IL FURFURAL POLYMER Submtlted by: Gregers 0strup, The Technical University of Denmark, Copenhagen Checked by: Vance Hamilton, Michigan State-XSF Traveling Science Teacher.
tATION
Prep2&rea stork solution of "hqu~d phenol," i.e., phenol ,ronta~ningapprox~matcly10% water. Provide furfural (terhnical grade su~table), a 7-cm porcelain d i ~ hro , nwntratcd hydrochlorir arid and a spatula.
considerable heat M o w the mass to stand unt11 the following day, when it is rcad~lyrcmwed from the dish and should be wa5hed and dried. The full ktrength of the polymer is ohtamed 111about one week REMARKS
Pour 10 ml of "hquid phenol" and 10 ml of furfural into th e porrelaiu dish and mix thoroughly with a qpatula Add 5 nil concentrated hydrochlor~c acid very sl(nvly with rontmuou?z stirrmg. Caution, spattering Imay CJCCUr. Prov~defor removal of fumes. The ml xturc ~ I I ~ I Ialmost S black with the evolut~onof
The nashed polymcr cake may be passed among the students with instructions to break it .I freshly prepared cake, that 13, one wh~chis 24 hours old, is easily broken hut is much more difFicult to break whell it has been aged for a pcr~odof a week or more The charactcrist~codor of the mgredientq may be noticed. The material shonld bc handled carefully, sincc ~t may contain small drops of hydrorhloric acid In c a ~ i t ~ r s
CHROMATE-DICHROMATEEQUILIBRIUM
(A
DEMONISTRATION
@tm 1d
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.
ege, W'llkes-Barre, Pennsylvania. e-NSF',Traveling Science Teacher
PREPARATION
l'rov~dc four 25-X 200-mm test tubes and the llowing solut~ons: 2 M AgNOs, 0.5 ik' K2Cr207, 5 M K2Cr04,1 'If BaCh, I A f XaOH, and 3 M NOa.
change the color, then add NaOH to return the original yellow color. To the fourth tube containing K2Cr207 add BarL (formation of yellow prec~p~tate). REMARKS
This demonstrates the equihhr~um DEMONSTRATION
Fill two t,est tubes with K2Cr04and add HNOa to one test, tuhe dropwise. Compare colors and explain. dd &KOa to each t,est tube (formation of red precipi,). To a third t,uhc cont,aining K&rO< add HNO3 to
2Cr0,yellow
+ 2H
+
%
Cn0,orange
+ H2U
The formatmn of the yellow BaCr04 ~ndiratcsthe reverse reaction of K2CrKh w t h water to form snnie CrO4=.
