19 декабря, 2015 
Pokraskin A solution of 350 grams of lead nitrate in 1 liter hot water is treated carefully at 95°C. with about 120 grams of soda ash and the precipitated basic lead carbonate is washed thoroughly with water. The moist material is transferred to a 2-liter flask fitted with stirrer and reflux condenser (Fig. 6) and mixed to a homogeneous paste with 600 grams of 90 per cent alcohol. One mole (228 grams) of very finely pulverized thiocarbanilide is added rapidly, followed by the addition, at 25°, of
1.3 moles of sodium cyanide (about 60 grams of technical material).*
• The HCN content of the sodium cyanide must be determined!
With vigorous stirring, the temperature is raised to 77°C. during the course of 1 hour, and then a small test portion is removed and filtered. The colorless filtrate should not be blackened by the addition of a pinch of basic lead carbonate. If it is, heating is continued for an additional hour, and the test is repeated. If the test is still positive, additional lead carbonate and sodium cyanide are added, but this should not be necessary if the correct amounts of reagents were used originally.
When the reaction is completed, the mixture is heated to boiling and filtered hot, extracting the residue with two 500-cc. portions of alcohol. The hydrocyanocarbodiphenylimide is allowed to crystallize out. The first fraction is entirely pure and weighs about 160 grams. The mother liquor, after concentration, yields an additional fraction of about 40 grams of nearly pure product. The yield is about 98 per cent of the theoretical amount. The hydrocyanocarbodiphenylimide crystallizes in yellowish prisms melting at 137°. The mother liquors contain hydrocyanic acid and must be handled carefully.
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