Oct 232016
 

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Today is Mole Day, an unofficial holiday celebrated among chemists, chemistry students and chemistry enthusiasts on October 23, between 6:02 AM and 6:02 PM. No, it does not celebrate pesky little furry mammals who make hills that some people make into mountains. The mole is the unit of measurement in the International System of Units (SI) for the amount of a substance. You might have a tough time for a few seconds if your eyes glaze over when the subject of mathematics comes up. I promise to be quick.

The mole is widely used in chemistry as a convenient way to express relative amounts of reactants and products of chemical reactions. For example, the chemical equation 2 H2 + O2 → 2 H2O implies that 2 mol of dihydrogen (H2) and 1 mol of dioxygen (O2) react to form 2 mol of water (H2O). The mole may also be used to express the number of atoms, ions, or other elementary entities in a given sample of any substance. The concentration of a solution is commonly expressed by its molarity, defined as the number of moles of the dissolved substance per liter of solution. This takes me back to my days of quantitative analysis in chemistry lab in grammar school. I used to be all right with the experiments, but I always managed to get tripped up on the mathematics at the end. I knew my chemistry backwards, forwards, and inside out – yet I still managed to make a simple error in calculation on the quantitative analysis in the final lab exam for ‘O’- level and fretted for a month until the results were published. Crisis over. Even with one simple error in multiplication on one tiny part of the whole exam I still got the highest mark. Phew !!

The mole is based on Avogadro’s constant, which is approximately 6.02 × 1023 (actually more like 6.02214085774×1023) and which is the number of particles (usually atoms or molecules) in one mole of substance. In the US writing style today’s date is 10/23, so at 6:02 (the time I woke this morning as it happens – late for me), we can say that we have approximated Avogadro’s constant (6:02 10/23) in the same way that 10/6 (October 6 in US, 10 June in Britain) is Mad Hatter’s Day, or 22/7  (22 July in Britain) is Pi Approximation Day. Semi-officially, Mole Day runs from 6:02 am to 6:02 pm.

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You can convert moles to grams by using the common isotope for carbon which is carbon-12. I mole of carbon-12 weighs 1 gram (which is also one way to define a gram – that is, 6.02 × 1023 atoms of carbon-12 = 1 gram). Carbon-12 is also the standard for all other atomic masses. Its nucleus contains 6 protons and 6 neutrons, giving a mass number of 12. Furthermore, carbon is the basic element of organic life because of its unique ability among all the elements to form long and complex chains or molecules. No other element even comes close in this ability. Without carbon there would be no life.

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According to current theory, the Big Bang did not produce significant amounts of carbon or other heavy elements (heavier than lithium). Mostly the Big Bang produced hydrogen and helium (constituent elements of stars, including our sun).  The heavier elements need extremely high temperatures to fuse the lighter nuclei of hydrogen and helium to make heavier nuclei, but the Big Bang had “cooled” below that temperature after only about 10 seconds. After the Big Bang, only very dense exploding stars were capable of generating such high temperatures and pouring out heavy elements. So all the carbon in your body was once part of an exploding star (as was all the oxygen, nitrogen, calcium, potassium iron, etc). Congratulations – You Are Stardust.

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If I go with molecules based on carbon-12 as today’s theme I have unlimited possibilities for recipes. Everything we eat, with the exception of salt, is organic (based on carbon). That’s not especially promising or limiting. But if we focus on Avogadro we can narrow things down. Avogadro’s full name was Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto, Count of Quaregna and Cerreto (9 August 1776 – 9 July 1856). He was born in Turin in the Piedmont region of northern Italy – then part of the kingdom of Sardinia. Avogadro graduated in ecclesiastical law at the late age of 31 and began to practice thereafter. But he soon became attracted to physics and mathematics and in 1809 started teaching them at a liceo (high school) in Vercelli, where his family lived and had some property.

In 1811, he published an article with the title Essai d’une manière de déterminer les masses relatives des molécules élémentaires des corps, et les proportions selon lesquelles elles entrent dans ces combinaisons (“Essay on Determining the Relative Masses of the Elementary Molecules of Bodies and the Proportions by Which They Enter These Combinations”), which contains Avogadro’s central hypothesis on atomic mass. In 1820, he became a professor of physics at the University of Turin. Avogadro was active in the revolutionary movement of March 1821. As a result, he lost his chair in 1823 (or, as the university officially declared, it was “very glad to allow this interesting scientist to take a rest from heavy teaching duties, in order to be able to give better attention to his researches”). Eventually, King Charles Albert granted a Constitution (Statuto Albertino) in 1848. Well before this, Avogadro had been recalled to the university in Turin in 1833, where he taught for another twenty years.

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Turin is most famous in Italy for its chocolate. Turin chocolate firms make all manner of chocolate products but are famous for Gianduiotto, named after Gianduja, a local Commedia dell’arte mask. The city is also known for bicerin, a traditional hot drink made of espresso, drinking chocolate and whole milk served layered in a small rounded glass. Every year Turin organizes CioccolaTÒ, a two-week chocolate festival run with the main Piedmontese chocolate producers, such as Caffarel, Streglio, Venchi and others.

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I’m not a big fan of chocolate, and even if I were to give you a recipe you’d need to come to Italy for the right ingredients (and atmosphere). The Piedmont region does have some savory dishes I like, however. One is paniscia, which in Italy is called “risotto” but is, in reality, a creamy version of the Hispanic staple, rice and beans. Paniscia originates in Novara, to the west of Turin, but is quite commonly found throughout Piedmont (and impossible to find elsewhere in Italy). You’ll have to make do with what you can find for meat/pork products. The whole Po Valley is famous for its regional sausages and hams. Use one or two semi-cured Italian pork sausages. Local ones in Piedmont are salam d’la duja, a somewhat soft, half-cured sausage finished submerged in pig fat, like a confit, and fidighina, with pig’s liver. Lardo is cured pork fat, for which you can substitute lard, and cotenna is cured pig skin, which you can replace with roast pork skin. Local cooks often use carnaroli rice rather than the more usual arborio rice used in risotto because it cooks up creamier.

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 Paniscia

Ingredients

¾ cup dried borlotti beans
½ head savoy cabbage, shredded
2 ribs celery, chopped
1 leek, cleaned well and chopped
4 oz Italian semi-cured sausage, diced
4 oz lardo or pork fat, diced
4 oz cooked pork skin, diced
¾ cup carnaroli (or arborio) rice
1 cup Italian red wine
1 tbspn butter (plus extra)
2 oz Parmigiano-Reggiano cheese
salt and pepper

Instructions

Cover the beans with cold water and soak them overnight.

Drain the beans and put them in a pot with the cabbage, celery, leek and salt to taste. Cover with water and bring to a simmer. Cook until the beans are tender but not completely cooked (around 2 hours). Keep the pot warm.

Place the meats in a wide, deep, heavy skillet and warm over medium-high heat. When the lardo starts to melt, add the rice. Stir with a wooden spoon to coat the rice with the fat. Continue to cook  for 2 to 3 minutes. Add the wine and allow it to reduce, stirring constantly.

Now you begin the risotto-making process which takes time and experience. Place on ladle of the bean broth in the skillet and stir. Controlling the heat is crucial. The broth should not bubble vigorously nor simmer listlessly. Somewhere in between. When the broth has nearly been absorbed add another ladleful. Keep stirring as the rice cooks and add more broth as it is absorbed. After about 15 minutes check the rice. It should be close to cooked. Start adding the beans and vegetables with the broth towards the last 5 minutes. The rice should be al dente and the whole mixture will have a creamy texture.

Remove the skillet from the heat, let it rest for 5 minutes, then add the butter and cheese. Stir thoroughly until the butter and cheese melt and are incorporated. Serve immediately

 

 

Feb 182016
 

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Today is the birthday (1745) of Alessandro Giuseppe Antonio Anastasio Volta an Italian physicist and chemist, who is credited as the inventor of the electrical battery and the discoverer of methane. Volta was born in Como, a town in present-day northern Italy (near the Swiss border). In 1794, Volta married an aristocratic woman, also from Como, Teresa Peregrini, with whom he raised three sons: Zanino, Flaminio, and Luigi. His own father Filippo Volta was of noble lineage. His mother Donna Maddalena came from the family of the Inzaghis.

In 1774, he became a professor of physics at the Royal School in Como. A year later, he improved and popularized the electrophorus, a device that produced static electricity. His promotion of it was so extensive that he is often credited with its invention, even though a machine operating on the same principle was described in 1762 by the Swedish experimenter Johan Wilcke. In 1777, he traveled through Switzerland. There he befriended H. B. de Saussure.

In the years between 1776 and 1778, Volta studied the chemistry of gases. He researched and discovered methane after reading a paper by Benjamin Franklin on “flammable air”. In November 1776, he found methane at Lake Maggiore, and by 1778 he managed to isolate the gas. He devised experiments such as the ignition of methane by an electric spark in a closed vessel.

Volta also studied what we now call electrical capacitance, developing separate means to study both electrical potential (V ) and charge (Q ), and discovering that for a given object, they are proportional. This is called Volta’s Law of Capacitance, and it was for this work that the unit of electrical potential has been named the volt.

In 1779 he became a professor of experimental physics at the University of Pavia, a chair that he occupied for almost 40 years.

Luigi Galvani, also an Italian physicist and Volta’s main rival, discovered a property he named “animal electricity” when two different metals were connected in series with a frog’s leg and to one another. Volta realized that the frog’s leg served as both a conductor of electricity (what we would now call an electrolyte) and as a detector of electricity, and that the frog’s animal nature was not relevant to the process. He replaced the frog’s leg with brine-soaked paper, and detected the flow of electricity by other means familiar to him from his previous studies.

<Fair warning> a few paragraphs of science follow for those who are interested.

In this way he discovered the electrochemical series, and the law that the electromotive force (emf) of a galvanic cell, consisting of a pair of metal electrodes separated by electrolyte, is the difference between their two electrode potentials (thus, two identical electrodes and a common electrolyte give zero net emf). This is sometimes called Volta’s Law of the electrochemical series.

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In 1800, as the result of a professional disagreement over the galvanic response advocated by Galvani, Volta invented the voltaic pile, an early electric battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and copper. Initially he experimented with individual cells in series, each cell being a wine goblet filled with brine into which the two dissimilar electrodes were dipped. The voltaic pile replaced the goblets with cardboard soaked in brine.

The battery made by Volta is credited as the first electrochemical cell. It consists of two electrodes: one made of zinc, the other of copper. The electrolyte is either sulfuric acid mixed with water or a form of saltwater brine. The electrolyte exists in the form 2H+ and SO42−. The zinc, which is higher in the electrochemical series than both copper and hydrogen, reacts with the negatively charged sulfate (SO42−). The positively charged hydrogen ions (protons) capture electrons from the copper, forming bubbles of hydrogen gas, H2. This makes the zinc rod the negative electrode and the copper rod the positive electrode.

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Thus, there are two terminals, and an electric current will flow if they are connected. The chemical reactions in this voltaic cell are as follows:

Zinc:

Zn → Zn2+ + 2e

Sulfuric acid:

2H+ + 2e → H2

The copper does not react, but rather it functions as an electrode for the electric current.

However, this cell also has some disadvantages. It is unsafe to handle, since sulfuric acid, even if diluted, can be hazardous. Also, the power of the cell diminishes over time because the hydrogen gas is not released. Instead, it accumulates on the surface of the zinc electrode and forms a barrier between the metal and the electrolyte solution.

<Fair warning ends>

With this invention Volta proved that electricity could be generated chemically and discounted the prevalent theory that electricity was generated solely by living beings. Volta’s invention sparked a great amount of scientific excitement and led others to conduct similar experiments which eventually led to the development of the field of electrochemistry.

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Volta drew the admiration of Napoleon Bonaparte for his invention, and was invited to the Institute of France to demonstrate his invention to the members of the Institute. Volta enjoyed a certain amount of closeness with the Emperor throughout his life who conferred numerous honours by him, including being made a count in 1810.

Volta retired in 1819 to his estate in Camnago, a frazione of Como, Italy, now named “Camnago Volta” in his honor. He died there on 5 March 1827, just after his 82nd birthday. Volta was buried in Camnago Volta.

Volta’s home town of Como is famous for its fish dishes made with fish from Lake Como. These include polenta e misultin (Alosa agone) featuring Como’s own style of polenta with shad, and risotto con filetti di pesce persico – persico is European perch (Perca fluviatilis). If you can read Italian you’ll find a good recipe here with numerous pictures as a guide http://ricette.giallozafferano.it/Risotto-al-pesce-persico.html . The dish is interesting because it features perch both in the rice and fried on top. As is common in some parts of northern Italy, the risotto may be creamy or drier – cook’s choice. This recipe uses carnaroli rice which is somewhat dry. Don’t be confused, as I was, when reading the recipe; il fumetto can mean cartoon or broth. Here you need broth !!! Make the broth with the bones and scraps from the fish you use for the dish. Be warned, making risotto properly takes years of practice.

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Risotto con Filetti di Pesce Persico

Ingredients

250 g perch fillet
320 g carnaroli rice
30 g carrots, finely diced
30 g celery, finely diced
30 g red onions, finely diced
1L fish stock
60 ml wine white
1 tsp sage
1 tsp rosemary
1 tsp thyme
45 g extra virgin olive oil
1 clove garlic, minced
15 g butter, cut in small chunks
salt and white pepper
grated zest of 1 lemon

Instructions

Have the broth simmering gently in a separate pan on the stove, keeping a ladle handy.

Cut half the fish in small chunks and keep the other half as whole fillets.

Heat the oil in a large, heavy skillet over medium heat, add the garlic for a few minutes, then remove it with a slotted spoon. Next add the carrots, celery and onion, sauté until wilted then add a ladle of broth. Let the broth evaporate, then add the herbs and rice. Toast the rice for a few minutes then add the wine and a little broth.

Here’s the part that takes practice. You must let the broth almost evaporate and then add another ladle until the rice cooks. The amount of heat is very tricky. It should not be so hot that the broth evaporates immediately, nor so low that the broth takes a long time to heat through. Keep evaporating and ladling broth until the rice is cooked but moist. During the cooking process you must keep stirring the rice.

Towards the end of the cooking process add the fish chunks, salt and pepper to taste, and lemon zest to the rice.

Meanwhile, if you have four hands, fry the whole fillets of fish to a light golden.

Remove the cooked rice from the heat and add the butter. Stir to melt. Serve the risotto on a warmed serving platter with the fried fillets on top.