ISO 57:1975 pdf free
ISO 57:1975 pdf free.Bleached lac – Specification
This International Standard covers bone-dry bleached lac, an intermediate surface-dry (ai-dry) bleached lac, and wet bleached lac, the three differing in their requirements in the moisture content. No distinction is sought to be introduced between bone-dry, kiln-dry or vac-dry bleached lac or between the various designations of the intermediate type covering dried, crushed hanks, or flats in granules or flakes, or between wet-bleached lac in hank, bar or any other form. Only three conditions, i.e, bone-dry, surface-dry (air-dry) and wet, and two types in each condition, namely a) regular bleached lac (cloudy or waxy), and b) refined bleached lac (transparent or wax-free), more briefly indicated as “regular” and “refined” are recognized.
No limit has been specified for the chlorine content of bleached lac. Normally the chlorine content of bleached lac varies between 1,5 and 4,5 % in moisture-free material, but ISO/TC 50 has decided to place it on record that it is desirable to maintain it at a low value (say at 3 %,maximum).
Likewise, no limit has been specified for the acid value of bleached lac. This depends on the methods of bleaching. The acid value of a good bleached lac is normally between 65 and 100 on the moisture-free material. ISO/TC 50 considers it desirable to retain the acid value at as low a value as possible below 105.
The mesh sizes of sieves given in this International Standard have been indicated in terms of aperture dimensions, and a note, giving number designations of approximately equivalent sieves according to ISO 565 and according to the national standards of the U.S.A., the United Kingdom, France, Germany and India, has been added for the sake of convenience.
For the purpose of deciding whether a particular requirement of this International Standard is complied with, the final value observed or calculated, expressing the result of test or analysis, shall be rounded off to the same number of places as that in the specified value; it being always understood that the analyst will carry out his determination to at least one place more than in the specified value.ISO 57 pdf download.
