M. L. Crossley
1919 Journal of the American Chemical Society  
Hydroxy-anthraquinones, such as alizarine, anthrapurpurine and flavopurpurine, form copper, cadmium, nickel and iron salts when boiled in an organic solvent with the corresponding metallic chlorides, anhydrous sodium acetate, and nitrobenzene. These compounds appear to be normal salts in which the metal has replaced hydrogen of the hydroxyl groups. Similar hydroxy-anthraquinone salts of other metals have been prepared by this method but have not yet been thoroughly investigated. These salts are
more » ... ed. These salts are practically insoluble in cold water, but dissolve readily in methyl and ethyl alcohols as well as in acetone, from which solvents they crystallize fairly well. Wpol, when boiled in a water suspension of the copper, cadmium, cobalt, nickel, chromium and iron alizarates, is dyed a pale shade of the color which alizarine gives on wool previously mordanted with the corresponding metallic salt. The dye is evenly distributed through the fiber and appears to be as firmly held by it as in the case when produced in the mordanted fiber. This, it seems to me, is positive evidence that the color produced by alizarine or similar hydroxy-anthraquinones in mordanted fiber is a property of the corresponding normal salt of the metal whose salt was used to mordant the fiber and that it is evidence of a chemical reaction. This does not mean that the dyeing of the fiber is wholly a chemical phenomenon. Undoubtedly, physical phenomena such as surface tension, diffusion, adhesion, the colloidal state, etc., one or several, contribute to the distribution of the dye in the fiber and to its retention by it. On the one hand, Liechte and Suida, Liebermann, Guggiari2 have expressed the opinion that the alizarine lakes have the composition of normal salts, while, on the other hand, Biltz, Haller and others,a think that lake formation is a phenomenon of a colloidal character. It seems to me that the evidence will not justify the conclusion that the formation of an alizarine lake is wholly a physical or a chemical phenomenon, but rather should be interpreted to mean that it is the result of the combined action of physical and chemical phenomena. Long boiling and scrubbing of the wool dyed with the sparingly soluble alizarine salts mentioned did not result in removing any more dye than was removed by similar treatment of the wool previously mordanted and then dyed with
doi:10.1021/ja02233a025 fatcat:2wcpka3w6zdwfig34emkgudrti