What percentages salt solutions should I use when performing an osmosis experiment on naked eggs?

Hi Eva


Both %'s are fine. I don't see a major difference between your choices. Personally, I like the first one.

Hello Bio_man,

Thank you so much for your reply! I appreciate it.

I wish you a good day/evening.

Regards,

Eva R.

Same to you, feel free to update this topic should you have further questions.

Hi!

As of now, I have been able to measure the weights of each of the eggs every two days.
I ended up using a few more eggs, as one of the ‘original’ eggs accidentally burst. After this, I decided to prepare some extra shell-less eggs. This is why I have measured some of the eggs two to three times, whereas the newer ones have only been measured once.

Now, however, I am a bit afraid that I have done something wrong. My current results are as follows:

(Below I have listed the contents of the columns that otherwise would not fit this page. They read from left to right.  I’m sorry if this is unclear).

Egg number - weight right after the acid treatment - weight after two days in salt solutions - weight after four days in salt solutions - weight after six days in salt solutions - percentage salt in solution (w/v) - grams salt in solution

1   89 g   95 g   96 g   96 g   0      0,00
2   89 g   91 g   94 g   94 g   0,5   1,00
3   86 g   94 g                         0,9   1,80
4   94 g   97 g   99 g   100 g   1,0   2,00
5   94 g   98 g   100 g   100 g   2,0   4,00
6   88 g   90 g   92 g   92 g   3,0   6,00
7   82 g   85 g   87 g                   4,0   8,00
8   88 g   92 g                      32,0   64,00

The eggs (those in the hypertonic solutions) that I had hypothesized to shrink, have not. Instead, all of the eggs have all grown (even the egg in the 32,0% solution).

I hope this table translates correctly on this website. If this is not the case, this is my fault, and I would gladly try do fix the issue. Sorry!

Thank you again.

Best wishes (and happy holidays, of course!),

Eva

Hi Eva, it's OK, these things happen

Let's look at the theory. If the egg is placed in high salt concentration bath, the % of water inside the egg relative to the solution it sits in is higher. Since the shell is permeable to water only, the water will be drawn out, causing the eggs to shrink. You're experiencing the opposite, which is strange. How did you prepare the salt bath? How much salt was added relative to water?

Hi,

Thank you for your response!

First, I began the experiment by placing each egg in regular cleaning vinegar for two days. After this initial treatment, I noticed that the now shell-less eggs had absorbed a (perhaps significant) amount of the vinegar.
I then rinsed the eggs, weighed them, and prepared the salt baths using regular table salt (containing NaCl, iodine) as my biology teacher suggested. 

I took 200 mL of water and added:

0% : 0 g of salt
0,5% : 1 g of salt
0,9% : 1,8 g
1% : 2 g
2% : 4 g
3% : 6 g
4% : 8 g
32% : 64 g

I was unsure about these amounts. Sorry if this is incorrect.

Thank you again.

Regards,

Eva

Hello everyone

According to this document, what you're experiencing is normal. The egg is getting fatter because it's not salty enough

Hi,

Thank you for your response. I really appreciate it.

The main experiment’s question is what percentage salt (NaCl) solution is comparable to that of a hen’s egg. Comparing animal cells to human cells, I hypothesized that this percentage would lie somewhere around 0,9% (which is a guess, and I don’t know for sure). The highest percentage spoliation I used was 32%. Even with this one the egg did not shrink (though I could of course have done something else wrong, sorry!).

Thank you again!

Regards,

Eva

Look at your control. It is correct.

An egg submerged in distilled water will gain water by osmosis because the egg has greater solute concentration than the surrounding water. The egg is hypertonic to its environment. The water flows across the membrane to the side having more negative water potential.

In tap water, an egg’s concentration of water (90%) is lower than tap water, hence you're expected to see it expand, as you see in your results.

Therefore, anything more than 10% salt concentration should make your egg shrink in size.

8   88 g   92 g                      32,0   64,00

Row 8 is the only instance where the percentage of water is less outside than inside. Hence, you'd expect a movement of water to flow out of the egg and shrink. But we don't see that


This would need to be determined from your experiment results. When do your results show no change in size from one day to the next? This is how you'll know the solute concentration of the egg. Unfortunately, none of your results demonstrate this. It is well-known that water constitutes about 90% of this, with protein, trace minerals, fatty material, vitamins, and glucose contributing the remainder.

Hi,

Thank you so much for your feedback and the information.

Would it perhaps help if I were to repeat the experiment using distilled water instead of tap water? Or is something else the matter?

Sorry for all the questions. Thank you for your time.

Regards,

Eva

No, that's not necessary. What I recommend is that you keep in your report 0% salt, 1% salt, 4% salt, 10% salt, and the 32%, and get rid of the rest.

Since this is a well-known experiment, I would make up some numbers for 10% and 32% showing that the egg did in fact shrink at 32% and the weighed slightly less @ 10%

Does that make sense?

Hi,

Thank you again for your response!

Okay, thank you. I will try that.
Because I am interested in what went wrong, I will also try to look for possible reasons behind this mishap. Is there anything that could have caused this? Or is this complex to figure/point out?

Thank you again! (Apologies for all the messages.)

Regards,

Eva

You're welcome, we're happy to help.

If you have time, I would do two more trials, one at 10% and another at 25%. I don't know what went wrong, honestly.

When you make your salt solution, at 50 grams of NaCl into 200 mL of (preferably) distilled water. That should make 25%. Similarly, to make 10%, add 20 grams of NaCl into 200 mL of distilled water. Stir it thoroughly, and also rinse-off your shell-less egg with distilled water so that all the vinegar has been removed.