Hi,

The meaning is:

37% water in methanol as stabilizer ( 37g for 100g H2O and methanol added to prevent polymerization )

Please look at here:

http://mubychem.com/formaldehydesolution.html

But, "USP" is "United States Pharmacopeia". It's a label of the quality of your compound

Mr. Tao,

I shall agree with Mrs/MMiss Taleb.