S-itbmitl'ed by: Octavio Garcia and Fidel Villarreal, Institute Tecnologico de Monterrey, Monterrey, N. L., Mexico Checkedb y : F. B. Dutton, Michigan State University PREPARATION
Olibin four 1 X %in. test tubes, a 500 mi flask fitted with a separator\- funnel and deliveq tube, a Dewar flask or a similar container, a support, dry ice, isocone. XH40H, NaOH pellets, Na metal, FeaOa, and granular P W Yalcohol, ~ YII.CI ,, Preparea freezing mixture of dry ice and isopropyl alcohol in the Dewar flask. Assemble the apparatus as shown in the figure.
.@
DEMON!STRATION
rate ammonia gas in ( A ) and condense it in ( B ) . a small clean piece of sodium t o the liquid ammonia.. A blue solution jear. Concentrate the solution by adding more sodium, the solution will rhunge to a bronze color. Prep:ire a dilute (blue) solution of sodium in liquid ammonia in each of two test tubes. Add a small amount of iron(1II)oxide to one t o show t h a t i t catalyzes l,he rea¥tiois indicated by the loss of color 2Na+2NHZ-2Na++ZNH-,+Hz Add :1 few small crystals of NH4Clt o the second tube to show the reaction again indicate'd by rapid docolonzation.
2 NH&l
+ 2 Na
NHa ÑÑ
2 Na+
COW.
--
AQUEOUS
NU,
+ 2C1- + 2 NH, + H,
This demonstration shows that sodium is dissolved in liquid ammonia t o 'eld solutions which possess bronze color if concentrated and blue color if dilute. iscuss the . uro~erties of such solutions in terms of the following- equilibrium: . . Na (x i/)NH, f s Na(NH,)+, e-(NH,)-, aid the discomfort of ammonia vapors, maintain the solutions in the dry opropyl alcohol bath and remove thorn for observation occasionally or proidcquate ventilation.
+ +
+
J
MPLEXING AGENTS ubmitted by:
fieclceo by:
i
( Af f w hv A
d of Chemical E d u d o n
-
August 1962
>
W. G. Britton, Bemidji State College, Bemidji, Minnesota George Ferris, Michigan State Vniversity, East Lansing
PREPARATION Provide: four glass goblets or beakers, the first of contains several drops of phenolphthalein inator, the second several drops of p-nitrophenol soluor a pinch of the solid, a third a small crystal of Ill) chloride and five drops of I 2 M HCI, and a h with 1 ml 1 M potassium fluoride solut,ion or 1 m . 0.2 M Verscne solution or ot,her complexing agent to be discussed; a china pitcher containing 500 ml of water to which one drop of 14.8 A1 ammonia solution and 20 drops of 1 M potassium thioeyanat,e solution have been added. DEMONSTRATION 1. The lecturer falls each of the four glass goblets from the same china pitcher with "strawberry soda," ^lemonade," "wine," and 'Skater." 2 The contents of the first three goblets are then
poured hack into the pitcher and then refilled from the pitcher with "wine." 3. The contents of all four goblets are then poured back into the pitcher and each is then refilled from the pitcher with "water." In the first pouring, the ammonia solution turns the phenolphthalein pink and the p-nitrophenol yellow; the potassium thiocyanate forms a red-colored complex with the iron in t,he t,hird goblet and there is no reaction in the fourt,h. When the cont,ents of the first three goblets are poured int,o the pitcher, the acid in the third goblet makes the pitcher contcnts acidic causing the phenolphthalein and p-nit,rophenol t o hecome colorless. The pitcher contents are red due to the iron thiocyanat,e complex. When the contents of all goblets are poured back, the complexing agent in the fourth glass complexes the iron so that the resulting solution is colorless.
