Hey guys,

I decided to try and make Benedicts reagent for the lulz. My first step is obtaining Sodium Citrate but I have an issue I hope you can assist me with. I reacted citric acid and sodium bicarbonate to produce sodium citrate water and carbon dioxide. In a moment of stupidity I decided to add ethanol to the product to try and force the salt to precipitate rather than just evaporating off the water. I then attempted to evaporate off the water and ethanol and all was going well till about 80^oC when this happened:

 

 

My theory on this is it is a side reaction involving Fe contamination in the water. I tested the water I used and it was about .02 mg/L

 

Do you think it was an iron side reaction or what else could have happened. The result is a black smelly liquid which I am having a hard time evaporating off because every time I do it erupts like this. Is there a way to rescue my salt?

 

Cheers

Firstly, Benedict's reagent doesn't require non-aqueous chemicals. Reacting a known amount citric acid and sodium bicarbonate in stoichiometric quantities will give you sodium citrate in aqueous solution, which you can easily calculate the amount made.

 

Secondly, as I have made Benedict's reagent numerous times, I found that the quantities of chemicals used don't need to be precise. Simply adding excess carbonate solution to citric acid solution, then adding in a bit of copper sulfate made a blue solution that turned brown in the presence of glucose.

 

Finally, apart from iron contamination, the brown-yellow colour can also be partial decomposition of sodium citrate under heat, as organics are very prone to decomposing to a yellowish-brown liquid.

I am sure you may be able to buy Sodium Citrate,