Chapter 19 Laboratory: Qualitative Analysis 347CUTIOA nS:
CyANIdE GAS!
Depending on the reaction
conditions, mixing strong acids
with ferricyanide, ferrocyanide,
or thiocyanate salts may cause
deadly hydrogen cyanide gas to be
evolved. The amounts we use are
much too small and the solutions
too dilute to present any hazard,
but be very careful when handling
these salts in solid form around
strong acids.z
dISoALp S : dispose of all waste
materials by pouring them into
the hazardous waste 2-liter
soft drink bottle. when you
complete this lab session, make
up a saturated solution of sodium
carbonate (washing soda). Add
the sodium carbonate solution
to the soft drink bottle until no
further precipitation occurs.
decant off the supernatant liquid
and flush it down the drain with
plenty of water. The precipitate
contains small amounts of barium,
chromium, and lead. depending
on your local environmental
laws and regulations, you may
be permitted to dispose of this
precipitate with your ordinary
solid household waste, or you
may need to take it to your local
hazardous waste disposal facility.CationH 2 SO 4 (3 M) HCl naOH nH 3 K 3 [Fe(Cn) 6 ] K 4 [Fe(Cn) 6 ] KSCn
ExampleWhite ppt; not soluble in
excess ammoniaWhite ppt; not soluble
in excess HCl; soluble in
excess ammonia; re-ppt’d
by excess nitric acidBlack ppt; not soluble in
excess NaOH; soluble in
excess ammonia; re-ppt’d
by excess nitric acidBlack ppt; soluble in excess
ammonia; re-ppt’d by
excess nitric acidAl3+Ag+Ba2+Ca2+Co2+Cr3+Cu2+Fe2+Fe3+Mn2+ni3+Pb2+Sr2+zn2+