MICROCHEMICAL REACTIONS OF LEAD 
375 
is added to increase the delicacy of the reaction a double chloride 
of cesium and lead is formed which separates simultaneously 
with or even before the triple nitrite. 
EXPERIMENTS. 
a. Test a preparation containing Pb. 
h. Try another preparation, this time introducing RbCl. 
c. Try again with CsCl. 
d. By a series of careful dilutions determine the limit of the precipitation of 
Pb as the K salt, the Rb salt and the Cs salt. 
e. Test a mixture of Pb and Ni; Pb and Co; Pb and Ag. 
D. By Means of Metallic Zinc. 
Apply the fragment of metal to the center of the drop to 
be tested; see Method ///, page 300. 
The characteristic appearance of the different metals when 
separated from their solution by an element higher in the electro¬ 
chemical series is often quite sufficient to enable the analyst to 
identify it. The student is already familiar with these peculiari¬ 
ties through the experiments performed as outlined on page 254. 
Lead yields beautiful long stiff many branching more or less 
fern-like dendrites, whose side arms are usually at right angles 
to the main stem or rib. Only portions of the formation show 
bright metallic reflections. The chief characteristic of the “lead 
tree” is a long fairly straight trunk or rib with side dendrites of 
irregular length. 
Of “trees” formed by other metals that of silver most nearly 
resembles that of lead, but is more delicate, more branching, with 
side formations at angles other than 90 degrees and exhibits 
splendid silvery white metallic reflections. 
Tin somewhat resembles silver but the side arms of the “trees” 
are very oblique and parallel one with another, that is, the paral¬ 
lelism extends across the main axis or rib. The reduction is 
slower with tin. 
None of the remaining metals yield long loose fern-like or tree¬ 
like forms. Bismuth gives black and gray feathery and mossy 
dendrites with sharp-pointed ends with a characteristic curving 
tendency of the ends of the clusters. The mossy dendrites appear 
