ISO 1620-1976 rus PDF

Full title and description

ISO 1620:1976 — Cryolite, natural and artificial — Determination of silica content — Reduced molybdosilicate spectrophotometric method. Specifies a wet-chemistry spectrophotometric procedure for measuring silicon dioxide in natural and synthetic cryolite materials (applies to products with specified NaF/AlF3 molar ratios and low P2O5 content). The standard is published by the International Organization for Standardization (ISO). Note: the ISO catalogue indicates no Russian-language version is available.

Abstract

This standard describes a reduced molybdosilicate spectrophotometric method for determining silica in cryolite (natural and artificial). The procedure involves alkaline fusion, dissolution in nitric acid to a controlled acidity, formation of molybdosilicate, selective reduction in the presence of tartaric acid and photometric measurement near 815 nm. It is intended for cryolite materials with phosphorus pentoxide content not exceeding 0.02 % (m/m).

General information

• Status: Published (confirmed as current in ISO catalogue periodic review).
• Publication date: September 1976 (ISO edition 1).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 71.060.50 (Chemistry of inorganic compounds / cryolite and related materials).
• Edition / version: Edition 1 (ISO 1620:1976).
• Number of pages: Typically published as a short technical specification — sources report 5 pages (other catalogues list up to 8 pages depending on reprints/translations).

Scope

Gives a standardized analytical method for the quantitative determination of silica (SiO2) in natural and artificial cryolite materials. The method applies where the molar ratio NaF/AlF3 is approximately between 3 and 1.7, and where P2O5 content does not exceed 0.02 % (m/m). The procedure covers sample fusion, controlled acidification, formation and reduction of molybdosilicate and spectrophotometric measurement under defined conditions.

Key topics and requirements

• Alkaline fusion of test portion using a sodium carbonate and boric acid mixture to decompose the sample.
• Dissolution of the fused mass in excess nitric acid and adjustment of acidity (pH ≈ 0.7–0.9) prior to color development.
• Formation of oxidized (yellow) molybdosilicate under defined reagent concentrations, temperature and time.
• Selective reduction of the molybdosilicate in the presence of tartaric acid, producing the colored reduced species measured spectrophotometrically.
• Photometric measurement at about 815 nm to quantify silica concentration against calibration standards.
• Applicability limits: recommended for cryolite with specified NaF/AlF3 ratio and low P2O5; other interferences or matrix differences may require alternative methods or validation.

Typical use and users

Analytical and quality-control laboratories in the aluminium and fluoride-chemicals industries; producers and users of cryolite (e.g., fluxes and aluminium smelting inputs); standards bodies and test laboratories performing composition verification and acceptance testing of cryolite materials. Also used by research laboratories focusing on inorganic raw materials and process control where silica impurity quantification is required.

Related standards

Related ISO items include ISO 1619 (sample preparation and storage for cryolite) and the earlier working draft ISO/R 1620:1970 which ISO 1620:1976 replaced or consolidated. National and regional test method standards for silica determination and cryolite testing may complement this ISO method.

Keywords

cryolite; natural cryolite; artificial cryolite; silica; SiO2; molybdosilicate; spectrophotometry; analytical method; alkaline fusion; sodium carbonate; boric acid; tartaric acid; aluminium industry.

FAQ

Q: What is this standard?

A: ISO 1620:1976 is an international standard that specifies a reduced molybdosilicate spectrophotometric method for determining silica content in natural and artificial cryolite.

Q: What does it cover?

A: It covers sample decomposition by alkaline fusion, dissolution and acidity control, formation and selective reduction of molybdosilicate, and spectrophotometric measurement (around 815 nm) to quantify SiO2 in cryolite within defined compositional limits.

Q: Who typically uses it?

A: Quality-control and analytical laboratories in the aluminium and refractory/flux industries, material suppliers, test houses and researchers working with cryolite and related fluoride materials.

Q: Is it current or superseded?

A: ISO’s catalogue shows ISO 1620:1976 as published and indicates periodic confirmation; the entry was reviewed and the published version remains in force (confirmed in ISO’s lifecycle records). Users should check the ISO catalogue or their national standards body for any later amendments or replacements.

Q: Is it part of a series?

A: It is part of the set of ISO standards dealing with cryolite and related test methods (see nearby ISO entries such as ISO 1619). It follows earlier working documents (ISO/R 1620) and sits among other analytical standards for inorganic materials.

Q: What are the key keywords?

A: Cryolite, silica, SiO2, molybdosilicate, spectrophotometric method, alkaline fusion, aluminium industry.