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In this instructable, I will show you how to convert corn starch into glucose syrup. The following steps are involved:
  1. Hydrolyze corn starch with dilute sulfuric acid and heat as a catalyst.
  2. Create calcium carbonate using baking soda and dehumidifier.
  3. Neutralize hydrolized mixture using calcium carbonate.
Safety:
  1. ALWAYS wear eye protection. Sulfuric acid (especially when concentrated) can cause immediate blindness.
  2. HIGHLY RECOMMENDED to wear gloves. Acid burns take a long time to heal.
  3. HIGHLY RECOMMENDED to wear dust mask when making calcium carbonate.
  4. Do this at your own risk, I assume no responsibility.

Step 1: Hydrolysis of Corn Starch

Commercially, glucose is made by breaking down starches into sugars using an enzyme. Before this method was viable, acid hydrolysis was used. This process is not economically viable because it takes a long time. Although a flask would have been better to use for this process, I find that an enamel coated pot works just as well, with less risk of cracking.

Suitable sulfuric acid can be obtained in the form of battery acid, available at automobile stores. Acid taken directly from a battery SHOULD NOT be used since it is contaminated with lead. I used about 1 part battery acid for every 5 parts tap water.

The water and acid should be mixed together and then the solution brought to a boil in a suitable container. I used a strainer and a wooden stick to deposit the corn starch into solution. This reduces the size of corn starch clumps, leading to faster dissolution time. Add enough corn starch to to create clumps  in the water. Wait until it has completely dissolved before adding more.

This process can continue for some period of time so you may need to add more water. I used about 3/4 lbs. of corn starch and took about 3-4 hours to do so. In the meantime, consider doing steps #2 and #3.

Step 2: Sodium Carbonate

Ultimately, we'll want to use calcium carbonate to neutralize the sulfuric acid remaining in solution. To do so, we first need to create sodium carbonate by heating baking soda. In the process, baking soda releases water vapor and some carbon dioxide. In this step:
  1. Heat baking soda.
  2. Stir heated mixture.
  3. Stop when temperature at or above 100°C.
  4. Wait for mixture to cool.
Please wear a dust mask in this step. Sodium carbonate is extremely unpleasant to inhale and is basic, meaning that it acts slightly like lye (Sodium Hydroxide). Wear gloves/wash hands as necessary. Note that the final product is in the form of a monohydrate, meaning that each unit of sodium carbonate exists with a unit of water.
  • Na2CO3•H2O

Step 3: Calcium Carbonate

In this step, I make calcium carbonate. Here are a few alternatives that I considered that did not work:
  1. Antacid Tablets - No way to get rid of the flavoring.
  2. Egg Shells - Proteins leave bad smell / flavor.
  3. Quick Lime - Sold in large (50 lbs.) batches.
  4. Sidewalk Chalk - Frequently made of gypsum instead of calcium carbonate.
  5. Limestone - Did not know of a local source.
With those options unavailable, high quality calcium carbonate can be created by reacting calcium chloride and sodium carbonate. The reaction is as follows:
  • CaCl2(aq) + Na2CO3(aq) → 2NaCl(aq) + CaCO3(s)
You may have wondered why Sodium Bicarbonate (Baking Soda) could not have been used. This is because the solubility of calcium bicarbonate is 16.6 g/100g of water at 20°C vs. 0.0013 g/100g of water at 25°C for calcium carbonate. It would be difficult to separate the bicarbonate from the salt (NaCl) solution. In the case of calcium carbonate it is much simpler.

Calcium chloride is typically found in dehumidifiers intended for use in closets. I found this particular unit at a local Dollar Tree store. I disassembled it by cutting the top flap off after opening.

To balance the equation above, I measured out 66 grams of Calcium Chloride Anhydrous (Meaning, Calcium Chloride without any water molecules) and dissolved it in 750 mL of water. Similarly, I measured out 75 grams of Sodium Carbonate Monohydrate and dissolved it in a different batch of 750 mL water. I finally mixed the two solutions together so that they would react and precipitate Calcium Carbonate.

I waited for the solution to settle and poured out the top salt water layer. I refilled with fresh tap water and waited for it to settle again. I repeated this process 4 times so that the water was no longer salty.
 
 

Step 4: Neutralize and Clump

In this step, neutralize any of the remaining sulfuric acid in the hydrolized solution using the calcium carbonate. Keep adding the calcium carbonate mixture, stirring with a plastic spoon until it no longer bubbles. The underlying equation is as follows:
  • H2SO4(aq) + CaCO3(s) → CaSO4(s) + H2CO3(aq)
  • H2CO3(aq) → H2O(l) + CO2(g)
Verbally, the reaction proceeds as follows. Gypsum and carbonic acid are formed when sulfuric acid and calcium carbonate react. Carbonic acid is unstable at room temperature and will decompose into water and carbon dioxide, causing bubbling.

Once you have neutralized the solution, heat it again. I'm not sure what mechanism is at play, but without heating, the solution is gelatinous and will not easily filter. Once reheated, the calcium carbonate clumps and the solution is more easily filtered so that the watery glucose can be separated from the gypsum / calcium carbonate mixture.

Step 5: Filter and Concentrate

In the last step, I used coffee filters and paper towels to filter the solution. This is an extremely slow and boring process. I recommend filtering 4-5 times to get as clear a solution.

Reheat the solution to remove any water so that the solution becomes a syrup. It will darken and will be cloudy due to any remaining calcium carbonate or gypsum remaining in solution. It will also be dark due to any burning from the previous/present heating steps.

Once in a syrup like consistency it can be poured into preheated glass containers for storage.

I'm not claiming that this is fit for human consumption, nor do I recommend that you should, but I did consume approximately 4 fl. oz. without any detectable health effects (other than insomnia due to excess energy).
Hi - cool instructable! - just have a question - Starch is a mixture of branched & linear chains - the amount of acid used determines sweetness and how much hydrolysis occurs. I guesstimated the two salts used to be .6m each and that you end up with .6 m of CaCo3 - what is the volume & ?m of H2So4...... Many thanks

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Bio: I'm an Engineer. I like hiking, flea markets, and electronics.
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