The Chemistry of Hat Manufacturing - Lectures Delivered Before the Hat Manufacturers' Association by Watson Smith
page 95 of 178 (53%)
page 95 of 178 (53%)
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with water, at that temperature (212° F.) the colour is decomposed and
injured, for some of the methyl chloride in the compound is driven off. In fact, by stronger heating we may drive off all the methyl chloride and get the original Methyl Violet back again. But we have coal-tar colours which are not basic, but rather of the nature of acid,--a better term would be _phenolic_, or of the nature of phenol or carbolic acid. Let us see what phenol or carbolic acid is. We saw that water may be formulated HOH, and that benzene is C_{6}H_{6}. Well, carbolic acid or phenol is a derivative of water, or a derivative of benzene, just as you like, and it is formulated C_{6}H_{5}OH. You can easily prove this by dropping carbolic acid or phenol down a red-hot tube filled with iron-borings. The oxygen is taken up by the iron to give oxide of iron, and benzene is obtained, thus: C_{6}H_{5}OH gives O and C_{6}H_{6}. But there is another hydrocarbon called naphthalene, C_{10}H_{8}, and this forms not one, but two phenols. As the name of the hydrocarbon is naphthalene, however, we call these compounds naphthols, and one is distinguished as alpha- the other as beta-naphthol, both of them having the formula C_{10}H_{7}OH. But now with respect to the colours. If we treat phenol with nitric acid under proper conditions, we get a yellow dye called picric acid, which is trinitro-phenol C_{6}H_{2}(NO_{2})_{3}OH; you see this is no aniline dye; it is not a basic colour, for it would saturate, _i.e._ destroy the basicity of bases. Again, by oxidising phenol with oxalic acid and vitriol, we get a colour dyeing silk orange, namely, Aurin, HO.C[C_{6}H_{4}(OH)]_{3}. This is also an acid or phenolic dye, as a glance at its formula will show you. Its compound atom bristles, so to say, with phenol-residues, as some of the aniline dyes do with aniline residue-groups. We come now to a peculiar but immensely important group of colours known |
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