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Sodium bicarbonate, or sodium hydrogen carbonate, actually has the formula NaHCO3.
The carbonate ion has a valency of 2-, so is balanced by one hydrogen ion (+1) and one sodium ion (+1).
Elemental sodium is a reactive metal as described above.
However, it is common to see 'sodium' listed in food ingredients. This refers to the sodium existing as sodium compounds, mainly salt (sodium chloride), within the food product.
In short - sodium is the element and sodium bicarbonate is an ionic compound of sodium.
The carbonate ion has a valency of 2-, so is balanced by one hydrogen ion (+1) and one sodium ion (+1).
Elemental sodium is a reactive metal as described above.
However, it is common to see 'sodium' listed in food ingredients. This refers to the sodium existing as sodium compounds, mainly salt (sodium chloride), within the food product.
In short - sodium is the element and sodium bicarbonate is an ionic compound of sodium.
Now that brachiopod has mentioned the listing of sodium in food products, I trust you�ll allow me to mention the furtiveness of many food manufacturers and supermarkets when they declare this information on the packaging. Forgive the chemistry lesson, but it�s necessary and I�ll try to keep it simple.
Common salt is a compound referred to by chemists as sodium chloride. It has the chemical formula NaCl. This formula shows that the compound is made up of only two elements, namely sodium and chlorine.
Now the ingredients list on many food products that you buy nowadays lists only the sodium content of the food product per 100 grams. However sodium is not sodium chloride (salt). Furthermore, we can relate what x number of grams of salt would look like in a slice of bread etc, but what does x grams of sodium look like? What does 1.3 grams of sodium look like when it�s in the form of salt? Let�s see how we can calculate the true salt figure in a product when only the sodium content is declared.
All atoms of elements are composed of many different types of sub-atomic particles. Two types of particles in the nucleus of an atom are called protons and neutrons. When the total number of protons and neutrons in an atomic nucleus are added together, they provide us with a figure called the mass number. The mass number is useful for a number of reasons, not least because it gives us the relative mass of an atom.
We need the atomic mass numbers to calculate the percentage mass of an element in a compound. Here�s the formula:
% mass of an element in a compound = (atomic mass x number of atoms of that element) divided by the total atomic mass of that compound. The resulting figure is then multiplied by 100 to give us the percentage mass.
Common salt is a compound referred to by chemists as sodium chloride. It has the chemical formula NaCl. This formula shows that the compound is made up of only two elements, namely sodium and chlorine.
Now the ingredients list on many food products that you buy nowadays lists only the sodium content of the food product per 100 grams. However sodium is not sodium chloride (salt). Furthermore, we can relate what x number of grams of salt would look like in a slice of bread etc, but what does x grams of sodium look like? What does 1.3 grams of sodium look like when it�s in the form of salt? Let�s see how we can calculate the true salt figure in a product when only the sodium content is declared.
All atoms of elements are composed of many different types of sub-atomic particles. Two types of particles in the nucleus of an atom are called protons and neutrons. When the total number of protons and neutrons in an atomic nucleus are added together, they provide us with a figure called the mass number. The mass number is useful for a number of reasons, not least because it gives us the relative mass of an atom.
We need the atomic mass numbers to calculate the percentage mass of an element in a compound. Here�s the formula:
% mass of an element in a compound = (atomic mass x number of atoms of that element) divided by the total atomic mass of that compound. The resulting figure is then multiplied by 100 to give us the percentage mass.
So as far as sodium chloride is concerned, lets go back to the formula NaCl. The atomic mass number of sodium is 23. Because there�s only one sodium atom in the formula NaCl, the atomic mass number remains 23 (ie 23 multiplied by 1). The atomic mass of chlorine is 35.5 and again there�s only one chlorine atom, so the figure remains at 35.5. If we add, the 35.5 and the 23, this will give us the total atomic mass of the compound, sodium chloride, which is 58.5.
The percentage of sodium in sodium chloride is now easy to calculate. We need only to divide the atomic mass of sodium, ie 23, by the total atomic mass of the compound ie 58.5. Multiplied by 100 to give a percentage, the figure is 39.3%. You can calculate the chlorine in the same way or substract one from the other, when we can then see that every 100 grams of sodium chloride contains 39.3 grams of sodium and 60.7 grams of chlorine.
So what does this mean in practice? It shows that whatever sodium figure a food manufacturer or retailer declares on an ingredients label, this figure is only 39.3% of the salt figure. Let�s call the 39.3% figure, 40% for ease of calculation.. This means that all declared sodium figures should be multiplied by 2.5 (40 x 2.5 = 100)to give us a the true percentage of salt in a product. For example, if a product states it contains 2% sodium, it actually contains 5% salt.
The percentage of sodium in sodium chloride is now easy to calculate. We need only to divide the atomic mass of sodium, ie 23, by the total atomic mass of the compound ie 58.5. Multiplied by 100 to give a percentage, the figure is 39.3%. You can calculate the chlorine in the same way or substract one from the other, when we can then see that every 100 grams of sodium chloride contains 39.3 grams of sodium and 60.7 grams of chlorine.
So what does this mean in practice? It shows that whatever sodium figure a food manufacturer or retailer declares on an ingredients label, this figure is only 39.3% of the salt figure. Let�s call the 39.3% figure, 40% for ease of calculation.. This means that all declared sodium figures should be multiplied by 2.5 (40 x 2.5 = 100)to give us a the true percentage of salt in a product. For example, if a product states it contains 2% sodium, it actually contains 5% salt.
Many food manufacturers and retailers play fair with consumers and declare percentages of sodium and salt in their products. However, it�s surprising how many big companies hide this information by declaring the sodium content only. It�s not illegal to do so unfortunately. The problem for the consumer is that many diets and dieticians refer to salt reduction figures and people do mistake sodium chloride for sodium.
Sometimes manufactures include other sodium salts in their products. As examples, sodium inosinate is a popular flavour enhancer since the demise of MSG, and sodium citrate is added to carbonated drinks to add sharpness and �bite�. When there are other sodium compounds in a product, the total sodium value may therefore not all be derived from the salt content. Nevertheless, current scientific opinion recommends the reduction of salt and sodium in the diet, so at the end of the day, the form in which the sodium exists in food remains immaterial. It just makes calculating salt values in a product more difficult.
Sometimes manufactures include other sodium salts in their products. As examples, sodium inosinate is a popular flavour enhancer since the demise of MSG, and sodium citrate is added to carbonated drinks to add sharpness and �bite�. When there are other sodium compounds in a product, the total sodium value may therefore not all be derived from the salt content. Nevertheless, current scientific opinion recommends the reduction of salt and sodium in the diet, so at the end of the day, the form in which the sodium exists in food remains immaterial. It just makes calculating salt values in a product more difficult.
Interesting post, theprof - what a lovely clear explanation - the Food Standards Agency would probably boggle at it - after all, according to their rather clumsy parameters, breast milk is junk food (salt and fat content) and I hope you're going to give up your daily 100g of junkey old marmite!!!! They find it far simpler to assume that all foods are eaten in 100g servings but have they been able to distinguish between sodium and salt content???
Rest assured, the FSA know all about it but their quite happy to allow the situation to remain at the status quo. It's not all their fault - the goverment and the EC are behind much of the legislation that's allowed this confusion to occur.
On top of this, food manufacturers have a lot of clout with governments for various reasons and although the government makes token efforts to show they're being influenced by no one, it does occur. As you imply, the recent junk food laws are a farce.
The 100g baseline is a useful method when it comes to comparison but often, you simply don't know how many grams of that product you're eating. It's all very well dividing the weight of your morning croissant into 100g and working out the calories etc, but who weighs the spread or butter they put on it? Who sits down and adds these figures together?
I love marmite and nothing on earth will stop me eating it. I'm not quite up to 100g a day yet though!
I advise this government myself on a number of matters mostly unmentionable but it does include some issues connected with food. However, I don't advise on matters relating to food labelling which this sodium/sodium chloride matter comes under.
However, I can tell you that some of my colleagues who do advise over food labelling issues have pointed out the confusion over this part of food labelling for some time. It seems even MP's have been lobbied over the matter. Right now, it doesn't seems to be priority matter for the government.
Considerable public money has been spent over the years to educate the public regarding the dangers of excessive salt consumption. Yet, it continues to be acceptable to allow sodium chloride content to be hidden as the lesser sodium figure in food products. It's little wonder it's not working.
Ah well, time to jump off my soap-box for tonight.
On top of this, food manufacturers have a lot of clout with governments for various reasons and although the government makes token efforts to show they're being influenced by no one, it does occur. As you imply, the recent junk food laws are a farce.
The 100g baseline is a useful method when it comes to comparison but often, you simply don't know how many grams of that product you're eating. It's all very well dividing the weight of your morning croissant into 100g and working out the calories etc, but who weighs the spread or butter they put on it? Who sits down and adds these figures together?
I love marmite and nothing on earth will stop me eating it. I'm not quite up to 100g a day yet though!
I advise this government myself on a number of matters mostly unmentionable but it does include some issues connected with food. However, I don't advise on matters relating to food labelling which this sodium/sodium chloride matter comes under.
However, I can tell you that some of my colleagues who do advise over food labelling issues have pointed out the confusion over this part of food labelling for some time. It seems even MP's have been lobbied over the matter. Right now, it doesn't seems to be priority matter for the government.
Considerable public money has been spent over the years to educate the public regarding the dangers of excessive salt consumption. Yet, it continues to be acceptable to allow sodium chloride content to be hidden as the lesser sodium figure in food products. It's little wonder it's not working.
Ah well, time to jump off my soap-box for tonight.
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