Uracil and its homologues may be obtained in many cases from the hydrouracils by the action of bromine, and subsequent elimination of the elements of hydrobromic acid; or by the condensation of aceto-acetic ester and related substances with urea, thiourea, guanidine, &c. Uracil, C4H402N2, crystallizes in colourless needles, is soluble in hot water and melts with decomposition at 335° C. Hydrouracil, C4H602N2, is obtained by the action of bromine and caustic alkalis on succinamide (H.
Carbolic acid, and liquid preparations of carbolic acid and its homologues containing more than 3% of those substances, except preparations for use as sheep-wash or for any other purpose in connexion with agriculture or horticulture, contained in a closed vessel distinctly labelled with the word " poisonous," the name and address of the seller, and a notice of the special purposes for which the preparations are intended.
In order to obtain the phenol from this distillate, it is treated with caustic soda, which dissolves the phenol and its homologues tegether with a certain quantity of naphthalene and other hydrocarbons.
Two primary divisions of carbocyclic compounds may be conveniently made: (I) those in which the carbon atoms are completely saturated - these are known by the generic term polymethylenes, their general formula being (CH 2), t: it will be noticed that they are isomeric with ethylene and its homologues; they differ, however, from this series in not containing a double linkage, but have a ringed structure; and (2) those containing fewer hydrogen atoms than suffice to saturate the carbon valencies - these are known as the aromatic compounds proper, or as benzene compounds, from the predominant part which benzene plays in their constitution.
For example: nitric acid and sulphuric acid readily react with benzene and its homologues with the production of nitro derivatives and sulphonic acids, while in the aliphatic series these acids exert no substituting action (in the case of the olefines, the latter acid forms an addition product); another distinction is that the benzene complex is more stable towards oxidizing agents.
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