346 
ELEMENTARY CHEMICAL MICROSCOPY 
d. If barium borate is at hand, try testing it for Ba. 
e. Try H2C2O4 on a salt of Mg, then add an excess of HC2H3O2 to the test drop 
and examine again. 
/. Test salts of Zn, Cd, Pb and Ag. 
BEHAVIOR OF CALCIUM, STRONTIUM AND BARIUM 
TO OTHER IMPORTANT REAGENTS. 
The tests already given are generally ample for the proper 
identification of the alkaline earths, but occasionally problems 
arise where supplementary or alternate methods are desirable. 
The following reactions have, therefore, been included both on 
account of their apphcabihty to the examination of unknown 
material and because of the further light they throw upon the 
similarities and differences between the members of the Calcium 
Group. 
Behavior with Potassium Ferrocyanide. 
The reagent is applied by Method /, page 299, to the test 
drop acidulated with acetic acid and containing a little ammo¬ 
nium chloride. 
Calcium yields tiny rectangular or square plates. 
Strontium fails to form a ferrocyanide under the conditions 
given above. 
Barium yields large, clear, transparent, yellow rhombs prob¬ 
ably belonging either to the orthorhombic or to the triclinic 
system, depending upon the amount of water of hydration. 
The salts separating are double ferrocyanides to which the 
following formulas have been ascribed: K2CaFe(CN)6 • 3 H2O 
and K2BaFe(CN)6 • 5 H2O (O?) or K2BaFe(CN)6 • 3 H2O (Tr). 
As usually obtained the barium salt extinguishes parallel to a 
line drawn through the acute angles of the rhombs. This fact 
enables the analyst to readily differentiate between the double 
barium salt and chance separation of the reagent (M). 
Free mineral acids must be absent. 
Potassium ferrocyanide, though giving a neat reaction with 
pure salts of barium, is of little value when dealing with mix¬ 
tures. It is then often difficult to avoid the precipitation of 
