MICROCHEMTCAL REACTIONS OF CALCIUM GROUP 347 
calcium with the barium, particularly if much ammonium chlor¬ 
ide is present, or if much sodium acetate has been added to 
mitigate the action of mineral acids. 
From mixtures, strontium may sometimes be precipitated in 
an amorphous condition if the solution is quite concentrated, 
and may thus interfere with the test. Pure salts of strontium 
give, even in very concentrated solutions, only a granular deposit 
consisting of globular masses, exhibiting no distinguishable 
crystal form. 
Magnesium is precipitated from ammoniacal solutions, but 
neither from acid nor from neutral solutions; hence the pres¬ 
ence of this element will not mask the test for barium. 
In addition to calcium and strontium, there are a number of 
other elements, which, if present, will either be precipitated in 
insoluble form or will interfere with the formation of the barium 
crystals. In this list the most frequently met with will be lead, 
iron, zinc, rare earths and less often copper, mercury, uranium, 
and titanium. 
• EXPERIMENTS. 
a. Crystallize a little of the reagent K4Fe(CN)6, alone, and determine its optical 
properties. 
b. Try reagent on pure salts of Ca, Sr, Ba, using both dilute and concentrated 
solutions. Try again, this time proceeding as directed above, using HC2H3O2 and 
NH4CI. 
c. Try the reagent on mixtures of Ca and Sr, Ca and Ba, Sr and Ba. 
d. Try effect of the reagent on salts of Pb, Zn and Fe. Then make mixtures of 
Ba and these elements and test. 
e. Make a preparation of K2BaFe(CN)6, measure the angles of the crystals and 
determine the optical properties of the compound. 
Behavior with Ammonium or Potassium Bichromate. 
The reagent is applied to the test drop in solid form. Method 
III, page 300. 
From acetic acid solution, barium chromate BaCr04 is im¬ 
mediately precipitated, orthorhombic, in the form of minute 
light-yellow globular masses, or tiny rods with rounded ends. 
Strontium chromate will not separate from acid solutions but 
only from neutral or slightly alkaline solutions. Calcium is 
