A Conversation for Common Salt (Sodium Chloride)

Peer Review : A29595559 - Salt (Sodium Chloride)

Post 1

Galaxy Babe - eclectic editor

Entry: Salt (Sodium Chloride) - A29595559
Author: Galaxy Babe - U128652

This is an FM rescue originally submitted by Researcher U220394 but his original entry has disappeared, and I can't seem to add his U-number to the author creditssmiley - erm It was then picked up by Tango and the humongous PR thread is here: F124179?thread=276217&latest=1

I've incorporated many of the comments, I've also added some of my own bits, and run the chemistry bit by h5ringer.

GB
smiley - galaxy


A29595559 - Salt (Sodium Chloride)

Post 2

BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows

I remember being in convo with Tango about this (in fact, mine is the last Entry on that humungous convo thread), but I never had a reply.

Also, about that time, I was in convo ewith somebody else who was saying that there ought to be an Entry on Common Salt, but I can't recall who it was. Neither can I find the threadsmiley - doh


A29595559 - Salt (Sodium Chloride)

Post 3

Galaxy Babe - eclectic editor

Hi BigAl, yes, I read your comments. I'm happy to hear your thoughts on the revamped entry and do let me know if I've missed anythingsmiley - dohit is a collaborate Entry so I am happy to add contributing Researchers to the author list smiley - smiley


A29595559 - Salt (Sodium Chloride)

Post 4

BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows

Well, from a quick skim it looks finesmiley - ok
The main things which I had in my 'notes' which I didn't see mentioned are:

smiley - modMedically: Ant-depressant/feel-good factor (There is far too much 'food propaganfa about at the moment, focussing on the bad points of excess of something, without mentioning the oppositer side of the coin. e,g. witness the 'alcohol police pointing out the increased incidence of prostate cancer in people who dsrink wine, without mentioning the positive effect of moderate consumption of red wine on heart disease smiley - grr)

smiley - mod Your RDA (of 6g/day) differs from mine (4g/day) smiley - erm. However, as I say, experts consider that the body requires only half this amount. Many adults in developed World eat as much as 10g/day due to processed foods with high salt content. Many people now react to salt in same way that body reacts to hard drugs. Suggests that salt need/cravings may be linked to same brain pathways as drug addiction and abuse.<smiley - modI think the Entry should say more about salt mining in Britain e.g. I didn't notice mention of the Cheshire salt mines (It's like a city underground there smiley - smiley. Also, there are places around the coast (artificial lagoons ) where people (particularly Romans) let in the sea, allowed it to evaporate, then scraped out the salt.


A29595559 - Salt (Sodium Chloride)

Post 5

BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows

Oh, another thing I had in mind was the salt-eating elephants of Kenya

http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=44378465

'An adult elephant requires 100g of salt just to keep alive'

(i.e. this emphasises the NEED for dietary salt in mammals)


A29595559 - Salt (Sodium Chloride)

Post 6

Galaxy Babe - eclectic editor

Have you already written those up? If I can insert them cut & paste I'd be grateful, I'll add you of course. I'll write something on the elephants myself, I saw that programme. The RDA I took from a ready meal in my fridgesmiley - doh


A29595559 - Salt (Sodium Chloride)

Post 7

BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows

No, I haven't. I just had them in my notes at A48576522.

Can't recall where I got my RDA from, but it's s'thing that needs to be checked out, particularly as it appears to be a bit of a 'moveable feast'smiley - erm


A29595559 - Salt (Sodium Chloride)

Post 8

Galaxy Babe - eclectic editor

Updatedsmiley - biroexcept for "Cheshire salt mines" which I'll have to researchsmiley - run


A29595559 - Salt (Sodium Chloride)

Post 9

lil ~ Auntie Giggles with added login ~ returned


http://www.greenheyes.com/pages/saltmine01.htm


hope this helps smiley - winkeye


A29595559 - Salt (Sodium Chloride)

Post 10

Galaxy Babe - eclectic editor

Thanks lil, it'll be tomorrow nowsmiley - ok

smiley - run


A29595559 - Salt (Sodium Chloride)

Post 11

BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows

Some initial thoughts:

smiley - mod'The most commonly known form of salt is known as table salt, or sea salt.'

It might be a good idea to prefix this with s'thing like, 'The term salt' is used to describe the product of the reaction of an acid wiyh an alkali, i.e Acid + Alkali > salt + water'

smiley - mod '... but lots don't see the many uses and the great importance of this tiny molecule.'. As you've said elsewhere, sodium chloride forms a giant ionic lattice. (There's no such thing as a sodium chloride molecule)

smiley - mod'The chemical element chlorine is located in group VIIA — the halogens — in the periodic table, with a relative atomic mass of 35.45.' > 'The chemical element chlorine, with a relative atomic mass of 35.45. is located in group VIIA — the halogens'.

smiley - mod'Salt can be a corrosive element'. It's not an element, it's a compound.

History of Salt

smiley - mod'Salt was the first garnish or additive used with food. It is important in preservation of food ...' Mention that this method of preservation was particularly important before the days of refrigerators and freezers.


Where is salt found?

'Salt is found naturally all over the world. Salt can be found in oceans and sea water as well as in underground salt deposits. Salt can be found in great beds left behind when salt-water lakes and inland seas have completely evaporated, the Dead Sea is a present-day example of this process in action.'

smiley - modMention that normal sea-water has an average concentration of 3%, but in the Dead Sea, up to 7.2% (i.e. more than twice the amount. Enables people to float in the Dead Sea reading smiley - thepostsmiley - laugh)

smiley - modRock salt deposits are usually mined, or occasionally (e.g. i Cheshire) water is pumped down and 'brine' (containing about 25% NaCl) is brought to the surface. Evaporated by vacuum evaporators.

smiley - modAlong the east coast of Britain from about 600BC was a string of small salt works. From the evidence left behind, it is apparent that these early salters evaporated sea water in shallow pottery dishers set on brick stands over fires. One firm in Essex continues to extract salt from sea water. Essex has a long coastline with numerous shallow inlets from which water evaporates, leaving behind water with a high salinity

In warm climates, salt is obtained by evaporation of shallow sea water by the sun to give 'bay salt'. (When Romans first occupied they imported salt from France (Gaul) where it was possible to prepare salt thus). After the Roimans left, the British salt industry thrived again.

smiley - mod By mediaeval times, salt was big business. The Guild of Salters controlled the import of foreign salt into Britain - mainly from Bay of Biscay. There were strict rules governing its handling. Could only be measured out by officials known as 'salt meters', and carried by 'salt porters'.


smiley - mod '..., and excreted by the body as a major component of urea. Salt is not a component of urea. Urea is a compound in its own right. I think you mean that salt is a major componbewnt of sweat and urine.

Ingesting Salt

'First and foremost it must be understood that humans as well as animals cannot live without salt, more specifically, without the sodium in salt.'

smiley - mod Worth saying here that the average adult human conntains about 300g of dissolved sodium chloride. As some of this is excreted each day in sweat and urine etc etc, it MUST be replaced if we are to function normally.

smiley - modIt's quite shocking to recall that once upon a time a trip to McDonald's...' Wonder if it's worth mentioning here the twisty blue salt sachet in potato crisps - which has made a comeback, so that people can make their own decision on whether or not to add it smiley - erm.

Other Uses of Salt

'Salts are used in highway safety: it is cheap and abundant and melts snow and ice readily.'
smiley - mod This is because it lowers the freezing point of water, i.e water has to be at a lower temperature than 0 deg C before it freezes.

'Some exasperated gardeners are tempted to use salt to kill pests such as slugs and snails...'.

smiley - modThis is because salt is 'hgroscopic' (absorbs moisture from the environment) so dehydrates the creatures.


Salt Wisdom

' if you spill salt you should gather some and throw it over your left shoulder in order to ward off the devil sat there'.

smiley - mod This is because the spilling of salt was considered to bring bad luck. This re-emphasises the high value that was placed on salt.

smiley - mod Also, in mediaeval times, important guests sat 'above the salt', and this saying is still alive today.


A29595559 - Salt (Sodium Chloride)

Post 12

BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows

This is an NHS website about salt being a 'natural antidepressant'.

http://www.nhs.uk/news/2009/03March/Pages/Saltanaturalantidepressant.aspx

smiley - biro It corroborates your figure of 6g/day being the RDA for NaCl - in the UK!!
(It also corroborates my figure of 4g/day, this being the RDA recommended by the United States Food and Drug Administration (FDA)).


A29595559 - Salt (Sodium Chloride)

Post 13

BigAl Patron Saint of Left Handers Keeper of the Glowing Pickle and Monobrows

... and this is an article on the Essex Salt Makers (at Malden).

http://www.maldonsalt.co.uk/History_of_Maldon_Salt.html


A29595559 - Salt (Sodium Chloride)

Post 14

McKay The Disorganised

This isn't scientific - but it's the best story of salt I know

Sodium Chloride

Just a little atom of chlorine, valence minus one
Swimming through the sea, diggin' the scene, just havin' fun
She's not worried about the shape or size of her outer shell--
it's fun to ionize
Just a little atom of chlorine with an unfilled shell.

Somewhere in that sea lurks handsome sodium
With enough eletrons on his outside shell plus another one
"Somewhere in this deep blue sea, there is a negative
for my extra energy
Yes somewhere in this foam, my positive will find a home

Then unsuspecting chlorine felt a magnetic pull
She looked down and her outside shell was full!
Sodium cried "What a gas, be my bride,
And I'll change your name from chlorine to chloride!"

Now the sea evaporates to make the clouds for rain and snow,
Leaving her chemical compounds in the absence of H2O
But the crystals that wash upon the shore are happy ones,
so if you never thought before,
Think of the love that you eat ... when you salt your meat!


A29595559 - Salt (Sodium Chloride)

Post 15

Trout Montague

Posts 22 and 23 of the original PR Thread still apply then.



A29595559 - Salt (Sodium Chloride)

Post 16

Galaxy Babe - eclectic editor

Apologies, I'll go through the old PR thread again to check what else I've missedsmiley - doh


A29595559 - Salt (Sodium Chloride)

Post 17

Galaxy Babe - eclectic editor

Previous PR thread:
post 10smiley - biro
post 11smiley - biro
post 16smiley - biro
post 26smiley - biro

Still to be done: post 25

Next red dotsmiley - run


A29595559 - Salt (Sodium Chloride)

Post 18

Galaxy Babe - eclectic editor

post 25: gonna need some help with this one, please, I don't know what to add/change/etc.

<>


You could also mention that in general a salt forms as a product of the acid/base neutralization reaction. In the case of NaCl:

HCl + NaOH --> NaCl + H2O

Periodic table, acid/base, osmosis and ions can all be linked to (in the periodic table entry you will also find the correct usage of the group numeration)

'disassociate' should be 'dissociate' (GB already fixed thatsmiley - biro)

You could also include some data such as the NaCl dissociacion constant or the solubility of NaCl in water. (I'll post them over here ASAP)

What do you mean by _relative_ mass?

It is not common to speak of NaCl as a molecule.

Interesting trivia: When you dissolve NaCl in water it uses up energy!!! Hence your soup gets some fractions of degrees colder when you put salt in!

The salt in the water makes it boil at higher temperatures and freeze at lower temperatures.

Impure NaCl is used to defrost streets.

Electrolysis of NaCl solutions give Hydrogen and Chlorine instead of Hydrogen and Oxygen.

The energy released by the formation of NaCl in a chemical reaction is often the motor for chemical reactions.

I could bring you the formation enthalpy and other relatively important thermodynamic data. (that's the sort of stuff you spend hours looking for, when you have to do some homework)


<,end post 25>>


A29595559 - Salt (Sodium Chloride)

Post 19

Galaxy Babe - eclectic editor

By the way, Trout, are you happy with the opening few sentences now? smiley - smiley

Previous PR thread:
Post 47smiley - biro
Post 51smiley - biro

I have to go nowsmiley - run


A29595559 - Salt (Sodium Chloride)

Post 20

h5ringer

smiley - biro< NaCl + H2O>>
Although correct, there is a danger of confusing the reader here. In general, the reaction between *any* acid and *any* base reagents results in what is known generically as 'a salt' plus water. However, this entry is about the compound Salt - sodium chloride - which is a specific instance of the acid+base reaction, in this case that between sodium hydoxide and hydrochloric acid. For example the reaction between calcium hydroxide - Ca(OH)2 - and sulphuric acid - H2SO4 - results in calcium sulphate - CaSO4 (the 'salt' from the reaction) and water - H2O.

smiley - birothe Alkaline earth metals > the Alkaline metals

smiley - biro <>
Remove this; it's just twaddle - saline is any *solution* of sodium chloride in water; Ringer's injection is a mixture of sodium, potassium and calcium chlorides that is used medically to replenish electrolytes

smiley - biro <>
You can add (after the bit about the density being 2.170 kg/l) that the solubility of NaCl in water is 35.9 g/100 mL at 25°C. As regards dissociation constant, this is a measure of the extent to which the NaCl compound dissociates into free Na+ and Cl- ions. You have already said <>

smiley - biro<>
To avoid working with miniscule numbers when talking about the weights of atoms, relative (atomic) mass is used instead. The relative mass of an atom of the isotope carbon-12 is taken as '12'. On this basis, naturally occuring chlorine, which comprises a mixture of two isotopes, Cl-35 and Cl-37, in the ratio 3:1 respectively, has a relative mass of 35.5. By the same criteria, sodium has a relative atomic mass of 22.99.

smiley - biro<> The dissociation of NaCl into sodium and chloride ions is endothermic - it requires energy input to achieve it; it therefore absorbs heat from its surroundings (the water) and cools it.

smiley - biro<> and <>
The latter is a consequence of the former. Any impurity in water will raise its boiling point and lower its freezing point, relative to that of 'pure' water. It's just that salt is readily available, dissolves easily and has a marked effect in raising/lowering boiling/freezing points. Hence putting salt on ice lowers the ice water's freezing point and so it melts.

smiley - biro<>
smiley - ermIf water is electrolysed, the only elements around are hydrogen and oxygen, whereas a solution of NaCl in water puts 4 elements into the pot: hydrogen, oxygen, sodium and chlorine. Chloride ions lose an electron and combine in pairs to form chlorine gas, while hydrogen ions gain an electron and combine, again in pairs, to form hydrogen gas, leaving sodium hydroxide dissolved in solution.


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