MICROCHEMICAL REACTIONS OF CALCIUM GROUP 349 
EXPERIMENTS. 
a. Try reaction on salts of Ba, Sr and Ca, in acid, neutral and ammoniacal solu¬ 
tions, and both in concentrated and in dilute solutions. 
b. Try mixtures of Ca and Ba, Sr and Ba; use solutions acidified with HC2H3O2, 
decant the clear solution, and to it add NH4OH. 
c. Try the reagent upon Ba and Sr salts in HNO3 solution. Then try it upon 
Ag, Pb and mercurous salts in HNO3 solution. 
Behavior with Primary Sodium Carbonate. 
An almost saturated solution of the reagent is added to the 
dilute ammoniacal test drop by Method /, page 299. 
Calcium carbonate CaCOs separates in very small disks and 
rhombs (H or O). 
Strontium yields spherulites often of considerable size. 
Barium separates as minute spider-like aggregates and tiny 
spherulites, the latter often uniting to form spindles and dumb- 
bell-like masses. 
The addition of the reagent in solid form gives nearly as good 
results. 
Warming the preparation increases the rapidity of the reac¬ 
tion and leads to the formation of better crystals. 
Unless the test drop is quite dilute an amorphous precipitate 
results. 
Ammonium carbonate can be substituted for the sodium salt; 
the crystals then differ but little if any from those obtained as 
above, but normal sodium carbonate gives amorphous precipi¬ 
tates only and therefore should never be employed. 
When simple salts of the elements calcium, strontium and ba¬ 
rium are employed it is not at all difficult to distinguish between 
them by testing with primary sodium carbonate (or ammonium 
carbonate). But if two or more of these elements are present 
the method fails, characteristic crystals being the exception. 
In the presence of a great excess of the reagent a double 
carbonate of calcium and sodium separates, having the formula 
CaCOa • Na2C03 • 5 H2O, which crystallizes in stout monoclinic 
prisms somewhat resembling the short, thin prisms of calcium 
sulphate. Strontium and barium prevent the formation of the 
double salt. 
