Tested Overhead Projection Series Compiled by
HUBERT N. ALYEA Princeton University
19. GROUP VI. THE SULFUR FAMILY
Dem. 563-PbS
+HD,
Toshow: Therestoration of paintings blacked by PbS. Materials: lead acetate-aq, 3% hydrogen peroxide, cell C-2, stirrer, NazS-aq, H2S04-dil. Procedure: To 50 ml water add 8 drops each of (CHaCOOj2Pb and NasS-aq; a slight black precipitate should form; if it does not, add more of the two reagents. Two-thirds fill each cell of C-2 with this (a) Stir. (b) Into one add one drop HaSOrdil. plus 5 ml of 3% HsOi Stir. Observatzons: (a) Black PbS forms, and settles to the bottom of one cell. (6) I n the other cell, the PbS dissolves to form white PbSOi (exhibit macro) which projects paler than (a).
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Procedure: Place Na2S03,NaCl, and XaHSOg respectively in the three cells of C-3; do not tell the class which each contains, let them guess at the conclusion of the experiment Make each plastic strip pink with KMn04-aq. Project the cell and contents, add some drops of HCl-dil. to each chamber, lower into them the plastic strips. Observations: The bisulfite and sulfite chambers, but not the NaCI, generate SO2which decolorizes the permanganate. Reaction equations are given in Dem. 564. Dem. 566-Liquefaction
of Sulfur Dioxide
Experzment developed by Isjrzn Noerdin and Crosby U . Rogers. To show:
The preparation and liquefaction of SOa
Materials: Special device SD-566. See Figure tone, dry ice, HCl-dil , NaHSOa.
Ace-
Reactions: (a) (CHaCOOjiPb NazS -* 2 CHZCOONa PbS 4 (black). (6) PbS 4 Hz02 + 4 H 2 0 PbS04 (white).
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+
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D. Sulfur Dioxide Dem. 564-Preparation
To show: 559).
of Sulfur Dioxide
Preparation of sulfur dioxide. (See Den%.
Materzals: NaHSO,, HCl-dil. cell G-1, Iatn04-dil., plastic strip about 6 X 2-in. Procedure: Project G-1 with 5 g solid NaHSOa in the generator chamber, HCI-dil in the dropper, and the receiving chamber empty. Coat the plastic strip with a pink layer of KMn04-aq, and lower it into the receiving chamber Drop the acid upon the solid. Obsewalzons: As SO2is evolved, it decolorizes the permanganate solution If KsCr&aq is used, green Cr+3forms.
SD-566.
Liquefaction Apparatus.
To show: Preparation of sulfur dioxide.
Construction of SD-566 A 4-02 wide mouth clear glass square bottle. Inside, stick with wax 2 flat-bottomed vials about 1 in. high and about V S and 314-in. in diameter. Insert a one-hole stopper earning a 13 X 100 ml test tube projecting inside the bottle, and file a slit along the side of the stopper to permit escape of excess SO%.
Materials: NaHS03, Na2SOa, HCl-dil., NaCl, cell C-3, three thin plastic strips about 6 X 2-in , KMnO.an.
Procedure: Project SD-566 with 1 ml water in vial B, with 5 g NaHSOa 5 ml HCl-dil in vial A, and with dry ice-acetone mush in tube C.
Dem. 565-SO,
from SO,= or HSOc
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Volume 45, Number 12, December, 1968 / A977
