Science Buddies: "Ask an Expert"

Hello,

Currently, I am designing an experiment similar to the project idea, "Why Aren't All Medicines Pills?" on science buddies.

Here is the link: https://www.sciencebuddies.org/science- ... ml#summary

I also want to test the gelatin in ph levels similar to the acids in our stomach as well, so I researched a bit on drug solubility and how to make a solution with a ph level of 1. Apparently, HCl acid (Muriatic acid) works best. However, I am unsure of the safety of the item and how to handle it. I was wondering if there are any alternatives to this acid to achieve a ph level of 1?

If I do use this acid, should I mix it with water or prepare it in some way?

Thankyou!

You are correct that hydrochloric acid, HCl or muriatic acid, is the correct choice as it is the acid in the stomach used to digest food. If your school has a chemistry lab, you could have your teacher ask someone there to give you a weak solution of HCl with a pH of 1.0.

pH is calculated by the following formula:

pH = - log [H+] where H+ is the hydrogen ion concentration in moles/L

So, if you want a pH of 1, you need to have a 0.1 M solution of HCl
The log of 10^-1 M is -1 so the pH = -(-1) = +1

If you haven't had logarithms in math yet or studied molarity in chemistry, this isn't going to make sense so ask your teacher to try to find someone in the chemistry lab to help you. A 0.1 M HCl solution should be handled with gloves and eye protection. Any spills can be neutralized with sodium bicarbonate (baking powder).

Household white vinegar is an acid but its pH is about 2.4 so would not substitute for HCl as stomach acid. There are no other household acids I know of that have a pH of 1.

Let us know if you need more help.

Sybee

Thanks for the advice! Unfortunately, I did not learn about logarithms or molarity in chemistry yet.

I came across some information for the ph solution in another "Ask an Expert" topic.
Here is the link: viewtopic.php?t=6242 (It is the third post)

It stated that 10% HCl (12 M HCl) can be used as long as it is diluted with distilled water. I was wondering if it is necessary to use distilled water or just regular tap water? Since I am still designing the procedure for this experiment, everything is subjectable to change. I am planning to talk with my science teacher and figure out the materials available at school right after school starts again. Anyways, I'll make sure to keep you updated on the project!

By the way, I want to keep the liquids at 37 degrees Celsius. Is it necessary to heat the liquid or just the temperature in my workspace?

Thanks!

Hi,

You are welcome! Glad to help.

The link you sent says the same as what I suggested--make a solution of 0.1 M HCl as a substitute for stomach acid at pH 1. Concentrated HCl (12.4 M) can burn your skin and the vapors are VERY irritating to your nasal passages and eyes. As Donna suggested, try to get someone at your school to make 0.1 M HCl for you. And, yes, always use distilled water to make lab solutions.

FYI--one 'mole' of any chemical is the formula weight in grams and a one molar (1 M) solution contains one mole per liter.
HCl has a formula weight of 36.46, so a 0.1 M solution contains 3.65 grams per liter (g/L). If you want to get the jump on learning chemistry try YouTube. There are many good lectures on basic chemistry. I was a chemistry as well as biology major and the two sciences are great together!

In regard to your question about incubation at 37C, what we usually do in the lab is use a water bath that has an electronic temperature control. You could make a water bath by using a large pot of water on a hot plate or your kitchen stove. Put a digital thermometer in it and adjust the heat until you are able to keep it at 37C.

Do you have test tubes to do the digestion in? You would want to use a clear container so you can watch the pill or capsule as it dissolves in the HCl. If your school has a lab they should have some test tubes you can borrow. Try to borrow a rack to hold them upright in the water also.

If you have more questions, we'll be here.

Good luck!

Sybee

Hi, I agree with the previous comments, but I would add that hydrochloric acid only has a pH of 1 when the concentration is 0.1M. Also, you need to wear latex or nitrile gloves when handling such a strong acid, and you must avoid breathing in the vapors. You should also ask an adult for help in case something goes wrong.