I Am Your Density

I've given away some test tubes and now for some ideas on how to use them. This is the first of those posts.

Density is a measure of the mass of something for a given volume, or in other words how much stuff is smashed into some space. It has a formula of ρ=m/v where:

ρ = density
m = mass
v = volume

Different materials have different densities. Old home chemistry books encouraged you to run to the drug store and get some mercury, carbon tetrachloride, water, oil, iron, a rubber stopper, and a cork. Pour the liquids in in order and then drop in the solids and you have a seven layer density column. This particular column is now very difficult to recreate because both mercury and carbon tetrachloride are no longer sold at the drug store. Steve Spangler has a great description of another 7 layer column that can be created from things found around the house.

Our set up for today is even easier. We are going to make a four layer column using three sugar solutions and plain water. So start by getting five test tubes and a pipette. Three test tubes will have sugar solutions one will have plain water and the last will be used for making the column. In the first tube put two mL of sugar, one drop of red food coloring, and fill it to the 10mL mark with water. In the second tube place four mL of sugar, one drop of green food coloring, and fill it to the 10mL mark with water. In the third tube add six mL of sugar, a drop of blue food coloring , and fill it to the 10mL mark with water. Lastly, in the fourth tube fill it with water. Now shake them until they are all dissolved. One mL of granulated sugar has a mass of about 0.8 g while one mL of water has a mass of 1 g. So your solutions have densities of:

plain water:(10g H₂O+ 0g sugar)/10 mL =1 g/mL
red: (10g H₂O+ 1.6g sugar)/10 mL =1.16 g/mL
green: (10g H₂O+ 3.2g sugar)/10 mL =1.32 g/mL
blue:(10g H₂O+ 6.4g sugar)/10 mL =1.64 g/mL

Now take a pipette full of the blue solution and add it to the empty fifth test tube. Now take a pipette full of the green solution and add it very carefully to the column. To do this you will need to slowly dribble it down the edge of the test tube. It should form a layer on top of the first one. Now do the same with the red layer and the water layer. It should look something like this.


Amazingly it will stay this way for quite a while. The next picture is the column after 12 hours. You can see that the plain water and the weakest concentration have begun mixing.


They will slowly go on mixing and after a week mine looks like this

You can still see separation between the top two and bottom two layers. After another few days in the window some mold started growing on the top so I washed it down the drain.

Now try playing with the solutions. Can you get them to stack in the wrong order? Can you make a solution dense enough to float a raisin in it? If you make alternating solutions of sugar and salt do they last as long as a column made from just sugar? Do they last longer?

I hope you all enjoy making and playing with your own density columns. Let me know how it goes.

Euclid

Geometry has always been my favorite math class. I always wanted to take a college level geometry class but I've never been able to fit it into my schedule. So I decided to read Euclid's Elements and cover the basics again. I really wanted to see the Greek (I don't read Greek but I wanted to see it) while I read the text in English. Marcelle had read and used the Elements as a text book in her days at St. John's in Santa Fe and I asked her if her text had the Greek. She said that it did not and that as far as she knew an inter-columnar version didn't exist or they would have used it.

I searched on Google and found that in 2007 Richard Fitzpatrick published a completely free and wonderful pdf version of the Elements in both Greek and English along with a Greek-English Lexicon. My plan is to print and bind the book along with blank pages in between the text so that I can work the proofs along with the text. Towards this goal Marcelle bought me a great compass so that I can make it look good to.

While I was searching for information on Euclid I decided that I wanted some old manuscripts of the Elements like this one. So I bought a sheet of papyrus from the local art store and while Marcelle and the kids were visiting her parents I acquired some papyri with parts of the Elements on them. These are pictures of them.

These first two are the definitions from the start of Book 1 "1. A point is that of which there is no part." You can see that this item is a composite of two pieces of papyrus "glued" together to make one larger piece.

This is the end of Proposition 11 from Book 4 inscribing a regular pentagon in a given circle. I haven't decided if I'm going to distress these last two like I did the first one.

This, of course, is the famous start of Proposition 47 from Book 1 proving the Pythagorean Theorem.

Liquid Diet

A few days before Christmas 2003 I had my mouth wired shut after having surgery on my jaw. I was on a liquid diet for a week and then I graduated to things like jello. I am here to tell you that you can only drink so much chicken broth before your body starts screaming "Give me a steak!" and I still gag when I think about drinking Ensure. Remembering this episode got me wondering if it is possible to survive solely on pure chemicals? While searching the literature I found out not only that it is possible but what the perfect recipe is. In a paper entitled "Evaluation of Chemical Diets as Nutrition for Man-in-Space¹" Winitz et al inform us that the perfect diet is:

Amino-acids
l-Lysine·HCl 3.58 g
sodium l-aspartate 6.40 g
l-Leucine 3.83 g
l-Threonine 2.42 g
l-Isoleucine 2.42 g
l-Proline 10.33 g
l-Valine 2.67 g
Glycine 1.67 g
l-Phenylalanine 1.75 g
l-Serine 5.33 g
l-Arginine·HCl 2.58 g
l-Tyrosine ethyl ester·HCl 6.83 g
l-Histidine·HCl·H₂O 1.58 g
l-Tryptophan 0.75 g
l-Methionine 1.75 g
l-Glutamine 9.07 g
l-Alanine 2.58 g
l-Cysteine ethyl ester·HCl 0.92 g

Water-soluble vitamins
Thiamine.HCl 1.00 mg
d-Biotin 0.83 mg
Riboflavin 1.50 mg
Folic acid 1.67 mg
Pyridoxine.HCl 1.67 mg
Ascorbic acid 62.50 mg
Niacinamide 10.00 mg
Cyanocobalamin 1.67 mg
Inositol 0.83 mg
p-Aminobenzoic acid 416.56 mg
d-Calcium pantothenate 8.33 mg
Choline bitartrate 231.25 mg

Salts
Potassium iodide 0.25 mg
Potassium hydroxide 0.83 g
Manganous acetate 18.30 mg
Magnesium oxide 0.38 g
Zinc benzoate 2.82 mg
Sodium chloride 4.77 g
Cupric acetate 2.50 mg
Ferrous gluconate 0.83 g
Sodium glycerophosphate 1.67 mg
Calcium Chloride·2H₂O 2.44 g
Ammonium molybdate·4H₂O 5.23 g
Sodium benzoate 1.00 g

Carbohydrates
Glucose 555.0 g
Glucono-δ-lactone 17.2 g

Fats and fat-soluble vitamins
Ethyl linoeate 2.0 g
α-Tocopherol acetate 57.29 mg
Vitamin A 3.64 mg
Menadione 4.58 mg
Vitamin D 0.057 mg

They point out that these diets are unique because " (a) their essential and nonessential nitrogen is provided in the form of highly pure L-amino-acids; (b) the are administered as single, crystal clear solutions which are nutritionally complete in themselves"

The dry ingredients were dissolved in distilled water to give a solution of 50-75% solids by weight which was completely sterile and had about 2-3cal per mL and could be stored almost indefinitely.

24 inmates from the California Medical Facility volunteered to drink/eat nothing but this liquid diet for 19 weeks. They were allowed to drink as much as they wanted and they could have all the water they wanted too. I can understand why they needed to use inmates because if they were on the outside after a week or so a cheeseburger looks really good.

They found that this diet provided well for these inmates and that there were no ill effects on their health. The authors go on to explain that these diets overcome some of the limitations inherent in alternative space-food sources:

"[These diets provide] high nutritive efficacy in ultra-compact form-1 ft³ of the diet as a 75% solution in water, will provide a 154-lb astronaut with all his required essential and nonessential nitrogen, salts, vitamins, and fats, in addition to his estimated requirement of 2,830 calories per day, for a period of a month; (b) complete water solubility- provides advantages in the administration of the diets in liquid form under conditions that will not permit the use of solids; (c) low bulk reduces low faecal residues and mitigates the critical problem of disposal of solid wastes; (d) complete nutrilite accessibility-allows alteration at will of the amino-acid ratios, carbohydrate content, and levels of all other components, thereby making it possible to tailor formulations to specific dietary needs of individual astronauts; (e) complete digestibility- provides dietary components in the most elemental form in the event of disturbances of the digestive system; (f) good storage stability either in the solid state or as aqueous solution."

This might be worth looking at for food storage...
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¹Winitz, M.; Graff, J.; Gallagher, N.; Narkin, A.; Seedman, D. A.; Nature 1965, 205, 741-743

Dutched Chocolate

My sister recently asked me "Why is cocoa processed with alkali in so many chocolate flavored products?"

First what is alkali processing or dutching? A solution of alkali (a base), usually potassium carbonate, is added to the cocoa nib before roasting. It's also possible to dutch cocoa liqueur or powder. Most of the cocoa liqueur used for making cocoa powder is dutched but the majority of liqueur used for making chocolate is not. Alkalising was developed in the 19th century in the Netherlands by Coenraad Johannes van Houten¹. He was trying to develop a chocolate powder that dissolved better in milk or water. Whether or not dutched cocoa dissolves better is still disputed but what the process definitely does do is change both the color and flavor of the cocoa.

The trick is to add just the right amount of base not too much because too much base will cause the triglycerides found in the cocoa butter to saponify thus giving it a soapy flavor. To avoid these off putting flavors small amounts of ethanoic or tartaric acid added to neutralize the high pH.

Some cocoa nibs are very acidic and the alkalising greatly helps flavor of the final chocolate product. Another thing that the base does is promote the formation of Miallard products (see another great article about how bases catalyze the Miallard reaction here.) Miallard products are those great flavors that form when proteins and sugar react.

The color change in the cocoa is due to reactions of the tannins in the cocoa. Tannins are polyhydroxyphenols, which means they are aromatic compounds (as apposed to an aroma compound) with several alcohol (-OH) groups. In the figure you can see a common one in cocoa, epicatechin. Depending on how the nib is fermented, dried, and roasted the tannins can join together, oxidize, and react with other chemicals in the cocoa to form color-giving molecules. This makes the cocoa much darker in color. By varying the pH, moisture content, and processing conditions it is possible to make cocoa of many different colors.

So when should you use alkali unprocessed cocoa? Well that depends on your leavening agent. Baking soda needs an acid to make it form CO₂ and cause your cake to fluff up nicely. Adding acidic unprocessed cocoa will cause it to rise. Further more, baking soda is a base and if added to the already basic dutched cocoa it can cause the cocoa butter to saponify and give soapy flavors to the dish. But because baking powder is a mixture of an acid and baking soda you want to use dutched cocoa so that it doesn't taste too acidic.

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¹Casparus van Houten, Coenraad's dad, figured out how to easily remove cocoa butter from the nibs enabling the creation of cocoa powder. The nib contains about 54% cocoa butter by weight and this butter makes it difficult to mix into water or milk to make a drink. By pressing the beans, either with a hydraulic press or with a screw press, about half of the butter is expelled from the bean and the cocoa mass that is left can be ground into cocoa powder. This then allowed others to combine cocoa powder and sugar together and then remixing it with some of the cocoa butter thus forming something very close to the of chocolate of today.

DB Lavash and dips.

During this challenge Marcelle asked me to take a turn kneading the dough. A little while later, she gave me some constructive criticism on how I knead dough. It turns out that while I thought that I was kneading the dough, I was really just folding the dough in half and smashing it flat time and time again. What I was not doing was pulling and stretching the gluten molecules into a nicely aligned mass.

Harold McGee informed me that wheat flour is special in the grain family because it is the only grain whose endosperm proteins will interact strongly enough to form a gluten (most simply, a combination of gliadin and glutenin) that will support a raised bread. It is true that some other grains (like rye) will form gluten, but the formed gluten is weak and can't support the raising of the bread. To form a good bread the dough must be both plastic and elastic. Able to stretch out of shape when pressure is applied (plastic) and able to pull back to its original shape after the stress is removed (elastic). If the dough were just plastic, all of the carbon dioxide produced by those hard-working, fermenting yeasts would just flow to the surface and escape, making something very like bricks or hockey pucks. On the other hand, if the dough were completely elastic, the CO₂ would be crammed into a few very pressurized pockets and the bread would come out looking like swiss cheese: a very dense mass with a few pressurized pockets of gas.

Unkneaded gluten is a coiled up protein that you can visualize like a Slinky. Unlike a slinky, the reason gluten stays coiled up is that there are chemical bonds (disulfide bonds) holding the spiral layers together. Kneading stretches the "gluten-Slinky" until those disulfide bonds break. Once stretched the disulfide bonds can reform with other broken disulfide bonds in the new stretched position to keep the gluten all aligned. After reading about kneading gluten doughs I realized that the disulfide breaking and forming is a lot like what is happening during a permanent wave, but this explanation will have to wait for another post. So even with my poor kneading technique the lavash was delicious, the dips were delightful (mostly), and best of all I learned some new chemistry.

I didn't find this project very challenging. My cracker experience is not vast, but I did make whole-wheat saltine/"wheat thin" type crackers once a week for our baby for about 8 months after he started eating solid foods and before I wanted to expose him to long-ingredient-list store-bought crackers. I have made a lot of pita bread--with a variety of outcomes and a ton (almost literally) of pizza dough, so flatbreads are not altogether foreign to me. The recent lavash challenge was fun and easy and made for a nice snack when we had some friends over to play games one evening.

I followed the instructions exactly, but I had a few problems; here they are, in no particular order. Despite using an oven thermometer and switching the lavash from top to bottom rack and front to back partway through baking, one pan was much darker brown than the other. The paler pan also made lavash that were puffed and chewy. I'm sure this has reference mostly to the cheap oven in our rental home, but other bakers I conferred with confirmed my experience. I used sea salt on one pan and poppy seeds on the other, but despite spraying water, 70% of them fell off before they were eaten.

For the toppings, we decided to try to the Tahitian almond spread recipe provided and also made a basic pico de gallo (tomatoes from our garden, onion, serrano chile, cilantro, salt). I also served some olivada (see Moosewood Restaurant Cooks at Home) I had made with green olives a few days before. The olivada is a long-time favorite and the pico disappeared quickly; when all the chunks had been dipped out of the bowl, the juices were very nearly drunk by our friend. The almond spread was a little weird. I love almond butter and eat it almost every day on toast for either breakfast or on an apple for a maternity snack, but putting it with garlic, cilantro, honey, orange juice and pine nuts did nothing to further endear me to a food I already enjoy as it is. I'm really looking forward to next month.

Daring Bakers

Marcelle and I have joined a great group called the Daring Bakers. Each month they send out a recipe that everyone is to follow and then on a given day everyone posts their results on the same day. August was our first month with the group and we made éclairs. We made a hazelnut cream filling with a chocolate toping. To quote our toddler son they were "DEElishush."


This, however, is a blog about science, so I want to talk about the science behind éclairs. The dough is very simple to make. First water, butter, and milk are brought to a boil, then flour is stirred in all at once. The dough that forms is stirred and cooked for a few minutes on the stove to swell the starch. Then you transfer the dough to a mixer bowl and eggs are beaten in, one at a time. The dough is piped onto cookie sheets and baked in a hot oven.

You notice that there is no chemical leavening agent included in the dough, such as yeast or baking soda, and yet it forms lots of wonderful air pockets during baking. How does this happen? Steam forms as the puffs bake and the strong gluten structure formed by beating the dough stretches to hold the steam. With the steam trapped, the heat then coagulates the gluten and egg proteins forming a rigid wall that will hold its shape. If done properly, the puffs will be golden brown, with a hollow center crisscrossed by a soft network of dough filaments.

Each ingredient plays a part in making a good puff. First the water, milk, and butter need to be boiling so that when the flour is added it will swell (hydrate) the starch granules and gluten (gluten is made up of two proteins gliadin and glutenin). The more butter you add, the more tender the cream puff will be, but if you have too much it will interfere with the gluten stretching and the cream puff will collapse.

The eggs that are beaten into the dough act as the leavening agent. The yolks add fat and act as an emulsifier for a smooth and even texture in the finished product. Egg proteins add to the structure of the cream puff as it cooks.

Baking any dough is a delicate dance between two processes: the expanding of gas and the coagulation of gluten and gelatinization of starch. If the oven temperature is too low, the trapped air will expand and escape before the gluten and starch have set. The puff will collapse and be a tough mass. Also, the puffs depend on steam production to cause the to rise: if the temperature is too low there won't be enough steam to cause the puff to rise, and if the temperature is too high, the proteins and starch will set and brown before the gas has expanded to its full size. This will again lead to unpuffed puffs.


This recipe was an exciting start to our membership in the Daring Bakers Club. I felt like many of the components were unnecessarily complicated--for example, the best glaze for eclairs I've ever tasted (and had great success with) is a simple 5/4 chocolate/cream ganache. It doesn't get any easier than making it in the microwave. The glaze recipe we were instructed to follow to the letter never set up, not even after time spent in the cool of our freezer for a while. It included silly component recipes (which tasted great as ice cream toppings) but did nothing to further our desire to repeat this recipe experience. The choux recipe chosen for us by this month's host was a good one, although many important instructions were omitted from the instructions--like how wide the puffs should have been in addition to how long, and whether they should cool on racks or on sheets or on parchment paper pulled off the sheets and placed on a counter/table. Dave complained that it seemed like this recipe was intended to dirty as many dishes as possible, and because he is our "dishwasher," he should know. We thought the double chocolate hit from the pastry cream and the glaze would be too much (even for confirmed chocolate lovers), so we opted for a hazelnut pastry cream that we created from our vast store of experience making hazelnut gelato and it turned out really nice. We WILL be making that part again. All in all, this was supposed to get us cooking together in the kitchen, which happened three nights in a row this week for us to get all our components together. So, in that way, despite my quibbling, it was an unqualified success! ---Dave's lab assistant

Chinese Chemistry

I really enjoy looking at the Periodic Table. I love the amount of information that is available in such a condensed form. I like the Table so much that I carry one in my wallet. There is one in the kitchen (in English) and one in the bathroom (in Spanish). As I was thinking about the periodic table I began to wonder what it looks like in Chinese. It just so happens that I work with a couple of Chinese guys so I asked them to show me a Chinese periodic table. I noticed right off that all of the Nobel gases had one shape in common throughout the family. Then I noticed that it wasn't just the Nobel gases but all of the gases had the same character. Then I noticed that the metals had another character and last the non-metal solids another character. My labmate explained that in Chinese the majority if the symbols are made up from two parts. The first part (the radical) tells you what the physical state of the element is at STP. The second part is phonetic and tells you how to pronounce the symbol.

I learned (after installing the East Asian languages on my computer) that there are four radicals used on the periodic table and they were the shapes I had noticed at the beginning. They are 金or 钅(literally "gold" for metal), 石 (literally "stone" for non-metal and metaloid solids), 水 or 氵 (literally "water" for liquids), and 气 (literally "air" for gases). The phonetic part is based on the western name of the element. Below you can see some examples of this radical phonetic symbol pairing.


Here "metal" and the phonetic "bi" combine to form bismuth.


"Metal" plus "nei" form "na" for natrium or sodium in English. I like this one because it shows that they aren't just using the English pronunciations of the elements.

"Stone" and "dian" form iodine.


"Air" combines with "fu" to make fluorine.

There is set class of symbols which are for elements that were known since ancient times. Elements which were known to the Chinese alchemists like gold, iron, sulfur, and mercury. I especially enjoy the symbols for iron and sulfur. Iron can be broken up into several parts.


Which could be interpreted "metal from the mountain for making weapons." Sulfur can be broken apart to show that it is a stone that flows.


Lastly there are some characters that are descriptive of the element that they represent. Examples are phosphorus and bromine. Phosphorous breaks down to "the stone that glows" and bromine is the "stinky liquid."



Some of the websites that I found especially useful are Zhongwen, a website about Chinese characters and their etymology, the Wikipedia entry on the chemical elements in East Asian languages, and an IUPAC article on the Chinese terms for chemical elements.

Chemistry or Star Wars?

Fireflies

Two of the things I miss most from Ohio are fireflies and thunderstorms. I miss seeing the fireflies flashing out their seductive Morse code on a warm summer evening and I miss the ominous clouds, rushing wind, huge warm rain drops, flashing lightning and crashing thunder, and maybe most of all the smell right after a midsummer thunderstorm. So with these thoughts on my mind I decided to find out how a firefly produces light. I found some great cites and books to talk me through the process.

Lets first look at the structures. Shown below are firefly luciferin, luciferyl adenylate (luciferin attached to AMP), and oxyluciferin.

Another major player in the light emission from fireflies is the luciferase enzyme which mediates the entire set of reactions. The basic mechanism is as follows:

1. Luciferin and ATP react to form luciferyl adenylate and inorganic phosphate (PPi)
2. Luciferyl adenylate reacts with oxygen to form oxyluciferin*, CO₂, and AMP (the * indicates an excited electronic state)
3. The excited oxyluciferin* rapidly loses a photon of visible light as it goes to its electronic ground state.
4. Ground state oxyluciferin is then regenerated into luciferin through a number of different steps.

This is summerized in the figure below.



For a more detailed explanation see Dr. Branchini's page on firefly bioluminescence, including information on the luciferase enzyme.

Periodic Table of Videos

This is a fun website put out by the University of Nottingham that tells a little bit about the elements on the periodic table. Some of my favorites are Na, P, He, and F.

Cogito Ergo Boom II

Last summer I heard about Summer Explosives Camp and I thought to myself what was I doing all those years at EFY? Then I learned that it hadn't been available when I was eligible and I felt a little better.

When I was at ISU I had an opportunity to go and see the research and development facilities at Thiokol. It was amazing. They talked to us about ammonium perchlorate (NH₄ClO₄) which is the oxidant that they use for the solid fuel rocket boosters. Because it is water soluble they need to be careful about getting it on their clothing because it will be soaked up and then it will dry in the clothing making the clothes very dangerous. To demonstrate they had a leather boot that they had soaked in a saturated solution for several days. They then allowed the boot to dry thus trapping all of the ammonium perchlorate in the leather. Next they lit the boot on fire starting at the toe. At first it didn't seem like much was happening and then a flame about 4 feet tall shot out of the leg of the boot and consumed the boot. After a few seconds all that was left was the steel toe of the boot. It was very impressive. They stressed to us that rocket fuel isn't explosive. You don't want an explosive fuel. You want a fuel that burns at a steady rate and extremely reproducible.

As we were entering a building they had us look out over the facilities and pointed out a two rows of buildings. They were evenly spaced identical buildings with one lot empty. Our guide told us that that was where a fire had broken out while they were mixing the fuel and the building was destroyed. At that point I decided that as cool as it would be to work with high energy materials, it was more important to come home every night.

So on to explosives. How can you predict how much energy will be released from a chemical explosion? That is a very difficult question and one that we still can't predict perfectly. There are a few rules of thumb that can get us to within about 10%-20% of the answer. The first step is to know the structure of the explosive. I've shown some common ones below.


Once you have the structures you can calculate the oxygen balance. When an explosion takes place the explosive molecule breaks apart into its individual atomic constituents. These quickly form several small stable molecules including H₂O, CO₂, N₂, H₂, CO, etc.

By considering the formulas of the explosives and determining how much oxygen is in the molecule compared with how much oxygen is needed to completely oxidize the fuel present. If there isn't enough oxygen it is called a negative oxygen balance, like TNT. If there is more oxygen than is needed it has a positive oxygen balance, like nitroglycerine.

There are tables that list the oxygen balance of different molecules and mixtures but it's easy to do even if you don't have a table. It's easy to determine the oxygen balance if you know the molecular formula.

When detonation of HMX takes place the explosive molecule is broken apart and oxidized to form gaseous products. To figure out the oxygen balance we need to assume that the explosive is completely oxidized to form carbon dioxide, water, and nitrogen.

C₄H₈N₈O₈ → xCO₂ + yH₂O + zN₂

Now we need to balance equation. Let's start with the C,

C₄H₈N₈O₈ → 4CO₂ + yH₂O + zN₂

next we do the H,

C₄H₈N₈O₈ → 4CO₂ + 4H₂O + zN₂

now the N,

C₄H₈N₈O₈ → 4CO₂ + 4H₂O + 4N₂

last the O. There are several ways to balance the oxygen but we are going to do it by subtracting O₂ from the right side of the equation.

C₄H₈N₈O₈ → 4CO₂ + 4H₂O + 4N₂ - 2O₂

In order to balance the the formula we had to put a negative sign in front of the O₂. That indicates a negative balance, meaning that it takes more oxygen than the HMX has to fully be oxidized to water and carbon dioxide.

This amount of oxygen as a weight percent of the total molecule can be calculated by taking the mass of the oxygen on the right side of the equation, -64¹ and dividing it by the molecular weight of HMX, 296² all times 100%. (-64/296)∗100%=-21.6%.

The oxygen balance doesn't tell us the how much energy will be released from a given molecule or mixture but the strength, brisance, and sensitivity of an explosive or mixture are seem to increase as the oxygen balance approaches zero.

Zero oxygen balance also leads to fewer toxic gases released during the explosion. If the oxygen balance is negative CO is formed. If the oxygen balance is high NOx (NO + NO2) is formed. While this isn't a problem if detonating in open air with good ventilation, it is a problem in mines with poor ventilation.

So we haven't gotten to the part where we predict how much energy comes from a given explosive but this is enough for this post and the rest will just have to wait.

For more information on the chemistry of explosives see:

Akhavan, Jacqueline. The Chemistry of Explosives. RSC paperbacks. Cambridge, UK: Royal Society of Chemistry, 2004.
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1. Take the molecular weight of O₂ and multiply by the number of moles added to the right side = 32∗-2 = -64
2. 4C+8H+8N+8O = 4∗12+8∗1+8∗14+8∗16=296

LOx

Today I'll be talking about an important part of all combustion, oxygen. I decided to condense some oxygen and see what I could burn. To condense the oxygen I put a glass tube in some liquid nitrogen and started blowing oxygen into the tube. The boiling point of nitrogen is 77.36 K while the boiling point of oxygen is 90.2 K so the oxygen readily condenses in the glass. I then poured the lovely blue liquid oxygen onto some cotton and set it on fire. What you see below is what followed. Notice that there is no black charred cotton at the end.



Cotton is primarily cellulose so the chemical reaction for what is happening is:

(C₆H₁₀O₅)_n + n (6O₂) --> n(6CO₂ + 5H₂O)

There is no leftover charred cotton because I had an excess of O₂ the reaction went to completion turning all of the cotton into CO₂.

Cogito Ergo Boom

I was walking home from school one day thinking about explosives and I overheard someone say cogito ergo sum. My brain interpreted this as Cogito Ergo Boom. I knew that I couldn't have been the first to come up with the phrase and I was right. But that won't stop me from using it.

For my next few posts I though that I'd talk a little about explosives. There are three main types of explosives: mechanical, chemical, and atomic. We'll start with mechanical explosives.

Mechanical explosions occur due to a physical change in the system. Examples of mechanical explosions are pipes freezing in the winter, dry ice bombs, popping balloons, and the heating of a whole egg in a microwave. In each of these pressure is built up in side of a closed system. Ice expands by about 10% in volume compared to the unfrozen water causing the pipes to burst.

The CO₂ in the dry ice bomb goes from 1.5g/cm^3 to 0.044g/cm^3 at STP. So while the 40 grams of dry ice that go into the 1 L bottle only take up 26 cm^3 once it all sublimes it will take up 224,000 cm^3 at STP.

While these are impressive displays of mechanical explosions the largest mechanical explosion to ever occur was the explosion of Krakatoa. The explosion of Krakatoa was equivalent to 200 megatons of TNT. For scale purposes the largest bomb that the US stockpiles is the Mk-B53 at 9 megatons. The bomb Little Boy, dropped on Hirosima, was about 13 kilotons or 13,000 times weaker than the explosion at Krakatoa. The largest bomb ever detonated was only 25% of Krakatoa. There are reports of people hearing the explosion over 3,000 miles away. It is the loudest sound in recorded history.

So while mechanical explosions are as easy to make as popping a balloon they are also the most powerful explosions know to man.

Temper Temper

To make chocolate look good, with a high gloss, and have a good snap it must be tempered. Tempering chocolate ensures that all the fat in the chocolate sets in the correct crystalline form.

To understand tempering we must first understand the structure of fat. The vast majority of the fats in chocolate are triglycerides. A triglyceride is a class of fats made up of glycerol linked to three fatty acids. Furthermore, three main fatty acids account for about 95% of the fat present. These three fatty acids are oleic acid (35%), stearic acid (34%), and palmitic acid (26%). Stearic and palmitic acid are saturated fatty acids, meaning all of the carbon atoms are saturated with hydrogen, while oleic acid is a monounsaturated fatty acid, there is one double bond which could be hydrogenated.
Fatty acids are called fatty acids because they have a long aliphatic carbon chain with an acidic carboxylic acid group at one end.

This diagram shows one of the ways these fatty acids are attached to the glycerol. Shown here is what is known as a SOP triglyceride because it has stearic acid attached to the first glycerol carbon, oleic acid in the middle, and palmitic acid in the third position. If we were to switch the oleic and stearic acids it would be a very different molecule.

As I said earlier stearic and palmitic acids are saturated while pleic acid is unsaturated. So our triglyceride is one of a subset of triglycerides found in cocoa butter known as SOS triglycerides. This set of triglycerides has oleic acid sandwiched in between two saturated triglycerides. SOS triglycerides make up 80% of the fat in cocoa butter. Because the fats in cocoa butter are primarily SOS triglycerides they melt over a short temperature range (room temp to body temp).

Cocoa butter is polymorphic which means that it can crystallize in multiple arrangements. Carbon is also polymorphic, it can be a diamond, graphite, or a bucky ball. While carbon has three polymorphs cocoa butter has six. These six forms were named by two different groups in the same year (1966). The chocolate industry uses Roman numerals I-VI as described by Willie and Lutton, while the oils and fats people prefer using Greek letters with superscripts and subscripts as set forth by Larsson (γ, α, β'₂, β'₁, β₂, β₁).

Form I (γ) melts from 61° to 67° F

Form II (α) melts from 70° to 72° F

Form III (β'₂) melts from 78° to 80° F

Form IV (β'₁) melts from 81° to 84° F

Form V (β₂)melts from 93° to 95° F

Form VI (β₁) melts above 97° F

Only one of these six polymorphs (form V) forms the shiny, firm chocolate that gives the nice snap when broken that we like. If we want to enrobe a truffle or a strawberry with chocolate and we want it to snap when we bite into it we need the chocolate to be in form V. Luckily chocolate comes from the factory in form V. If we can keep it there we will have lovely chocolates. Therefore our goal when we melt the chocolate is to never heat it above 91°-92° F.

Most chocolate melts between 89° -91° F even though all of the form V won't melt until you heat it above 95° F. Between 91° -95° F the chocolate still contains some form V microcrystals of cocoa butter. If you let the chocolate harden around these seed microcrystals it will all form form V chocolate.

If however you completely melt all of the precious form V crystals you need to start over by completely melting all of the chocolate. Be careful not to burn or separate the chocolate by heating it too high.

Next you should cool the chocolate rapidly to about 80° F and always use constant stirring. Cooling this low does allow some of the form III and IV crystals to form, but it gets a good start on the crystallization of the highly prized form V crystals. Now gently warm the chocolate to 86° F. This start the will start to melt the form III and IV so it should be held at this temperature for a few minutes, then warmed up to 91° to 92° F . This will finish melting all of the form III and IV crystals that were formed while cooling.

You can now test the chocolate to see if it is in temper by spreading a smear out on a piece of waxed paper, if it dries shiny and hard within 5 minutes your chocolate is tempered. Now that you have tempered chocolate you should eat it and enjoy. Just be careful about bloom (we'll get to that next time).

Seven Basic SI Units

There are seven basic SI units: the meter, second, ampere, kelvin, mole, candela, and kilogram. Of those seven only the kilogram is still defined by a man made object with no referent in nature. This means that in a vault outside of Paris there is a platinum and iridium cylinder (seen below nested in three glass jars) that cannot gain or lose mass. If you could get past security and cut off a small chunk it wouldn't have lost any mass at all. That's because it defines the kg. All masses are referenced to it. In 1889, 40 copies of this cylinder were made for national standards institutions around the world. These standards have all changed mass in different ways over the years; mass gain through dust accumulation or mass loss through cleaning. And although they can compare the copies with the original with an accuracy of better than 10^-9 kg it is still not good enough because thy don't know how the standard has changed. This therefore has led to groups trying to define the kilogram with a universally verifiable standard.

Two major approaches are being followed: atom counting and electrical approaches. The atom counting approach is easy enough to understand-count every atom in a sample then multiply by the mass of the atom and then you have the mass of the entire sample. Unfortunately we can't do this yet. What we can do is grow very pure crystals. The leader in the atom counting field is the Avogadro Project. They are seeking to make a single crystal silicon sphere, using laser interferometry to measure the diameter and then because they know the crystal structure of silicon they can calculate the number of atoms in that sphere.

Why use silicon? Because technology has been developed to purify silicon to a higher purity than anything we can make. Silicon used in the semiconductor industry is >99.99999% pure. It is made through a multi-step process first with zone refining and then a single crystal boule is grown from pure molten silicon. The isotopic make-up is then measured with a mass spectrometer and average atomic mass is then calculated. This single cryastal is then cut and polished into a perfect sphere. Alright it isn't perfect but it is nigh-perfect. To quote Wikipedia:

On the Ø 93.6 mm sphere, an out-of-roundness of 35 nm (undulations of ±17.5 nm) is a fractional roundness (∆r/r) = 3.7 × 10^–7. Scaled to the size of Earth, this is equivalent to a maximum deviation from sea level of only 2.4 meters. The roundness of that ACPO sphere is exceeded only by two of the four fused-quartz gyroscope rotors flown on Gravity Probe B, which were manufactured in the late 1990s and given their final figure at the W.W. Hansen Experimental Physics Lab at Stanford University.

The problems that they are facing are things like too much variation in the isotopes of the silicon and the thickness of the silicon oxide layer that grows on the sphere.

The second proposed method for redefining the kilogram is called the electronic kilogram. The idea is to design an incredibly sensitive balance that matches the weight of an object (the force exerted on an object by gravity) to an electromagnetic force produced by a coil of current carrying wire in a strong magnetic field. Then you could define the kg as 'the mass that can be suspended by the electromagnetic force generated when a specific amount of current flows.' So far the electronic kilogram has produced better results than the atom counting method, but it still can't provide an accuracy of a millionth of one percent every time.


1. Robinson, Andrew. The Story of Measurement. London: Thames & Hudson, 2007.

What does that number really mean?

I have found that in science we often use really big or really small numbers but we don't often relate that to something we intuitively know or have experienced. So I'm going to be putting out numbers and what they "really" mean.

I'll start by talking about how much energy the US uses. According to the Department of Energy's report on the Energy Consumption of the US in 2006 we used 99.8 quadrillion BTUs (or as the energy industry says "Quads") of energy. Our usage for the first 9 months of 2007 projected a usage of over 100 Quads by the end of the year. Let's first define our terms.

1 quadrillion = 1x10¹⁵

1 BTU = British Thermal Unit = energy needed to raise 1 pound of water 1 degree Fahrenheit.

So let's now see what we can do with these numbers. While we only get about 22.7% of our energy from coal (22.8 Quads) If you wanted to haul all of this coal in one train it would have 11 million cars and be 104,000 miles long. This train would be long enough to go around the world a little over 4 times. And that's just in one year.

Iron Hexacyanoferrate: The Blueprint for Fun

It's Christmas break and while I don't really stop doing research I feel a little justified in taking a little time for myself. Today I decided to make blueprints and cyanotypes. What, you may ask, do blueprints and cyanotypes have in common? The answer is Prussian Blue (PB). We'll get into the chemistry of PB later, but first I'll show you what I made.

Several months ago I found this image on the web and I decided that it would be my first attempt. I chose it for two reasons:

1. It's only black and white, no grey scale, so I'm not going to need to worry about over developing it.


2. I thought that the steampunk image would be appropriate for a process that was developed in the 19th century.

To make this image I took a solution of iron amonium citrate and potassium ferricyanide and coated a piece of paper with it. I then let it dry in the dark. The coated area looked yellow green. I then printed the image on a transparency and taped the coated paper to the back of the transarancy. I then taped the paper and transparancy to the window in my office. After 12 minutes I had noticed that the yellow green color had darkened to a more brown color. I then took the transparency off the window, removed the paper and ran it under deionized water to wash off all of the unreacted chemicals. It is at this point where the blue color really developed. Encouraged by the positive results I decided to make a second harder image.

The second image I made was a little more complex for a few reasons:

1. It is a grey scale image and so I needed to worry about contrast in the image.


2. I needed to make a negative of the picture I wanted to reproduce.


3. The sun went behind a cloud and so my previous time calculations wouldn't work.

As you can see this image is much more pale than the first. But over all I consider it a resounding success.

I said earlier in the post that I used a solution of iron ammonium citrate and potassium ferricyanide to make the light sensitive solution. The actual solutions are 0.95 M Fe(NH₃)C₆H₈O₇ and 0.30 M K₃[Fe(CN))₆]. If you count the electrons in the compounds you will notice that the iron in both the Fe(NH₃)C₆H₈O₇ and K₃[Fe(CN))₆] is in a +3 oxidation state (this can be indicated by superscripted roman numerals K₃[Fe^III(CN))₆]). Once mixed, the light sensitive Fe(NH₃)C₆H₈O₇ absorbs a photon causing an electron to be transfered to the iron atom reducing it to Fe⁺². This ferrous (Fe^II) ion then reacts with the hexacyanoferrate (Fe^III) to form the insoluable Prussian Blue:

K⁺(aq) + Fe⁺²(aq) + >[Fe^III(CN)₆]^-3(aq) ---> KFe^III[Fe^II(CN)₆](s)

If you look at the oxidation states you can see that there was an electron transfer between the hexacyanoferrate anion ion and the ferrous cation. Interestingly for years people thought that they were making the KFe^II[Fe^III(CN)₆] salt which they called Turnbull's blue but which recently has been shown to spontaneously transfer an electron and form Prussian Blue. Prussian Blue comes in two closely related forms that are termed "soluble" and "insoluble". Soluble Prussian Blue has the form of MFe[Fe(CN)₆] where M is a monovalent cation, while insoluble Prussian Blue has the form Fe₄[Fe(CN)₆]₃. In both cases there is an Fe^III cation bound to an [Fe^II(CN))₆]^-4 anion. These names are somewhat misleading because both materials are very insoluble in water however the soluble Prussian Blue can be suspended in water making it look like it has dissolved while it is still just a suspension.

The crystal structures for Prussian Blue is shown below where the Fe^II is shown in red and the Fe^III in blue. The potassium ions sit in four of the eight octants arranged tetrahedrally.

For more information see Day's "Molecules into materials case studies in materials chemistry -- mixed valency, magnetism and superconductivity" page 190, or "A Blueprint for Conserving Cyanotypes" by Mike Ware.

Calvin Chemistry

My reactions didn't go as I had wanted one day and so to blow off a little steam I doctored this Calvin and Hobbes strip originally published on 03/06/91. My appologies to Mr. Bill Waterson.

Phi: A whole H of a lot cooler than Pi

Warning: This post contains no chemistry. Now with that off my chest I wanted to share something that I just discovered all on my own (That's not to say it wasn't known before I discovered it it just means that no one showed it to me.)

I want to make an original tessellation like M.C. Escher's. I then started sketching different regular polygons that can tessellate a plane. When I got to the pentagon I knew that it couldn't tessellate alone but I didn't have a good idea of what else I needed to make it work. So I started drawing pentagons. The first thing I drew looked like this:

I thought "Oh, it makes another pentagon. I could turn this into a fractal" and so I did and I made this:

I then wanted to know what fraction of the area of the large pentagon is taken up by the smaller pentagons. My train of thought went something like this: To do this I needed to find the length of the side of the new large pentagon. That's 2 times the first pentagon plus the space in between. The space in between is the leg of a triangle. The angle of the triangle is 36^o so half of it is 18^o. So sin 18 is 0.309, double it so that's 0.618. WAIT! If I add that to the one of the pentagon's sides that is 1.618 that is the Golden Ratio!

So, after looking on line all of these things were known before I started but I had fun discovering them.

Remember Remember...

Remember, remember the Fifth of November,
The Gunpowder Treason and Plot,
I know of no reason
Why Gunpowder Treason
Should ever be forgot.
Guy Fawkes, Guy Fawkes, t'was his intent
To blow up King and Parli'ment.
Three-score barrels of powder below
To prove old England's overthrow;
By God's providence he was catch'd
With a dark lantern and burning match.
Holloa boys, holloa boys, let the bells ring.
Holloa boys, holloa boys, God save the King!

Happy Guy Fawkes Day! I thought that today would be a great day to discuss gunpowder. From a very early age I knew that gunpowder was made from three things: Carbon, Sulfur, and Saltpetre. I knew what carbon and sulfur were but all I knew about saltpetre was that it came from bat guano. This did not stop me from sharing my vast knowledge of gun powder with my other geek friends "If only we had some carbon, sulfur, and saltpetre we this wall wouldn't pose any problems..."

I continued to dream about making my own gunpowder through my undergraduate time but I never made any even though I had access to all the chemicals. Many of my professors were happy to give me different chemicals for my own projects but I made a decision that I would never use any of the chemicals from school to make explosives. That way if something went wrong the school couldn't be held accountable in any way. During this time however I learned a lot about how gunpowder works. Carbon is the primary fuel in the reaction, sulfur is also a fuel but it also reduces the ignition temperature and speeds us the reaction, saltpetre is also known as potassium nitrate KNO₃ and provides the reaction with the oxygen it needs. A very simplified chemical reaction for the combustion of gunpowder is:

KNO₃ + 3 S + 8 C → 2 K₂CO₃ + 3 K₂SO₄ + 6 CO₂ + 5 N₂

We start with 8 moles of solids and end up with 5 moles of solids and 11 moles of gasses. While the solids take up very little room (a few cubic centimeters at most in a firework) the each mole of gas takes up 22.4 L of volume at stp. It is the rapid evolution of all of these gasses that causes an explosion.

My desire to make gunpowder went from dream to reality when I was at our local pharmacy picking up a prescription. While waiting I was perusing the shelves of vitamins and supplements (I always do this when I have the time because it's good to know what chemicals are available if I need them) I found a bottle labeled "Flowers of Sulfur" and then right next to it from the same company "Saltpetre." It had to be a sign. I bought both bottles and the pharmacist didn't even bat an eye. When I brought both of them home and explained it to my wife she was very understanding and asked me not to blow up our house or our son.

So with these ground rules I got down to business. I had two of the three and all I was missing was the carbon. I called all of the local pharmacies and apothecaries but none of them had any activated charcoal. So I set out to make my own. I knew that the best form of charcoal to use was from softwood charcoal but all I had was newspaper so I burned it and collected the ashes. I weighed out the ashes and used them as my limiting reagent. I weighed out the appropriate amounts of KNO₃ and S to make gunpowder (75% KNO₃, 15% C, 10% S). I put it all into the mortar my mother-in-law gave me and set about grinding it until it was a fine grey powder. I had done it, I had made my own gunpowder. To test it I put a little trail on the ground and I lit it. It burned wonderfully.

So while King James I and Parliament have nothing to fear from me there are some pumpkins around who might.

Edit 11/06: I made this video of burning Guy Fawkes in effigy last night using some of my gunpowder. I also made the wick which isn't very good.

Mole Day

Happy Mole Day everyone!

Atomic Mouse Traps

I'm a TA for a freshman seminar called "Beyond Fossil Fuels" in which we discuss energy and sources of energy. It is my job to come up with an interesting demonstration to illustrate the concept we are studying that day. Today we talked about atomic energy. I decided to use a demo that I had seen on Mr. Wizard years ago: The Mouse Trap Bomb. The story goes that this demo was developed by Walt Disney in the 40's to educate the public on how an atomic bomb works by demonstrating an atomic reaction. I don't know if this is true but I have found some journal articles from the American Journal of Physics that I thought were useful:

1. Sutton, R. M., American Journal of Physics, 1947, 15, 427-428
2. Manley, J. H., American Journal of Physics, 1948, 16, 119-120
3. H. D. Rathergeber, American Journal of Physics, 1963, 31, 62

This demo loosely represents what happens during nuclear fission. The mouse traps represent fissionable atoms while the ping pong balls represent neutrons. When a free neutron (ping pong ball) encounters a fissionable atom (mouse trap with ping pong ball) it induces fission and releases more neutrons (ping pong balls).

This video is the result of several hours of setting up traps and having them go off at all the wrong times.




Ideally the traps would be fixed to the surface so that only ping pong balls would set off other traps. As these traps went off not only did we record video but we also made a separate audio recording. It can be seen here plotted from the .wav file in Mathematica.

We next recorded one trap going off which was then plotted in the same manner. In theory the many mouse trap explosion could be recreated by taking linear combinations of the single mouse trap and overlapping as time goes by.

Using those two data sets and Mathematica's awesome computing skills we checked to see if we could plot the number of traps firing vs time. To do this we did a correlation between the two data sets to shows the degree to which the two data sets are linearly related. The plot below shows the amount of correlation (the number of traps firing) vs time.

As you can see the rate at which the traps are firing increases rapidly and then dies off. This is very different from a normal chemical reaction (A+B-->C+D where A and B are reactants and C and D are products) . The rate of a chemical reaction is proportional to the concentration of the reactants. The reaction is fastest the instant the chemicals are mixed and slows down over time because the reactants are consumed over time and their concentration falls. The fission reaction of can be written as follows A+B --> C+D+2A. Where A is a neutron, B is a fissionable atom, C and D are the products of the split atom B. So the reaction produces starting material exponentially. The reaction dies off because we are using up B.

So while we may just enjoy the demo because we like seeing ping pong balls fly across the room, there is so much more we can see in it. And that's what makes it a great demo.

Buttermilk Syrup

Before I started dating Marcelle she invited my friend and I over to have breakfast. She made waffles and buttermilk syrup. This is one of the best additions to breakfast since John and Will Kellogg started making cold cereal (and from me that's saying a lot!) After several large servings my friend suggested hooking the syrup up as an IV so that he could get it into his system faster. Not only is this syrup one of the most delicious confectionery concoctions (suitable to be eaten on just about anything), but it also is a great display of a multitude of kitchen chemistry phenomenon. I've now gotten ahead of myself, here is the recipe:

• 1 stick butter


• 1 cup sugar 1/2 cup buttermilk


• 1 tsp. vanilla


• pinch of salt


• 1 tsp. baking soda

Put the butter, sugar, salt, and buttermilk into your pan and just barely bring it to a boil. Take it off the heat and add the vanilla. While still warm and just before serving add the baking soda and stir, this will cause the syrup to foam and almost triple in volume (make sure there is room in your pan for this to happen). Now pour liberally over pancakes, waffles, and french toast. Also try it in combination with peanut butter and/or bananas, strawberries, and melon. Marcelle's favorite way to have it is on waffles with with fresh berries. The berries go in each little square and then you fill the rest of the square with the syrup. Yum!

Buttermilk syrup foams for the same reasons that baking soda and vinegar make fun volcano's, except the acetic acid has been replaced by lactic acid.

The first step is the protonation of the bicarbonate (HCO₃^- ) to form carbonic acid (H₂CO₃). Carbonic acid is in equilibrium with carbon dioxide and water as seen by the following reaction.

The equilibrium constant (k₁/k_-1)in this reaction explains why the CO₂ evolves rapidly. The rate constant for the forward reaction, k₁, is 23 s^-1. The rate constant for the reverse reaction, k_-1, is 0.039 s^-1. So the equilibrium constant (k₁/k_-1) in this reaction is ≈590 which lies heavily in favor of the products.

Now go and make your own kitchen chemistry marvel.

Liquid Nitrogen Pumpkin Ice Cream

Here is one of our latest kitchen chemistry adventures: Liquid Nitrogen Pumpkin Ice Cream. First the list of ingredients:

• 3/4 c. brown sugar


• 1 c. canned solid-pack unsweetened pumpkin


• 1 tsp. cinnamon


• 3 egg yolks


• 1/4 c. granulated sugar


• 1/4 tsp. grated nutmeg


• 1/8 tsp. ground cloves (this was a little too much for me)


• 1/2 tsp. ground ginger


• 2 c. heavy cream


• 2 c. milk


• 1/8 tsp. salt


• 1 tbsp. vanilla extract

Combine cream, milk, brown sugar and granulated sugar in a medium-sized saucepan over medium heat. Cook, stirring, until the mixture is hot but not boiling, about six minutes.

Whisk eggs in a medium bowl. Gradually whisk 1 c. of the warm cream mixture into the bowl with the eggs.

Pour the egg mixture back into the saucepan, reduce the heat to medium-low, and cook, stirring, until the mixture thickens enough to coat the back of a spoon, 5 to 10 minutes. Do not boil.

Strain the custard into another bowl and cover it partially with plastic wrap. Cool at least one hour at room temperature.

Combine pumpkin, vanilla, cinnamon, ginger, nutmeg, cloves and salt in a medium bowl and blend well. Add to the cooled custard and mix so that all the ingredients are evenly distributed. Refrigerate, covered completely, in the coldest part of your refrigerator until the mixture is very cold, about six hours.

Stir the cold pumpkin mixture, then pour into the mixing bowl of an ice cream maker. Freeze according to ice cream maker manufacturer's directions.

Put pumpkin ice cream in a container with a tight cover. Freeze at least three hours before serving.

Some helpful hints:

When thickening the custard so that it coats the back of a spoon (step 3), the temperature of the mixture should register at least 160 degrees F on a candy thermometer.

The refrigerated custard that has yet to be frozen in the ice cream maker (step 5) can stay covered in the refrigerator as long as three days.

The finished pumpkin ice cream tastes best if eaten within four days of making it.

When heating the custard in the thickening phase (step 3), do not boil it. The egg yolks will curdle.

Now for the cool part. Instead of making the ice cream in your ordinary every day ice cream maker we used N₂(l). Nitrogen makes up 78.1% of the air we breath and is completely harmless. When it is cooled to 77K (-195.79 °C, -320.42 °F) it becomes a liquid. We bought our N₂ from the chemistry department for $1 per liter. If you don't have a chemistry department handy you can purchase it from AirGas (my local store sells it for $2/L but you need a DOT approved container) Next we dumped the N₂ into the chilled custard and watched it harden into ice cream.

There are several videos of people doing this on YouTube so you can see how it's done. The Guinness Book of World Records says that the current record for making one L of ice cream is 18.78 seconds held by polymer physicist Peter Barham from the University of Bristol, UK.

Maybe I'll go for the record.