Thanks to very careful monitoring of the raw materials which we use and a large number of quality control procedures during the production process, through to the goods departure inspection before dispatch, we have been able to guarantee for many years that our Tonsil® bleaching earths are of excellent and consistent quality.
With the introduction of a certified quality assurance system at our main plant in Moosburg, based on DIN
ISO 9001/14001, in 1992, all measures have been directed towards quality assurance according to this standard, and implemented into a fully documented system. This has undoubtedly led to the raising of our quality level still further in the manufacture of Tonsil® bleaching earths, and to increasing the performance of our production facilities.
Laser instrument for particle size analysis Grinding and drying installation at our Moosburg facility
is carried out in a laser interferometer, in suspension or in an air jet. The instrument is controlled by a
small computer, which calculates the particle size distribution from the interference pattern of the laser.
The filtration properties are determined by means of a filtration test, in accordance with the internal Süd-Chemie standard methods. With this test, the time is measured which a predetermined quantity of a bleaching earth oil- suspension requires for filtration.
Average samples are taken from all Tonsil® deliveries which are dispatched, by means of an automatic sampling system. These samples are run through the physical and chemical inspections of our quality control process, and only after careful examination of these date is the product approved for dispatch.
If desired, our customers receive a quality certificate with every consignment, which, as a rule, contains the following examination features:
1 Humidity (water content at 110 °C, 2h)
1 pH (10% suspension filtered)
1 Dry screening residue to 63 micron
1 Filtration time
1 Apparent bulk density (indicative)
The bleaching activitiy is determined as a matter of routine, as an especially important parameter for assessing the quality of our various different Tonsil® bleaching earths.
The bleaching activity of a specific Tonsil® quality should, as far as possible, remain constant. Guaranteeing this is one of our most important tasks. To determine whether this is being done,
bleaching tests are carried out for comparison with a standardised bleaching earth and the bleaching earth which is to be tested. To do this, within the scope of our international Süd-Chemie standard methods, a test oil is used, difficult to bleach and defined according to acid value and colour. The colours of the bleached oils can be compared colorimetrically with one another, and tested in the spectral photometer; this ensures that even the smallest colour variation can be reliably detected. In order to achieve a better assessment of the bleaching activity for our client, the comparison bleaching tests are often also carried out with the corresponding oil samples from our customers’ refineries.
The assessment of these quality tests, over many years, provides an impressive picture of the consistency of quality of our Tonsil® bleaching earths, and of the considerable fluctuation in the oil qualities of the different oil seeds.
The humidity of the Tonsil® bleaching earths is adjusted to 3-9% in our combined grinding and drying facility, and checked on every single consignment at the goods dispatch inspection. If specially requested, a determination can also be made using the Karl Fischer titration method, which, in terms of precision of measurement, provides largely identical results to the drying method.
As a matter of routine, the acidity of our Tonsil® bleaching earths is also inspected. To do this, the residual acid content and the pH value of the aqueous extract is determined. Usually, the pH value is located in the weak acidic range, special qualities may deviate from it.
Particle size distribution and filtration properties The particle size distribution of Tonsil® bleaching earths is determined by means of gentle air-jet screening in the size range from 25 to 150 microns, using standardised screens. The determination of the very fine particles, of less than 25 micron, filtration performance in modern pressure leaf filters. Many filter manufacturers have designed their filter systems on the basis of our Tonsil® Optimum 210 FF bleaching earth, and linked their guarantee declaration regarding the systems to the use of FF qualities of Tonsil® bleaching earths.
Apparent bulk density
The apparent bulk density of our Tonsil® bleaching earths depends on the raw material used, the degree of acid activation and the particle size distribution, and under normal circumstances is between 300 and 800 g/l for powder material and 500 – 1,000 g/l for granular bleaching earths. For the majority of Tonsil® bleaching earths in bulk (silos, trucks, railway wagons, etc.), and for their storage in a silo facility. This information is included on each of our quality certificates.