MICROCHEMICAL REACTIONS OF LEAD 
373 
Alkalies convert lead chloride into a basic chloride to which 
the formula PbCb • 3 PbO • 4 H2O is generally assigned. 
Thallous salts yield with hydrochloric acid star- and cross-like 
crystallites differing considerably from those given by lead. 
There is little danger of confusing these two elements, since re- 
crystallizing thallous chloride from hot water, in which it, like 
lead chloride, is soluble, yields well-formed cubes. 
In the presence of chlorides of antimony and bismuth complex 
chlorides of low solubility are sometimes formed, against which 
the analyst should be on his guard. 
Silver gives an amorphous precipitate and mercurous salts a 
fine granular one without resolvable structure. 
EXPERIMENTS. 
a. To a drop of a concentrated solution of Pb(N03)2 add a drop of dilute 
HCl in the manner described above. Make several other preparations varying 
the concentration of the test drops. 
b. Recrystallize a preparation of PbCL by heating to boiling with a large drop 
of water. 
c. Recrystallize a preparation of PbCh in the presence of NaCl, another in the 
presence of KCl; of NH4CI; of CsCl. 
d. Test a solution of Pb and Sb. Then one of Pb and Bi. Then one contain¬ 
ing all three elements. 
e. To a preparation of PbCL add a drop of NH4OH. 
C. Through the Formation of a Triple Nitrite of Lead, Cop¬ 
per and Potassium. 
To the moderately concentrated neutral test drop add a 
trace of acetic acid, then a fragment or two of sodium acetate 
and of copper acetate. Stir. Then add a fragment of potas¬ 
sium nitrite. 
There is formed the salt K2CuPb(N02)6 as tiny squares or 
rectangular plates, or tiny cubes and rectangular prisms which 
are brown by reflected light, jet black by transmitted light. The 
crystals appear to be isometric. 
In this salt the potassium may be replaced by rubidium, yield¬ 
ing a compound of lower solubility, or by cesium which will give 
a salt of less and finally by thallium, one of least solubility and 
therefore the test of highest delicacy. These salts are probably 
