# How to extract water from a solution in formamide

I'd like to determine the water content in a sample without buying an expensive machine (like Karl Fischer titrator). So I'd like to measure the water volumetrically. I've chosen formamide to dissolve the sample because of its high polarity.

I've dissolved a sample (approx. 20 g; composed of sucrose, glycerol and glucose syrup, water) in 50 ml formamide and like now to separate the water fraction again.

1) Let's assume there is 0,5 ml water dissolved in the formamide fraction, is it possible to add 30 ml solvent B and get so a fraction of 30,5 ml (30 ml + 0,5 ml)?

2) Instead of formamide, do you know another solvent A which dissolves the sample including the water (and the watercontent of approx. 20% in the glucose syrup)) and a solvent B which extracts the water phase from the solvent A?

• You can use Dean-Stark azeotropic removal of water with toluene or benzene – K_P Jan 20 '16 at 20:23
• Can't do you a brine wash? Prepare a saturated aqueous solution of salt, then do a liquid-liquid partition and collect the aqueous layer. The volumes of brine and water will not be additive, but the masses will be. It's not a perfect separation, but certainly among the easiest options. – Nicolau Saker Neto Jan 22 '16 at 21:48
• Maybe try silica gel? – G-man Jan 23 '16 at 7:29
• @K_P Thank you K_P for your useful advice! Is it possible to heat my solution of formamide up to 105°C without distilling also the glycerol? (I think glycerol (because it's an alcohol) will make an azeotrop with water and therefore I doubt if this method is suitable) – laminin Jan 23 '16 at 9:35
• I don't think you will have any problem with glycerol since it has a boiling point of $\ce{260 ^{\circ} C }$ Also I wouldn't use formamide at all. Just mix your sample with enough toluene with good stirring and let it reflux using the Dean-Stark and collect and measure the amount of water. Formamide usually contains some water so this can affect your calculations depending what accuracy you need – K_P Jan 23 '16 at 10:07