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In a test tube introduce 1 g of urea, 4 cm3 of formalin,
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0.5 cm of a 25% solution of ammonia. The mixture is
refluxed for several minutes and then, after cooling, it is
poured into two test tubes. One of them is added 1-2 drops
of saturated solution of oxalic acid and stirred. Both test
tubes are heated in a boiling water bath for several minutes,
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cooled and added to the contents of each of them in 1-2 cm
of water.
In which of the samples was hardening of the mass?
Compare the solubility of the resulting substances in water.

Preparation of Novolac resin
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To the test tube introduce 1.5 cm 40% formaldehyde
solution and 1 g phenol. The mixture is heated to obtain a
homogeneous solution, add several drops of hydrochloric
acid and heat for 5-10 minutes. to the turbidity and
stratification of the contents of the test tube. The upper
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water layer is drained, water is added to a test tube 1-2 cm
and heated for another 1-2 minutes. Then the water is
drained, and the resin is transferred to the glass, where after
a while it hardens.
Preparation of glyphthalic resin
Into a test tube add 3 g of powdered phthalic
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anhydride and add 2 cm of anhydrous glycerol. The
mixture is heated for 15 minutes, and then a portion of the
solution is poured onto the glass. The film gradually
freezes, forming a clear resin. The second part of the liquid
is heated for another 5-7 minutes, dissolved in a small (2-3
ml) volume of ethanol, and then cover with a solution of a
piece of plywood. After a while, the alkyd resin freezes,
forming a brilliant layer.

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