Submitted by: Paul K. Glasoe, Wittenberg University, Springfield, Ohio 45501 Checked bg: E. C. Kostansek, Hiram College, Hiram, Ohio 44234 PREPARATION
+
Source of HzS gas (iron sulfide hydrochloric acid in a test tube generator is adequate.); 6 N HNOa; Conc. HNOa (15 N); 0.1M BaCIzsolution.
dilute the HN03 with an equal volume of water and add some BaC12 solution. A white precipitate shows the presence of sulfate. REMARKS
DEMONSTRATION
Bubble H2S gas slowly through 6 N HNOa. The solution becomes cloudy due to formation of elemental S. with only a slight evidence of brown NOz (due to some reaction of NO with air). Bubble H,S gas through conc HNOa. The solution remains clear and a considerable formation of brown NOzoccurs. After some reaction, discontinue the passage of H2S,
A644
/
lournof o f Chemical Edvcotion
Although some +4 sulfur compounds are probably formed in both cases, the principal reactions can be represented as (6Nj 2N01(Cone) 8NOs-
-
+ 3H1S + 2H,O+ 2 N 0 + 3S +6HzO + HzS + 6H80f- 8N02 + S O P + 10H20
The appearance of the reaction products serves to show that one can tell something about the degree of oxidation and reduction by such observations.
