Decant the supernatant liquid onto the filter paper using suction. Wash the remaining precipitate in the beaker 3 times with 0.12 M HNO3 and decant the washings onto the filter paper. Transfer the precipitate to the filter paper. Remove the precipitate from the beaker by using water from a wash bottle. Wash the precipitate on the filter with 0.12 M HNO3, 3 more times. Place the filter paper on a watch glass and dry it in the oven (110 C, ~ 15 min). Weigh the cool-to-room-temperature precipitate.