Uploaded by Karl Racaza

Method to use in Desiccator

Method to use in Desiccator. To open the desiccator, grip the desiccator with your arm and
use your other arm to carefully slip off the lid and place its greasy side of the lid up so that it
would not adhere to any dirt. Apply lubricant around the flat surface of the lid and use gloves
to place partially-covered sample inside the crucible holder so that you would not leave any
moisture traces from the body of crucibles. Put the cover back on using the same technique
using your arm and allow it to sit for several hours.
Method to use in Furnace. Turn the muffle furnace on and allow it to calibrate before opening,
once it had done its calibration, place the covered crucible in the furnace and close the
furnace door tightly. Set the temperature at 700⁰C for two hours and place a caution tag to
indicate that the furnace is running. After the combustion, wait the temperature to drop
below 250⁰C. Once done, detach the caution tag, turn the power off and take out the crucible.
Use a metal tong to hold the crucible and put it in the desiccator
Method to use in Determination of Sulfur:
Material Preparation. Place the labeled crucible and its lid separately in a hot air oven at
105⁰C for twenty minutes to remove moisture and avoid acquiring false sample weight. After
heating the crucible, use a metal tong to take the crucible out from the oven and cool it in the
desiccator. After drying, place the crucible without cover on the pan of the calibrated
analytical balance and slide the door back. Let the empty crucible sit for a while until there
is a line indicator for its final weight and record it.
Sample Preparation. Transfer the 0.2011g sample into a 600mL beaker. Add 5mL of 6M HCl,
dilute it to about 500mL, and heat it atop the Bunsen burner. While waiting it to nearly boil,
measure the calculated volume of 0.1M BaCl2, which is 6.2719mL plus 20.00mL excess a total
of 26.2719mL in a graduated cylinder, transfer it into a separate beaker and heat it atop to a
separate Bunsen burner. When the sample solution nearly boils, pour the heated BaCl2
solution and vigorously mix it using a stirring rod. Digest the precipitate, at just below the
boiling point for 30 minutes on a small flame until a white precipitate settles down.
Filtration. Decant the hot supernatant and allow the precipitate to settle down. Using a fine
filter paper, gently fold it in a half twice, and then fold it into a quarter of a circle. Open the
filter paper and round its sides and place it above a funnel atop the 600mL Erlenmeyer flask.
When transferring the liquid, touch the beak of the beaker to the stirring rod to directly and
safely transfer the liquid into the funnel. Once done, wash the precipitate using distilled
water until its chloride free.
Charring. After filtration, oven dry the moist filter paper at 105⁰C for one hour or until the
filter paper is dried to make it combustible. Char the crucible containing the precipitate with
a low flame in a prepared set-up of tripod with Bunsen burner until the paper completely
burn and volatile matters expel. Then, ash the sample in a muffle furnace at 500⁰C until
constant mass is obtained. After the combustion, transfer the crucible in a desiccator to
alleviate false sample weight and moisture contamination. Once cooled, place the uncovered
crucible containing the ash sample in the analytical balance and record the crucible plus ash
sample weight. Operate the analytical balance using the same method you did from the start.
Now, we can calculate the %S.
Formula of the %Ash:
%Ash = 𝑤
𝑤𝑠𝑎𝑚𝑝𝑙𝑒 −𝑤𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒
𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒 𝑤𝑖𝑡ℎ 𝑑𝑟𝑖𝑒𝑑 𝑠𝑎𝑚𝑝𝑙𝑒
Formula of %Moisture
%Moisture =
𝑤𝑠𝑎𝑚𝑝𝑙𝑒 −(𝑤𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒 𝑤𝑖𝑡ℎ 𝑑𝑟𝑖𝑒𝑑 𝑠𝑎𝑚𝑝𝑙𝑒 − 𝑤𝑐𝑟𝑢𝑐𝑖𝑏𝑙𝑒)
𝑤 𝑠𝑎𝑚𝑝𝑙𝑒