EXPERIMENTS 293the chloride, nitrate, and sulphate, can exist in solution indicates
that stannous hydroxide is basic; but that the salts hydrolyze
very easily, with precipitation of basic salt, SnCl 2 + H 2 O ;=±
SnOHCl I + HC1, indicates that the base is a weak one.- Reducing Action of Stannous Salts, (a) Add SnCl 2
solution drop by drop, to 2 cc. of HgCl 2 solution diluted with
10 cc. of water. Notice the white precipitate which turns
gray and then black with more of the reagent.
(6) To 2 cc. FeCl 3 solution diluted with 10 cc. of water
add SnCl 2 until the solution appears colorless. Then test
for ferric ions by adding KSCN to a part and note that there
is no red color. Test for ferrous ions by adding a freshly pre-
pared solution of K 3 Fe(CN) 6 , and note the deep blue pre-
cipitate.
Tin has a marked tendency to develop the valence 4 character-
istic of the group, and in consequence stannous compounds are
strong reducing agents.
SnCl 2 + 2HgCl 2 ^ SnCL, + 2HgCl j
SnCl 2 + 2HgCl -»• SnCLt + 2Hg |
SnCl 2 + 2FeCl 3 -»• SnCl 4 + 2FeCl 2- Lead Salts, (a) Dissolve a little pure crystallized lead
nitrate in water and test with litmus noting that it is not
affected. Dilute the solution and note that there is no
precipitate of basic salt.
(6) Moisten some litharge (PbO) with water and test with
litmus, noting that the litmus is turned blue. Boil the litharge
a few minutes with 10 cc. of water, filter, and add hydro-
gen sulphide solution to the nitrate, noting a little black
precipitate.
That lead monoxide is soluble enough to give a precipitate of
lead sulphide and that the solution is alkaline enough to color
litmus blue marks it as exceptionally basic for a heavy-metal
oxide. The absence of hydrolysis of the lead salts is a further
evidence of the distinctly basic character of Pb(OH) 2.
- Amphoteric Character of the Hydroxides of Tin and
Lead. Dilute 2 cc. of 1N SnCl 2 with 10 cc. of water. From
a 10-cc. graduate add QN NaOH, noting the amount required