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Group # - Surname 1, Surname 2, Surname 3, Surname 4
Experiment No. 2
Sublimation is a change of state from the solid phase of matter directly into
the gaseous state. Using it as a means of purification requires the knowledge of
the effective differences in the characteristics of the substances present in the
mixture from where the desired substance is to be separated. Pure salicylic acid
sublimes upon heating leaving behind the impurities that may have
contaminated it.
In this experiment, the inorganic compound, sodium sulfate serves to
facilitate the sublimation of salicylic acid and at the same time, preventing the
impurities from volatilizing.
After the experiment, the learner will acquire knowledge to:
1. Separate/purify a substance by means of sublimation.
1. Evaporating dish
2. Filter paper
3. Heating set-up
4. Wire gauze
5. Crucible tongs
6. Stirring rod
7. Spatula
8. Weighing balance
9. Funnel
10. Salicylic acid and sodium sulfate
1. Obtain a clean and dry evaporating dish and place 0.5 g of salicylic acid.
Add 0.1 g of Na2SO4 and mix thoroughly.
2. Cover the dish with filter paper and fold-in the sides tightly against the sides
of the dish so that it will not catch fire when the set-up is heated.
3. Make tiny holes at the center of the filter paper covering an area about
the size of a 25-centavo coin. Obtain a glass funnel and plug its stem with
cotton. Determine it weight and invert it on the perforated filter paper
covering the evaporating dish. Make sure that the holes are covered totally
by the funnel.
4. Heat the set-up with a very low flame to sublimate the salicylic acid until no
more fumes is noted. Note down your observations. Let the set-up cool.
5. Weigh the funnel together with the crystals taking care that no crystals are
6. Place the crystals in a dry, sealed test tube for future use.
A. Sublimation:
1. Weigh of Na2SO4
2. Weight of salicylic acid
3. Weight of funnel
4. Weight of funnel + sublimate
5. Weight of sublimate (4 - 3)
6. Percent recovery
% 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑦 =
𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑢𝑏𝑙𝑖𝑚𝑎𝑡𝑒
× 100%
𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑎𝑙𝑖𝑐𝑦𝑙𝑖𝑐 𝑎𝑐𝑖𝑑 + 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑁𝑎2 𝑆𝑂4
1. What is the function of Na2SO4 in the sublimation of salicylic acid?
2. What happens with the salicylic acid when heated?
3. What happens to the gas collected in the inverted funnel?
4. What cooling system is applied in the crystallization of sublimate?
5. What is the advantage of using a cold funnel over that of a warm one as a
catchment system in the sublimation process?
6. What is the purpose of plugging the stem of the funnel?