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and lime should not exceed 2/3 of the volume of the bulb.
The flask is combined with a reverse water cooler, the open
end of which is protected by a chloralkulbic tube. The flask
is heated on a water heater for a quiet boil and boiled for an
hour. Leave for two days. Replace the refrigerator straight
and connect it to the bulb with the help of a curved tube.
The receiver is the Wurtz flask, which is hermetically
connected to the refrigerator, and its discharge tube is
protected by a chloralkulbic tube. Distillation of ethanol is
not carried out until dry.
6. Starch, 1% solution. 1 g of starch is stirred in 5
3
cm of water, after defending, water is drained. Washed 2-3
times, add a new portion of water, mix with starch, and then
the suspension is poured into 100 cubic centimeters of
boiling water.
7. Kuprum (II) sulfate, anhydrous. Crystalline СuSO 4
∙ 5Н 2О is heated in a porcelain cup on a sandy heater,
stirring regularly. The temperature of the heater should not
exceed 220 ° С. A white powder of anhydrous cupron (II)
sulphate is formed, which is stored in a dry glass with a
tightly closed crust.
8. Cooprom-ammonium reagent (Schweizer's
reagent). 10 g of crystalline cuprum (II) sulphate are
3
dissolved in 200 cm of water and 100 ml of 2 N sodium
hydroxide solution is added. A precipitate of cuprom (II)
hydroxide is made, which is washed with water to remove
2-
ions of SO 4 , after which it is filtered out on the Buchner
Bay. The precipitate of copper (II) hydroxide is dissolved in
a 25% ammonia solution. The latter fills up gradually,
constantly stirring the contents of the bulb. At the bottom of
the bulb must remain a certain amount of precipitate cuprum
(II) hydroxide. The solution has some time to settle, after
which it is filtered through a glass filter or drained by
decantation. The reagent is stored in a tightly closed crust
glass.