment most / [m]elodramatical”… directly after the moment when someone’s synthesized product is inadvertently lost to the waste container.

“Consider lab drawer’s Bunsen burner…
Providing new role for chem learner
(Through method, flame-testing,
Steps towards metal-guessing):
Of cation’s ID, discerner.”  

The 7 April 2021 limerick summarized a qualitative analysis technique often used in introductory chemistry, which employs one of its most memorably named instruments, the Bunsen burner.  

“Consider lab drawer’s Bunsen burner… /
Providing new role for chem learner…”

Combustion can occur completely or incompletely.  Complete (stoichiometric) combustion is what is taught in the textbooks: a hydrocarbon fuel reacts with oxygen and is converted fully to carbon dioxide and water.  The path from start to finish actually occurs via a wide network of complex reactions involving radicals, which are species with unpaired electrons; these can cause all sorts of side reactions and products.  When the combustion is incomplete, these side reactions include the formation of soot.  Soot has many detrimental effects, and Robert Bunsen (1811-1899) was interested in developing a burner that could produce a particularly clean flame, avoiding these effects.  His burner has been widely adopted for use in introductory chemistry laboratories (by “chem learner[s]”).     

“(Through method, flame-testing, /
Steps towards metal-guessing): /
Of cation’s ID, discerner.”

A traditional and interesting use of the Bunsen burner is the flame test, or “method, flame-testing.”  A wire is placed into a solution made from an ionic compound, which includes a cation derived from a metal of interest.  The wire is then placed into the flame, and as the ionic solution evaporates, the flame will turn a certain color based on the emission characteristics of the metal ion in question.  For instance, copper would turn the flame a bluish-green, and potassium would turn the flame violet.  

If a student is given an unknown compound and asked to determine the cation in this compound, they could use the flame test behavior as a step towards identifying the unknown; their role as “chem learner” could then also include being “of cation’s ID, [a] discerner.”              

“Procedure today: use the crucible!  
Obtain sample’s make-up, deducible
Through tasks gravimetric 
And steps arithmetic;
Key data emerge, thus computable.”  

The 6 April 2021 limerick addressed another common laboratory technique: the use of a crucible, which can have applications both qualitative and quantitative in the chemistry lab.  

“Procedure today: use the crucible!”  

Crucibles are containers that can be heated to very high temperatures; as such, they are useful in a wide variety of chemistry settings.  In introductory chemistry, they typically inform some of the most interesting questions during lab check-in, as they aren’t as familiar and/or repetitive as some of the other materials in a lab drawer, such as flasks, beakers, or graduated cylinders.  

While the composition of crucibles can vary in industry and other settings, in the intro lab, crucibles are typically small ceramic dishes.  The main idea is that, when a crucible containing a sample of interest is heated, the sample will be affected by the heat (decomposing or otherwise reacting), while the crucible itself will be unaltered.  (In popular culture, the name is likely most familiar from Arthur Miller’s 1953 dramatic work, giving this essay its title.)  

“Obtain sample’s make-up, deducible /
Through tasks gravimetric /
And steps arithmetic; /
Key data emerge, thus computable.”  

One common use of the crucible is in a technique called gravimetric analysis.  By heating a reaction product to high temperatures in a crucible, it is possible to fully dry the product and obtain its exact mass (“tasks gravimetric”).  Through the use of that exact mass and the principles of reaction stoichiometry (“steps arithmetic”), a chemist can also determine the percent composition of a component ion, or analyte, in the pertinent starting material: “the sample’s make-up [is] deducible.”  

While this limerick emerged out of contemplating some rhymes (one more accurate than the other!) for “crucible,” it was a fun challenge to align the poem structure with a reasonable summary of the experiment. 

“With cylinder’s use (graduated),
A volume can be calculated…
Keep eye on meniscus;
Report results; discuss
The findings from lab extricated.”

This Twitter limerick was posted on 5 April 2021.  It (and, indeed, the next few as well) will pose some interesting challenges!  During this “week” of poems from April 2021, my goal was to take introductory chemistry lab routines and summarize them poetically. While it was fun to turn those everyday tasks into some brief, lyrical descriptions, I am less confident in my ability to expand on them here!  However, as I saw with this post, I still have much to learn regarding background information and etymology for even the most typical of lab routines.  

“With cylinder’s use (graduated), /
A volume can be calculated…”

A graduated cylinder is a common tool in an introductory chemistry student’s lab drawer. As the name suggests, this piece of glassware is cylindrical in shape, and the “graduations” marked on it are indicators of the volumes that can easily be measured with that specific cylinder.  Typically, a student’s lab drawer will contain several of these cylinders, spanning a range of possible volumes to be measured.

“Keep eye on meniscus; /
Report results; discuss /
The findings from lab extricated.”

These last three lines sum up the purpose of using a graduated cylinder: measuring a given volume. To do this, a student carefully examines the reading in a graduated cylinder, looking for where the meniscus, the curve created by the liquid in the cylinder, hits the pertinent line on the side of the cylinder.  

(It is always intriguing in writing even these brief essays to come back to the etymologies of some of these terms.  Meniscus is from the Greek for “crescent,” the descriptiveness of which word presumably accounts for its varied presence in multiple disciplinary settings.)

This poem grew out of some idle pondering of a rhyme for an unusual chemistry term, as many of these do.  To make “discuss” plausible as a rhyme for the final two syllables of “meniscus,” this poem describes a common goal in a lab setting. In reporting on the volume measured for a given liquid, a student would “discuss / [t]he findings from lab extricated”: the data they obtained in lab by using their graduated cylinder to complete the week’s procedure.