the crucible and contents from the oven after the three hour
drying period, cool in a desiccator and weigh. Calculate the
percentage of red gum as follows:
A = weight of crucible and contents after the water
B = weight of the empty crucible.
W = weight of the original sample.
18.104.22.168.1.2 Potassium perchlorate. - Carefully rinse the
funnel of the filtrator in the above extraction with a stream of
warm distilled water (50 to 60 degrees C.) collecting the
washings in the volumetric flask. Cool the washings to room
temperature then dilute the volumetric flask with distilled
water to the mark and mix. With the aid of a 20 ml. pipette,
quantitatively transfer a 20 ml. aliquot of the filtrate to
a 50 ml. capacity platinum evaporating dish. Place the
platinum dish and contents on a hot plate and carefully evaporate
the contents to near dryness. Complete the evaporation to
dryness on a steam bath. Place the platinum dish in a cold
muffle furnace, heat to 600 degrees C. and maintain this
temperature for 1-1/2 hours. Remove the dish from the muffle
furnace, cool and quantitatively transfer the residue to a clean
400 ml. beaker, with the aid of a steam of hot distilled water.
Dilute the filtrate to about 200-250 ml. with distilled water.
Add 4 ml. of a 35 percent nitric acid solution and mix, with a
stirring rod, during the addition of 50 ml. of a 10 percent silver
nitrate solution. Heat the beaker and contents on a steam bath
until the supernatent solution is clear. Collect the precipitate
in a tared crucible and wash with four 15 ml. portions of a 1
percent nitric acid solution. Dry the crucible and contents In
an oven at approximately 135 degrees C. for 1-1/2 hours. Cool in
a desiccator and weigh. Calculate the percentage of potassium
perchlorate in the sample as follows:
B = gain In weight of the crucible.
W = weight of original sample.