Help with examination work of eggs vs salts

[DavidHHH]

Hi!
I am working on an examination lab, where I investigate how different salts and acids affect the coagulation of egg-white. Listed are the chemicals being used:

• AgNO₃
• CuSO₄*5H₂O
• NaCl
• Mg(NO₃)₂
• HCl

(The discussion is relevant for the salts only, since that's how far I've gotten, but if you have input on the acid as well, feel free to disclose 🙂)

What I've done is prepare stock solutions for 1,0 M of each salt and then dilute them in a solution of 0,025 dm³ with the concentrations being: 

0,1 M   0,16 M   0,22 M   0,28 M   0,34 M

It's lead to some pretty cool results, where the copper and silver solutions have coagulated the egg-white, but the sodium and magnesium had no visual effect. 

What I'm wondering is:

• Why did sodium and magnsium have no effect?
• Will the entire egg-white coagulate, or is there part of it that doesn't contain protein that will coagulate?
• Why did copper and silver have an effect?
• Could the method of mixing the two substances affect the coagulation? (Currently just pouring the solution into the egg-white and stirring with a glass-rod).

Thanks in advance! :)

[exchemist]

1 hour ago, DavidHHH said:

Hi!
I am working on an examination lab, where I investigate how different salts and acids affect the coagulation of egg-white. Listed are the chemicals being used:

• AgNO₃
• CuSO₄*5H₂O
• NaCl
• Mg(NO₃)₂
• HCl

(The discussion is relevant for the salts only, since that's how far I've gotten, but if you have input on the acid as well, feel free to disclose 🙂)

What I've done is prepare stock solutions for 1,0 M of each salt and then dilute them in a solution of 0,025 dm³ with the concentrations being: 

0,1 M   0,16 M   0,22 M   0,28 M   0,34 M

It's lead to some pretty cool results, where the copper and silver solutions have coagulated the egg-white, but the sodium and magnesium had no visual effect. 

What I'm wondering is:

• Why did sodium and magnsium have no effect?
• Will the entire egg-white coagulate, or is there part of it that doesn't contain protein that will coagulate?
• Why did copper and silver have an effect?
• Could the method of mixing the two substances affect the coagulation? (Currently just pouring the solution into the egg-white and stirring with a glass-rod).

Thanks in advance!

I found this which may help to explain: https://en.wikipedia.org/wiki/Egg_white. esp. this passage:

"Copper bowls have been used in France since the 18th century to stabilize egg foams. The copper in the bowl assists in creating a tighter bond in reactive sulfur items such as egg whites. The bond created is so tight that the sulfurs are prevented from reacting with any other material.  A silver-plated bowl has the same result as the copper bowl, as will a pinch of powdered copper supplement from a health store used in a glass bowl. " 

I believe there are disulphide and thiol (-SH) groups in egg albumen which will react with Cu and Ag. The reason why Cu and Ag bond in this way while Group I and II metals don't will be to do with the nature of the bonding. Gp I and II metals will only form fully ionic bonds, whereas Cu and Ag can form bonds with more covalent character, possibly with some π-contribution in the case of a 3rd row element like S. I can't remember much about this, though, so maybe someone else can help.