Glucose Test using Benedict's solution

I encounter an experiment that requires to prepare different concentration of glucose solution for glucose test using Benedict's solution. In theory, a low glucose concentration will gives a green colour upon the glucose test, followed by yellow, orange and brick red colour when the glucose level increase.

I tried to prepare different concentration of glucose solution. It does not gives me green when the glucose level is low, the result it gives is like lesser brick red ppt in blue solution (as shown in the picture below).

The concentration of the glucose solution is (from left to right) 10%, 5%, 1%, 0.2%, 0% (control).

At first, I thought is my Benedict's solution is qualitative type, therefore it does not gives me a range of colour. However when I checked online and prepared my own quantitative Benedict's solution and tested it out, it does not give me a range of colour too, instead it gives a white ppt.

Below is the recipe I used to make my own Benedict's solution:

For quantitative Benedict's solution:

- Sodium Citrate (Dihydrate) - 17g

- Potassium Thiocyanate - 11g

- Sodium Carbonate (Anhydrous) - 10g

* Dissolved the above in 70ml of deionised water and warm it to let the solute fully dissolved, name this Solution A.

- Prepare 1.4g of Copper Sulfate (pentahydrate) and dissolved in 20ml of deionised water

* Add this copper sulfate solution to Solution A. Stir vigorously until a deep blue solution is formed. This will be your quantitative Benedict's Solution.

For qualitative Benedict's solution (normally I buy ready made Benedict's solution from Comak)

(I tried to make my own Benedict's solution just in case the ready-made solution I have has a different recipe which do not give me the result I want.)

Basically is the same as quantitative solution without potassium thiocyanate.

- Sodium Citrate (Dihydrate) - 17g

- Sodium Carbonate (Anhydrous) - 10g

* Dissolved the above in 70ml of deionised water and warm it to let the solute fully dissolved, name this Solution A.

- Prepare 1.4g of Copper Sulfate (pentahydrate) and dissolved in 20ml of deionised water

* Add this copper sulfate solution to Solution A. Stir vigorously until a deep blue solution is formed. This will be your quantitative Benedict's Solution.

Anyway the Benedict's solution I made gave me the same result like the ready-made Benedict's solution I buy from supplier. So I still can't solve my problem.

So I tried to change my solution. Instead of lab grade glucose, I bought Glucolin (blue container) and mix it in water to test for glucose. ;( Still give me the same result like the lab grade glucose. 

Then I tried maltose (similar to the one in the picture below, but mine is not this brand)

 

I use 5% maltose solution, which is 5g of this gluey stuff in 100ml of warm water.

I used this solution to test for glucose. It does gives me an orange ppt.

So in the end I tried using 5%, 1% & 0.5% maltose solution to give me orange, lighter orange (still not yellow based on theory) and green/light brown.

Then I used 10% lab grade glucose to get brick red ppt. Below is picture of the result I got. From left to right, 10% glucose, 5%, 1% & 0.5% maltose solution.

This is the best I can get. If you also encounter this problem, can try using maltose solution. Or if you have successfully done this experiment before, please share with me the glucose solution & the Benedict's solution you used.

Spherification

Isn't it amazing to see water droplets to form a sphere? Here it is. The reaction of sodium alginate and calcium chloride will do this magic.

These sphere can be eaten too. First, you can use any juice to mix with the sodium alginate powder. However the pH of the juice cannot be below pH 4, so syrup water should works well.

The concentration of the sodium alginate is 2% (i.e: 2g of sodium alginate powder in 100 ml of water/juice). It needs to be blend in a blender for about 1-2 min to mix it well.

Prepare 1% calcium chloride solution (calcium lactate will be better as it will not have a bitter taste).

Then use a dropper to drop the sodium alginate solution into the calcium chloride solution. Then you will see the sphere forming.

This is tried again using tap water but it does not work, which mean it needs the calcium ion in the water to help it form a layer to create a sphere.

Here is the picture of the sphere that  has been drained out. If you want to eat the sphere, please rinse with water before consuming it.

Here is the video! Happy watching!

Experiment to view stomata under microscope

Hi all, here is a new experiment I encountered for viewing stomata under a microscope.

You may wonder how to view a stomata under a microscope where the leaves is opaque and will block the light of the microscope. Then normal dissecting microscope can only view up to 80x magnification. Here is the method where you can view the stomata at 400x magnification.

All you need are light microscope, clear nail polish, clear scotch tape and a leaf.

Paint a thin layer of nail polish on the back of the leaf. Wait for about 5 min for it to dry. Then use a clear scotch tape to stick onto the leaf where the nail polish is. Then pull up the scotch tape to allow the nail polish imprint to stick onto the scotch tape. Then stick the scotch tape onto a glass slide and happy viewing your stomata imprint.

Here are the imprint I made.

Kundt's Tube

This video is taken from the demo lab of NUS High School. The student there made this Kundt's tube.

Kundt's tube is an experimental acoustical apparatus invented in 1866 by German physicist August Kundt.

That time, it was used to measure speed of sound in gas or solid rod.

Today, we used it to demonstrate standing waves and acoustical force.

To make this tube, we need a transparent horizontal pipe with styrofoam beads inside. Do note, do not use styrofoam beads that are too small as static will cause them to stick to the wall of the tube. I saw online that some put cork duct or talc in it, but I never tried before so not sure whether it works.

Then block one end and attached another end to a loud speaker that is attached to a signal generator to produce a sine wave.

Then you will see like what is appearing in this video.

DIY cloud chamber

Cloud chamber is a device that can be used to detect/show cosmic rays (particles from the universe). Cosmic rays are harmless and are invisible to us. Presence of cosmic ray will show a trace/track that run across inside the cloud chamber.

I get to learn how to make a cloud chamber from NUS High School of Math & Science. The video here show our DIY cloud chamber and the trace of cosmic ray. In the DIY cloud chamber, the trace cause by the ray look like shooting stars.

While in a real cloud chamber, the trace look like fire works. Partly because we purposely put an radioactive material in the middle to create the cosmic ray so we do not need to wait too long to see its trace. Here's the video of the real cloud chamber.

Here's the brief instruction on how to make your own cloud chamber. Making it is easy however you may need to buy absolute isopropyl alcohol (pure / >99%) which may not be available commercially. You need to get it from those chemical supplier.

*Do note this isopropyl alcohol is denatured type, so do not drink it if you have excess of it from the experiment.

Things you need:

1) A clear plastic container (we use those tea bag container (w lid) from Ikea, but we don't need the lid)

2) Wooden Tray / shallow styrofoam box that is bigger than the clear plastic container.

3) A big piece of felt / absorbing cloth (available from Daiso)

4) Aluminium plate with black epoxy coating slightly bigger than the clear container but still able to fit into the wooden / styrofoam box.
*Paint coating aluminium is not suitable as it will peel off when contact with dry ice for too long.

5) Strip of LED light (length = perimeter of the clear container)

Procedure:

1) Roll up the felt and stick around the bottom of the clear container. We drill hole onto the container so string can go through and tied the felt to the container. As the felt must be able to stick there and not dropped when wetted with isopropyl alcohol.

2) Cut a rectangular felt where the perimeter is the same as the clear container (to seal the gap between the container and the aluminium plate)

3) Put dry ice in the wooden / styrofoam box.

4) Put the black aluminium plate on top of it.

5) Wet the rectangular felt and the felt inside the container with isopropyl alcohol. Do not add too much till the alcohol is dripping.

6) Invert it and put on top of the black aluminium plate

7) Put the LED light around it.

The coldness from the dry ice will cause the vapour to condense to form small droplets. When the ray pass by, these droplets will form track which you have seen it in the video.

My own video production on lab safety

Hi all, it has been quite some time that I did not write my blog. Partly is I am too busy & also I have nothing interesting to share.

As I have to do lab safety briefing for students at the start of the year. Using power slides to show all the lab safety rules will bored the students in this era where everything is shown with pictures & videos.

So I have decided to make a video from the 30 lab safety rules together with my school Media Studies student. I am quite impress with the students that are in the video. They can act and even do filming themselves. All the shots were created by the students themselves. I only told them what I want to show, then they know which angle or position they need to stand or film in order to get a good shot.

So instead of keeping such a good educational video only to ourselves. I would like to share this information to everyone and educate them on the importance of lab safety.

Here the link to the video. Hope you will like it.

Eating liquid nitrogen biscuit

Have you tried eating a biscuit that has been dipped into the liquid nitrogen? What will happen? Don't worry it will not be very cold to cause frost bite in your mouth. As you are eating the biscuit not drinking liquid nitrogen. (Please do not drink liquid nitrogen as it will kill yourself!). The taste of it? No taste of the biscuit only feel cold and dry.

The moment you eat it, the heat from your body will cause the liquid nitrogen to become gas. Hence what will happen? You will look like an angry bull with smoke coming out from your mouth & nose. Here is the video, happy viewing!