376 
ELEMENTARY CHEMICAL MICROSCOPY 
jet black by transmitted light, grayish by reflection, their growth 
is rapid and vigorous, finally occupying the entire area of the 
drop, and is characteristic of bismuth. Antimony yields black 
mossy dendrites but rarely feathery or curving; they appear 
more granular in structure. 
Copper separates as black, compact stout mossy masses with 
somewhat tabular or angular ends. 
Cobalt resembles copper somewhat but forms dendrites less 
readily. Nickel can be made to yield a crystalline deposit only 
with great difficulty; only small mossy patches are usually 
obtainable. 
Gold yields very compact mossy or granular dendrites and 
irregular botryoidal black masses which soon exhibit the char¬ 
acteristic golden yellow reflections of the metal. 
Precautions. 
To obtain the best results, the solutions should be practically 
neutral or only very slightly acid, otherwise the rapid evolution 
of hydrogen will cause the disintegration of the deposited crystal 
masses. If free mineral acid is present add sodium acetate. 
. Use only cold solutions. 
Employ only a very minute fragment of zinc, otherwise the 
area of metal upon which deposition can take place is so great 
that really characteristic growths will not be obtained. 
In general a moderate concentration is essential to the forma¬ 
tion of satisfactory dendrites. 
EXPERIMENTS. 
If a number of elements have not already been tested under Method III, page 
300, try a fragment of Zn in drops of solutions of salts of Pb, Bi, Sb, Sn, Cu, Cd, 
Pt, Au and Hg. 
SILVER. 
Crystal Forms and Optical Properties of Common Salts of 
Silver. 
A. ISOTROPIC. — Chloride (I); bromide (I); iodide 
(I or H). 
