Synthetic Inorganic Chemistry

280 ELEMENTS OF GROUP IV

residue of unoxidized lead, as Pb(OH) 2 , as well as calcium hydrox-
ide and calcium carbonate from the bleaching powder. By
treating this precipitate with nitric acid everything except the lead
dioxide is dissolved or decomposed, and practically pure lead diox-
ide remains.
The packages of bleaching powder are labeled with the percent-
age of available chlorine. This is the percentage by weight of
chlorine which would be given off if the material were treated with
dilute H2SO4.

CaOCl 2 + H 2 SO 4 -» CaSO* + H 2 O + Cl 2

It is to be noted that bleaching powder may contain unavailable
chlorine (e.g., CaCU). Calculate the weight of bleaching powder
with the given content of available chlorine (assume 30 per cent
if the package is not marked) that would be required to oxidize
the lead acetate used for this preparation. The so-called high-
test hypochlorite, Ca(OCl) 2 , which has recently become avail-
able in the chemical market, may be used in place of bleaching
powder.

Materials: lead acetate, Pb(C 2 H 3 O 2 ) 2 -3H 2 O, 95 grams = 0.25

F.W.

sodium hydroxide, NaOH, 25 grams,

bleaching powder containing 30 per cent available

chlorine, 66 grams, or calcium hypochlorite,

40 grams.

6iVHNO 3 ,250cc.

Apparatus: 8-inch porcelain dish.

2-liter common bottle,

suction filter and trap bottle,

mortar and pestle,

iron ring and ring stand.

Bunsen burner.

Procedure: Dissolve the lead acetate in 200 cc. of cold water in

the 8-inch porcelain dish; add a solution of the sodium hydroxide

in 100 cc. of water, stirring well, and into the mixture, which should

not be warmer than 30°, stir a paste made by rubbing 66 grams of

bleaching powder or 40 grams of calcium hypochlorite in a mortar

with a little water. Warm the mixture slowly to the boiling