Tested Overhead Projection Series Compiled by HUBERT N. ALYEA
Princeton University
17. NITROGEN CHEMISTRY
Obsewations: SHICl smoke (is white but looks brown by the project,ed light,) arises from one cap only: the liglider NH3 (mol. mt,. 17) diffuses faster am1 reaches the HCL (niol. mt. 36.5) sooner, so that the NH,CI smoke forms a t the cap containing the HCI.
A. Nitrogen B. Ammonia Dem. 5 13-Ammonia
Note: The familiar smoke-ring box experiment (See Fig. and Dem. 17-7, Tested Deiiaonstrations, ALYEADUTTON, J. CHEW. EDUC.) is more impressively performed macro. However, a micro-box can be projected. Better, a toy engine which puffs out smoke rings projects well.
Generator
Iikpevinaent developed by C a d J . Alancuso. A convenient R H 3 generator
T o show:
Mate~ials: NH4CNS, tank of ammonia gas, ice-salt bath, plastic bott,le with stopper; aquarium valve. Pvocedui,e: Half-fill the bottle with NH,CXS crystals. Place in ice-salt bath. Now run in NH, gas until the bottle is 2/3 full of material. Insert tightly the stopper bearing the aquarium valve. Obsewatiom: The crystals pick up 457, NHa by weight t o form a liquid addition compound. Store indefinitely as a source of ammonia. Refe~ence: AMFELT,C. H., and MCCROSKY, C. CHEM. EDUC.,16, 193 (1939). Dem. 514-Ammonio
R . , J.
Diffusion through a Rubber Balloon
T o shofo: Thc mpid diffusion of ammonia t,hrough rubber. Afaterials: Three rubber balloons, hydrogcu (tank gas or Zn IICI); nnimoriia gas (tank gas or RaOH KHnCI), thread, lend pe~lcil.
+
+
Procedu~e: Blow up three halloo~iscach to about 100 ml volume with air, NH3, arid Ha respectively; tie with thread t o a pencil as all anchor, and project 011horizontal &age for 5 min. Obsewations: The balloon of air is heavy; the other hnlloons rise and tug nt thc pencil. In a few minutes NH3 begins t o leak through the rubber and t,hat balloon slowly sinks and colli~pses. Note: Have students calculate the weights of gas in the three balloons, using the forn~ulasair 4/j?\T1); NHE, If2, the volume of each balloon 100 ml, and atomic weights 1, 14, arid 16 for H, N, and 0 , respectively.
+
Dem. 5 15-Ammonium
T o show:
Chloride Smoke
Dem. 5 16-Secret
Writing: HgNH,CI
+
+ Hg
T o s h o w Formation of HgXH2CI Hg, formed as a conlirmatory test for Hg(ous) in cation analysis. Alatevials: C-1, a G X 3-in. sheet of clear thin plastic, HgN03-aq, HCI-aq, conc. RHPOH.
+
P~ocerltc~e:Wsite a message (for example HgNHE1 Hg) on the plastic sheet using HgN03-aq as ink (a little detergeut can be added). Let dry. Now mash it with HCI-aq, and quickly lower it into C-1 one-quarter full of cone. NH40H,so the plastic is suspended in NH3 gas. Obse~uations: Black writing appears, HgNHsCI
+ Hg,
C. Fixation of Nitrogen Dem. 5 17-Air + Al-amalgam E x p e ~ i m e n tdeveloped by C a d J . dfancuso. T o show: Reaction of aluminum amalgam with O2and Nz of the air. Afate~ials: A1 sheet or foil 4 X 4 in.; H-3, conc. H2S04, lieSon-aq, funnel medicine dropper. Procerlu~e: Nacro. I'olish the Al sheet with fine sand and wash well. Row rub a few drops of Hg t,lioroughly into it. Wait 1 hr. Now wash with a few drops of mates, ruruiing the washings into a culture tube. I'roject culture tube in H-3. Apply nitrate ring test, Dem. 528. Obseruations: Oxide, nitrites, and nitrates of A1 are formcd. A positive ring-test for riitrates is obtained.
Rate of diffusion; formation of NH4C1.
Afaterials: NHaOH-colic., HC1-conc., two coke caps, 2 medicine droppers. Proceduve: I'roject t,wo coke caps about 2 in. apart on the vcrtical stage of the projector. Add a dropperful of conc. HCI t o one, a d of conc. l\'HnOHto the other. Have the class decide wl~iehcap cor~tainswhich reagent,.
Dem. 5 18-Arc
Process for NOi
Expei~inaenldeveloped by C a d J . Mancuso. T o shofu: The formation of S O 2froin an arc in air, the I3irkland-Eyde I'rocess. Volume 45, Number 7, July 1968 / A567
