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#1
04-04-2005, 08:45 PM
 SandWriter Guest Join Date: Oct 2000 Location: CA Posts: 511
Salt -> Increase Boiling Point, how much?

Hey All,

How much salt do I have to add to increase the boiling point of a quart of water how many degrees?
#2
04-04-2005, 08:55 PM
 Patty O'Furniture Guest Join Date: May 1999 Location: Bangkok/52/Male Posts: 8,869
Boiling and Freezing points of pure and salty water

I don't speak whatever language they are speaking on that page, but maybe one of our resident chemists will pop in and decypher it for us.
#3
04-04-2005, 09:25 PM
 ZebraShaSha Guest Join Date: Dec 2003 Location: Fuck, I'm in Greensboro Posts: 2,774
Can you define your question some more SandWriter? I would either need how many degrees you wanted it raised or how much salt you wanted to add. Without, there is no way to calculate.
#4
04-04-2005, 09:27 PM
 Nametag Charter Member Join Date: Apr 2002 Location: California Posts: 8,088
This chart says about 110?C.
#5
04-04-2005, 09:46 PM
 SandWriter Guest Join Date: Oct 2000 Location: CA Posts: 511
Quote:
 Originally Posted by ZebraShaSha Can you define your question some more SandWriter? I would either need how many degrees you wanted it raised or how much salt you wanted to add. Without, there is no way to calculate.
The instructions on the side of the Mac & Cheese box say to add a dash of salt to the water that the macaroni is boiled in. I'm curious as to how much a dash? 1/4 teaspoon? will raise the boiling point of the water.

Which just begs the question, if I add a bit more will it make the boiling point higher? And, does it really make a difference? Does adding 1 teaspoon make a difference at all? Or do I have to add in 3 tablespoons?

I'm starting with tap water....
#6
04-04-2005, 09:47 PM
 ZebraShaSha Guest Join Date: Dec 2003 Location: Fuck, I'm in Greensboro Posts: 2,774
Quote:
 Originally Posted by Patty O'Furniture Boiling and Freezing points of pure and salty water I don't speak whatever language they are speaking on that page, but maybe one of our resident chemists will pop in and decypher it for us.
All that page is really saying is that if you took 1 litre of water, a cube 4 inches on each side, and added 29.23 grams of salt, a cube roughly 1.14 inches on each side, the temperature would be raised approximately .5 degrees Celcius.
#7
04-04-2005, 10:11 PM
 ZebraShaSha Guest Join Date: Dec 2003 Location: Fuck, I'm in Greensboro Posts: 2,774
I'm getting roughly 9.232 x 10^-8 degrees Celcius.

By using Patty's cite, which says a .5 molar solution NaCl will produce a .5 rise in Celcius degrees, I assumed the rise would be fairly linear for our purposes. Using 1/4 tsp for a typical pot, which I assumed would be around 680 ft^3 (6 inches high, 1 foot across, cylindrical in shape), I got a solution about 9.232E-8 molar. Seems minimal.

Nametag - That is a saturated solution of NaCl. Huge difference.

(All the above calculations taken at 1 atm.)
#8
04-04-2005, 10:20 PM
 Catalyst Guest Join Date: Aug 2000 Location: Columbia/Charleston, SC Posts: 884
If I recall correctly, you add salt when boiling pasta to keep the pasta from sticking, not to raise the boiling temperature.
#9
04-04-2005, 10:45 PM
 daffyduck Guest Join Date: Aug 2003 Posts: 857
Quote:
 Originally Posted by ZebraShaSha I'm getting roughly 9.232 x 10^-8 degrees Celcius. By using Patty's cite, which says a .5 molar solution NaCl will produce a .5 rise in Celcius degrees, I assumed the rise would be fairly linear for our purposes. Using 1/4 tsp for a typical pot, which I assumed would be around 680 ft^3 (6 inches high, 1 foot across, cylindrical in shape), I got a solution about 9.232E-8 molar. Seems minimal. Nametag - That is a saturated solution of NaCl. Huge difference. (All the above calculations taken at 1 atm.)
You have a pot that holds 680 cubic feet of water? You must have a hell of a stove.
#10
04-04-2005, 11:34 PM
 HMS Irruncible Guest Join Date: Nov 2004 Posts: 7,175
To raise the boiling point of 1 kilogram of water by 1 degree celsuis, you would add 15.7 grams of salt.

Converting from metric to imperial measures is left as an exercise for the reader.
#11
04-04-2005, 11:37 PM
 SandWriter Guest Join Date: Oct 2000 Location: CA Posts: 511
Quote:
 Originally Posted by NattoGuy To raise the boiling point of 1 kilogram of water by 1 degree celsuis, you would add 15.7 grams of salt. Converting from metric to imperial measures is left as an exercise for the reader.
Okay, so in summation, adding a dash of salt to boiling water raises the boiling point by exactly "below measurement error" amount.

Can I hijack my own thread?

How does salt keep pasta from sticking to itself?
#12
04-04-2005, 11:45 PM
 HMS Irruncible Guest Join Date: Nov 2004 Posts: 7,175
Quote:
 Originally Posted by SandWriter Okay, so in summation, adding a dash of salt to boiling water raises the boiling point by exactly "below measurement error" amount.
Well, that depends on your measurement method. But suffice it to say that the change in temperature is not gastronomically important.

Quote:
 Can I hijack my own thread? How does salt keep pasta from sticking to itself?
Boiling pasta with salt is the best way to season it, but I am not aware that salt keeps pasta from sticking to itself. The best way to keep pasta from sticking to itself is to stir it for the first 2-3 minutes after adding it to the water. Try a practical experiment and let us know how you get on.
#13
04-04-2005, 11:52 PM
 Polycarp Member Join Date: Aug 1999 Location: A better place to be Posts: 26,718
In very loose terms, not attempting to be scientifically correct, the salt added to the tap water enables the gluten cooked out of the pasta to dissolve and remain dissolved, rather than sticking to the outside surface of the pasta and causing the strands/elbows/radiatore of pasta to stick together. One drop of olive or canola oil added to the cooking water also helps in this regard; apparently whatever gluten is, is partially non-polar.
#14
04-04-2005, 11:55 PM
 SandWriter Guest Join Date: Oct 2000 Location: CA Posts: 511
Quote:
 Originally Posted by NattoGuy Boiling pasta with salt is the best way to season it, but I am not aware that salt keeps pasta from sticking to itself.
Catalyst?

p.s. I always stir the pasta after I add it to the already boiling water so it doesn't stick together. Experiment done. To NattoGuy, you seem to want people to do all the work. You make us do the metric english conversion, you think up experiments for us to do, you believe everyone has an expensive, accurate, recently calibrated, 2 decimal place accurate, thermometer in their house....
#15
04-05-2005, 12:07 AM
 HMS Irruncible Guest Join Date: Nov 2004 Posts: 7,175
Quote:
 Originally Posted by Polycarp In very loose terms, not attempting to be scientifically correct, the salt added to the tap water enables the gluten cooked out of the pasta to dissolve and remain dissolved, rather than sticking to the outside surface of the pasta and causing the strands/elbows/radiatore of pasta to stick together. One drop of olive or canola oil added to the cooking water also helps in this regard; apparently whatever gluten is, is partially non-polar.
It is true that oil will prevent pasta from sticking. Everything else in the above post is factually incorrect.

Anyway, you shouldn't use oil to correct the sticking problem. Oil coats the surface of the pasta and prevents it from absorbing flavor of your sauce or other ingredients. The way to keep pasta from sticking is use plenty of water and stir vigilantly for the first few minutes of boiling.
#16
04-05-2005, 12:15 AM
 HMS Irruncible Guest Join Date: Nov 2004 Posts: 7,175
Quote:
 Originally Posted by SandWriter To NattoGuy, you seem to want people to do all the work. You make us do the metric english conversion, you think up experiments for us to do...
Whose dinner is this anyway, mine or yours? I gave you the boiling point calculation you asked for. I answered your salt question. You could just say "thank you."
#17
04-05-2005, 12:27 AM
 SandWriter Guest Join Date: Oct 2000 Location: CA Posts: 511
Hey Nattoguy,

Thank You.
#18
04-05-2005, 12:52 AM
 Catalyst Guest Join Date: Aug 2000 Location: Columbia/Charleston, SC Posts: 884
Quote:
 Originally Posted by SandWriter Catalyst?
After a quick googling, it would appear that I badly misremembered an episode of Molto Mario. The top several hits for a search on "pasta salt sticking" all indicate that salt is strictly a matter of seasoning, though they disagree on how much salt to add. They seem to also indicate that a bit of oil has no discernable effect on sticking. My apologies for not checking my facts before posting.
#19
04-05-2005, 02:09 AM
 1010011010 Guest Join Date: Jun 1999 Posts: 2,076
Raoult's Law... is what you're looking for.

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