Sciencemadness Discussion Board

37% formaldehyde

chemrox - 8-4-2007 at 21:16

from formic acid one can make Ca Formate and from that formaldehyde gas. My question is: is there an easy way to tell when you get to 37% aqueous solution eg specific gravity? If so do you add the MeOH (stabilizer) afterwords? I would think so but the main question was how to tell when you get there.

Sauron - 8-4-2007 at 21:29

See Org.Syn. for an explanation of the difficulties in assaying aqueous formaldehyde by density.

Although their objections mostly had to do with varying amounts of methanol so if you are adding methanol afterwards you might be alright.

But you are going way long way round the block wasting good formic acid.

You make formaldehyde by running methanol vapor over heated copper. Methanol is a whole lot easier than formic acid to get and a lot cheaper.

But, formalin (37% soln formaldehyde) is also easy to get and cheap so I fail to see why you are bothering .

Also you can buy paraformaldehyde (solid) and very often generate formaldehyde in situ from it. Trioxane is also used in same way.

Biginelli - 9-4-2007 at 07:52

one of the best and most precise ways to analyze % of formaldehyde solution is DNPH (dinitrophenylhydrazine). It forms quite a stable hydrazone with almost quantitative yield -> gravimetric analysis, etc.