Röntgenkleinwinkeluntersuchungen an Lösungen eines Anthrachinonfarbstoffes

Abstract

In this paper a report is given about an attempt to determine the average particle mass of a vat dye in vat liquor.
During these investigations, preparative difficulties had to be overcome, since all decisive measurements had to be performed under exclusion of air-oxygen, i. e. in a nitrogen atmosphere. Due to the low mass of the particles studied – it lies by one to two orders of magnitude below that normally measurable by the X-ray small angle method – the particle scattering was very poor. The adaption of the small angle method to this extreme demands has been reported in former papers. The decisive point is a precision of measurement exceeding by far the usual one.
The dye was studied in vat form with concentrations of 0.53%, 1.00% and 1.48%. The scattering curves showed, in their innermost portion, significant interference effects, increasing with growing dye concentration. In their outer portion they coincide satisfactorily.
From the Guinier plot, a radius of gyration of 5.3 Å is obtained. The determination of the average particle mass from absolute intensity leads to a value of about 890. Since the molecular weight of the single particle is 750, the dye is present preponderantly in the monomolecular form, in the vat.