SCH4C                                                Qualitative Analysis
Group 2 Analysis Separation Table
The Acidic Hydrogen Sulphide Group
To the Group 2 precipitate obtained from the Group Separation Table, if present, add 5 mL of dilute HNO3, warm and filter if necessary. (reaction #9)
Precipitate:
To confirm the presence of Hg2+, add 1 mL of sodium hypochloride, (NaOCl) and 1 mL of dilute HCl and warm to dissolve the precipitate.  Add 2 mL of stanous chloride, SnCl2.  A grey or white precipitate confirms Hg2+. (reaction #10)
Filtrate:
Make the filtrate basic with NH4OH.  Filter if necesary. (reaction #11)
Precipitate:
Possibly Bi2S3 or PbS

Add NaOH (reaction #12)
 
Precipitate:
Bi(OH)3
Add 5 mL of sodium stannite. (1 mL of stannous chloride and add NaOH until the precipitate that forms redissolves) (reaction #13a)

A black precipitate confirms Bi3+ (reaction #13b)

Filtrate: 
Pb2+ 
Add dilute acetic acid until the solution is acidic.  Add 2 mL of K2CrO4.

A yellow precipitate confirms the presence of Pb2+
(reaction #14)

Filtrate: 
Possibly Cu(NH3)42+ or Cd(NH3)42+

If the solution is blue then Cu2+ is present.  Do the following.  Add HCl until the solution is neutral.  Then add 10 drops more.  Add some solid NH4Cl.  Let the excess settle, decant and pass H2S into the solution. (reaction #15)
 
Precipitate:
CuS
A black precipitate confirms the presence of Cu2+
Filtrate:
CdCl42-
Add NH4OH to make the solution neutral.  Pass H2S gas for 10 seconds.  A yellow precipitate confirms the presence of Cd2+.  (reaction #16)

 


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Copyright 1997, 2002, 2003  Tom Stretton (stretton@ripnet.com) Updated August, 2002 ts.