The effects of acids on the removal of impurity from 2N grade silica have been studied using five leaching acids: 0.2 M-oxalic
acid (pH 1.5 and 2.5), c-aqua regia, 2.5%—HCl/HF, and 1%—HNO3/HF. The presence of 39 impurities in the 2N grade silica and the reference material (RM, 5N grade silica) were investigated
by neutron activation analysis (NAA), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS)
methods. Major impurities of the 2N silica were Al, K, Fe, Na, Ti, Ca, Mg and P. The fractions of the eight major impurities
were 99.2% and 90.9% of total impurity in the 2N and RM silica, respectively. Among the leaching acids, almost all of the
major impurities were removed effectively by the 2.5% HCl/HF leaching acid. All the major impurities, except for phosphorous,
as well as 21 minor and trace impurities could be determined by the NAA.