148 NON-METALLIC ELEMENTS IN BINARY COMPOUNDSsolid barium carbonate in small portions. Stir the mixture after
each addition. (If the carbonate is added too rapidly the mixture
will froth out of the dish.) After all the carbonate has been added
heat the mixture to boiling. Add an additional 5 grams of barium
carbonate and test the solution with litmus paper. If it is not
neutral add barium carbonate in small portions until the acid is com-
pletely neutralized and an excess of carbonate is present. Add 3
grams of barium peroxide, stir the mixture, and boil it gently for 5
minutes. Enough water should be added to make the total volume
600 cc.
Filter without suction into a 600-cc. beaker, keeping both the
funnel and the beaker covered with watch glasses to prevent the
solution from cooling and crystallizing prematurely. Add the
reserve 10 cc. of dilute HC1 to the filtrate and make sure that a
drop of the solution will turn litmus red. Pour the solution into
the crystallizing dish and allow it to stand uncovered until a
satisfactory crop of crystals is obtained. Barium chloride has a
tendency to "creep." To prevent this it is advisable to grease
the rim of the crystallizing dish. Decant the liquid from the
crystals, and wash them with a little distilled water. Dry them
thoroughly at room temperature on white paper towels.
QUESTIONS- How could you show that your preparation is a hydrate?
- Barium carbonate dissolves in water to the extent of 0.0023
gram in 100 cc. of water. Explain how it was possible to dissolve
the carbonate since it is so insoluble. Write an ionic equation. - Write equations to show how barium carbonate is prepared
from barium sulphate. Indicate the conditions for each step. - Dissolve a small amount of your preparation in 10 cc. of
water. Divide this solution into three portions. To one add a
drop of sulphuric acid; to the second add a drop of potassium
chromate; to the third add a drop of silver nitrate. Record your
observations and write ionic equations for each reaction. - To a solution of barium hydroxide add a few drops of hydro-
gen peroxide. Record your observations and write an equation.
What is the role of hydrogen peroxide in this reaction? - To a solution of BaCl2 add H 2 O 2 and explain why the same
effect is not observed as in Experiment 5.