抄録
A colorimetric method for determination of formic acid in the ambient air is presented. It is based on Grant's, that is, formic acid is reduced to formaldehyde with magnesium and hydrochloric acid, and the formaldehyde is determined by the chromotropic acid method.
Water is used as sampling medium. The collection efficiency of water for formic acid is ca. 100% when 750 μg/m3 of formic acid gas is passed through 50 ml of water in a train of two fritted bubblers for 10 min. The pre-sent method is not interfered by other carboxylic acid, formaldehyde, ozone, nitrate, and nitrite. Carbonate which interferes for partial formation of formaldehyde during reduction, is purged by adding acetate. Sampling volume of air should be relatively large to gain the sufficient amount of formic acid for analysis because the reduction rate is very low (apparent rate is 16.3%). Calibration curve is quasi-linear between 0 and 18μg/ml with 2.8% of relative standard devn.
The average concn of formic acid in downtown Kobe from 9: 00a. m. to 3: 00 p. m. on 5 days during July 1978, is 6.9μg/m3
