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    No Lions And Witches---The Pantry Leads To Chemistry
    By Enrico Uva | February 4th 2013 07:30 PM | 7 comments | Print | E-mail | Track Comments
    About Enrico

    I majored in chemistry, worked briefly in the food industry and at Fisheries and Oceans. I then obtained a degree in education. Since then I have...

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    When I'm in the kitchen, it's hard to keep my mind off pure substances, even if I'm just getting items from the pantry. I picked up some MAGIC baking powder, looked at the label and wondered why sodium bicarbonate(baking soda) is the last ingredient, meaning there's less of it than anything else in the container. The pantry door once again became like the wardrobe in C.S. Lewis' novel, but instead of carrying me into a fantasy world of lions and witches, it brought me into the more interesting realm of chemistry.

    Unless there's an acidic ingredient like lemon in baked goods, there won't be anything to neutralize baking soda(NaHCO3) to produce the needed carbon dioxide. So MAGIC also has an acidulant, in this case monocalcium phosphate (Ca(H2PO4)2), which has more aliases than a rap star--the IUPAC name being the best: calcium dihydrogenphosphate.

    But why provide more acidulant than baking soda? The dihydrogen phosphate ion (H2PO4-) ion reacts with baking soda's hydrogen carbonate ion(HCO3-) in a one to one ratio.

    H2PO4-HCO3---> HPO42-+ H2O + CO2

    Dissociating to provide two moles of H2PO4- , a mole of Ca(H2PO4)2  reacts with a pair of baking soda moles. But doubling the latter's molar mass of 84 still amounts to less than the acidulant's molar mass of 234 grams per mole, so for every gram of baking soda, you need more Ca(H2PO4)2, 1.39 to be exact.  Finally, the primary ingredient is corn starch, which may also have the role of acting as a filler to accommodate teaspoon measurements but is definitely there to absorb moisture. Otherwise there would some reaction in the packaging stage or on the shelves, leading to a premature release of carbon dioxide.  
     
    Another surprise is the presence of calcium chloride(CaCl2) in most canned tomatoes. People from the Food Network believe the additive leads to lumpier sauces, and they advise cooks not to use tomatoes from cans. But one of the 3 brands in our pantry, Italpasta, is free of calcium chloride. What's more interesting is the strong industrial link between the ubiquitous calcium chloride and baking soda and soda ash(Na2CO3), a connection that is however vanishing, thanks to the less costly means of producing soda ash directly from the mineral trona

    (Na3CO3HCO3.2H2O).

    Exactly 150 years ago, in 1867,  using a method he had developed a few years earlier, the Belgian chemist Ernest Solway founded a company in order to produce sodium carbonate(soda ash).

    The compound is used mostly in glass-making to lower the melting point of silica, but it finds its way into many other consumer products. The method, which only consumes table salt and limestone, is brilliant in that it creates little waste. It reuses two intermediate products, carbon dioxide(CO2) and ammonia(NH3), and creates not only soda ash but our firming agent for tomatoes.

    The overall reaction, as is often the case in both natural and industrial processes, is very deceiving:

    2 NaCl(aq) + CaCO3(s) --> Na2CO3(s) + CaCl2(aq) .

    It's as if you would bring in the groceries, place them on the counter, walk away from the kitchen during the preparation of the meal, return just in time when the cooked meal is on the table and conclude:
                                                           groceries  --> lasagna. 

    You would not be acknowledging any of the cooking process. Calcium carbonate is sparingly soluble at neutral pH's. Adding a sodium chloride solution to it would yield insignificant amounts of products. But the Solway method begins by treating brine with NH3 gas to generate ammonium chloride(NH4Cl). In Solway towers, carbon dioxide is then injected to yield baking soda. Next heat is used to drive off carbon dioxide from the baking soda to yield soda ash and regenerating CO2, which is used again in the towers.

    The ammonium chloride meanwhile reacts with limewater(Ca(OH)2), releasing ammonia gas that is kept to re-initiate the cycle. The alkaline solution is produced by cooking calcium carbonate, which releases lime and which creates more carbon dioxide for the in-between reaction. Our calcium chloride is the byproduct of the step that releases ammonia.


    If an industry is only interested in making calcium chloride it can also rely on the direct action of 36% HCl (hydrochloric acid) on calcium carbonate. The reaction is 2 HCl + CaCO3 --> CaCl2 + H2O + CO2, and the recovered carbon dioxide is used to make soft drinks. A cheaper method that however produces a less pure product relies on the purification of natural brine water. First magnesium ions are precipitated out with the addition of limewater.

    The water is slowly evaporated which forces out sodium chloride solid, leaving behind the more soluble calcium chloride.


    The greater solubility of CaCl2 is part of the reason it is a valuable additive to street salt to melt ice in colder climates. Although CaCl2 is about three times as expensive as NaCl, its calcium ion does not harm plants like sodium ion does, and it melts ice at much lower temperatures than rock salt(NaCl)'s -10 oC limit. The reason why calcium chloride is a firming agent for tomatoes is one of the reasons it makes regular salt more effective at melting ice.

    It's because CaCl2 is hygroscopic--it easily attracts and holds on to water.

    Compared to table salt, calcium chloride tastes much saltier, but it cannot be used as a substitute. Ca2+ plays an important role in cell signalling, and cells are sensitive to high levels of the ion. Not surprisingly the lethal dose that will kill 50% of mice is only 1940 mg CaCl2 /kg of body weight as opposed to 4000 mg/kg for table salt. But the concentrations of calcium chloride in canned tomatoes is nowhere near toxic levels. It's not only approved in the United States but in Europe, which is usually fussier over fuzzier matters.

     















    Comments

    rholley
    Are we not talking of Ernest Solvay (1838-1922), Belgian chemist, industrialist and philanthropist; inventor of the Solvay process (which I seem to remember from my schooldays): not to be confused with the Solway Firth?


     
    The confusion between V and W in the Cockney accent features in Charles Dickens’ Pickwick Papers:
    Serjeant Buzfuz now rose with more importance than he had yet exhibited, if that were possible, and vociferated; ‘Call Samuel Weller.’

    It was quite unnecessary to call Samuel Weller; for Samuel Weller stepped briskly into the box the instant his name was pronounced; and placing his hat on the floor, and his arms on the rail, took a bird’s-eye view of the Bar, and a comprehensive survey of the Bench, with a remarkably cheerful and lively aspect. ‘What’s your name, sir?’ inquired the judge.

    ‘Sam Weller, my Lord,’ replied that gentleman.

    ‘Do you spell it with a “V” or a “W”?’ inquired the judge.

    ‘That depends upon the taste and fancy of the speller, my Lord,’ replied Sam; ‘I never had occasion to spell it more than once or twice in my life, but I spells it with a “V.” ‘

    Here a voice in the gallery exclaimed aloud, ‘Quite right too, Samivel, quite right. Put it down a “we,” my Lord, put it down a “we.”’
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    Hank
    Is there any real reason these things are sometimes X Firth and sometimes Firth of X?  Or just random Scots being batty? 
    rholley
    Don’t know the answer to that one.  But here’s a wee joke for you:
    A Scottish student is studying at an English University.  His mother comes to visit him:

    “How do you find the English students, Donald?”

    “Mother, they’re crazy.  My neighbour on this side keeps on banging on the wall, and the one on the other screams and screams into the night.”

    “How do you put up with them”

    “I just ignore them, and carry on quietly playing my bagpipes.”
    (Condensed from Celtic Jokes)




    Robert H. Olley / Quondam Physics Department / University of Reading / England
    UvaE
    Are we not talking of Ernest Solvay (1838-1922), Belgian chemist, industrialist and philanthropist
    That's the brilliant man indeed.



    not to be confused with theSolway Firth?


    The birthplace of Led Zeppelin bassist John Paul Jones is on that firth, apparently.


    Hank
    Really? I have made similar claims in jest, like that I was born in a boat off the coast of Ireland and smuggled to shore in the body of a horse, but I didn't know anyone else actually had been even 50% of that. What was his mother doing out there?
    the lethal dose that will kill 50% of mice is only 42.2 mg CaCl2 /kg of body weight
     Not according to http://www.inchem.org/documents/sids/sids/10043524.pdf which states:

    The acute oral toxicity is low: LD50 in mice is 1940-2045 mg/kg bw, 3798-4179 mg/kg bw in rats, and 500-1000 mg/kg bw in rabbits. The acute oral toxicity is attributed to the severe irritating property of the original substance or its high-concentration solutions to the gastrointestinal tract. In humans, however, acute oral toxicity is rare because large single doses induce nausea and vomiting.
    ...
    A limited oral repeated dose toxicity study shows no adverse effect of calcium chloride on rats fed on 1000-2000 mg/kg bw/day for 12 months.
     
    I'm surprised they use it to flavour tomatoes. I have just tasted a bit and I can confirm the reports that it has an unpleasant flavour. Very salty, yes, but also bitter, with a persistent metallic aftertaste.

    I'm sure it's not tox
     
     
     
    UvaE
    I'm surprised they use it to flavour tomatoes. 
    It's in there to make the the tomatoes firmer, not in there for flavor.

    Thanks for pointing out the error in the lethal dose. I made the correction and inserted a different reference confirming your figure.