Science Buddies: "Ask an Expert"

hi
for my project{https://www.sciencebuddies.org/science- ... #procedure } it says to add the sodium alginate solution to the calcium citrate solution but it wont become a ball so how can i measure the height or diameter

my question is will it or won't it become a ball
plllzzz
my projet is due in 3 days

The 'clot' is produced by the alginate reacting with the citrate so try adding more alginate. Maybe there's not enough alginate in your solution to create a solid blob.

Hope this helps. Let us know if it works.

Sybee

Thanx
I added just the right amount of everything
but it still won't coagulate
doesn't the sodium citrate break down the calcium in the sodium alginate.
When I added it to my controlled soltion it coagulated perfectly
did i add enough calcium chloride
did i add enough sodium citrate
did i add too much
i don't knoww
HELPPPP

Thanx
I added just the right amount of everything
but it still won't coagulate
doesn't the sodium citrate break down the calcium in the sodium alginate.
When I added it to my controlled soltion it coagulated perfectly
did i add enough calcium chloride
did i add enough sodium citrate
did i add too much
i don't knoww
HELPPPP

You are correct. The alginate needs calcium in order to clot and the citrate removes it thus preventing coagulation.

When you said 'control' I assume you mean without citrate, right? So, in that case you get clotting. But when you added sodium citrate you got no clotting. If you used the same ingredients listed in the Materials and the same procedure then it should have worked.

One thing I just thought of. Was your calcium chloride dry or moist when you weighed it? CaCl2 has the property of absorbing water from the air and its container must be kept tightly sealed or the powder will eventually form a solution. The instructions tell you to weigh 1.3 g of CaCl2 and if the powder contained moisture then it would add to the weight and it would be inaccurate--you would have less CaCl2 in the bowl. I don't know if this would be enough to make a difference but it is something to consider.

I checked the Make it Your Own section to see if there might be some help there and one of the things suggested was to try 0.5% sodium citrate. You could try that and hopefully you would see some clotting at the lower citrate concentration. There was also mention that pH affects alginate coagulation:

"Spherification"—the molecular gastronomy technique you used in this science project—can be affected by pH, or how acidic or basic the solutions are. Try changing the pH of your sodium alginate solution (by adding acids or bases to make it more acidic or basic) and see how it affects the formation of the balls. You can try this both with and without sodium citrate.

I hope this helps. Let me know what happened.

Sybee

thank you soo much
i think that u were right about the calcium chloride
ill try it out today and let u know

Hey, I'm glad to help. Let me know if you get some good blobs.

Sybee

OMGGGG

THANK YOUUUS OOO MUCCHHHH
U HAVE NO IDEA HOW MUCH YOU HELPED ME
IT WORKED
I CANT THANK YOU ENOUGH

Yaay! Glad to hear that my idea worked. Congratulations! If you ever need help again, I'll be here.

Sybee