Grades. Sodium Metabisulfite

Transcription

1 Technical Leaflet M 5323 e April 1999 (rws) Sodium Metabisulfite Grades Supersedes issue December 1994 Sodium Metabisulfite Sodium Metabisulfite PHOTO GRADE Sodium Metabisulfite FOOD GRADE Sodium Bisulfite Solution 38 40% Sodium Bisulfite Solution FOOD GRADE Reducing agents for the chemical, pharmaceutical, photographic and textile industries and as food additives. Auxiliary for water and sewage treatment Bleach for the paper and pulp industry Auxiliary for the film and photographic industry Ensiling agent Preservative Basic Chemicals

2 Sodium Metabisulfite Grades Chemical names Commercial names Sodium metabisulfite, sodium disulfite, sodium pyrosulfite Sodium Metabisulfite Sodium Metabisulfite PHOTO GRADE Sodium Metabisulfite FOOD GRADE Chemical formula Molar mass g CAS No EINECS No Chemical name in aqueous solution Sodium hydrogen sulfite, sodium bisulfite Commercial name Sodium bisulfite solution 38 40% Sodium bisulfite solution FOOD GRADE Chemical formula NaHSO 3 Molar mass g CAS No EINECS No Grades and packaging available Sodium Metabisulfite, Sodium Metabisulfite FOOD GRADE and PHOTO GRADE can be purchased in 50 kg and 25 kg PE bags. They can also be supplied in Big Bags. The products are supplied on disposable pallets which can be wrapped, if requested by the customer. Sodium Bisulfite Solution 38-40% and FOOD GRADE are delivered only in rail tank cars. Properties Sodium Metabisulfite and Sodium Metabisulfite FOOD GRADE and PHOTO GRADE are microcrystalline powders with a faint odour of sulfur dioxide; their bulk density lies between 1.0 and 1.2 kg/l. Sodium Bisulfite Solution 38 40% and FOOD GRADE are clear, slightly yellowish liquids with a strong odour of sulfur dioxide, and ph values between 3.9 and 4.4. Sodium metabisulfite decomposes at temperatures above 120 C. If the containers in which it is stored are not tightly closed, it rapidly absorbs moisture and is oxidized. The amount of water absorbed by the product in closed containers depends on the rate of diffusion, which in turn depends very much on the temperature and relative humidity. Under unfavourable storage conditions, this may lead to the formation of hard aggregates in the product, i.e. caking. All the grades of sodium metabisulfite are readily soluble in water. In aqueous solution they are in the form of sodium bisulfite, i.e. in the same form as in our products Sodium Bisulfite Solution 38 40% and FOOD GRADE. However, the solution prepared in this way is of higher purity. Sodium bisulfite solutions undergo oxidation on standing in air. 2

3 Table 1 Density and composition of sodium bisulfite solutions of various concentrations NaHSO 3 NaHSO 3 Amount of Density Concentration content Required for Preparation (g/100 g) (g/100 ml) (g/100 ml) (g/100 ml) Temperature, C Concentration, g/100 g Fig. 1 Solubility of sodium metabisulfite in water 3

4 Product specifications The values and test methods stated in the product specifications below were valid when this Technical Leaflet was drawn up, but subsequent changes are possible. The current product specifications are available on request. The only values which are binding are those in the relevant specification sheets then provided. Sodium Metabisulfite Property Unit Typical Value Limit Test method (g/100 g) 98.0 min ANSI PH SO 2 (g/100 g) 66.0 min calc. ph (5% solution) < ISO (E) NaCl (mg/kg) 20 max. 50 RCA/Q-IC-01 Heavy metals as Pb (mg/kg) max. 10 AES BASF M 91/41 Iron (mg/kg) < 5 max. 10 AAS BASF M 90/5 SO 3 + SO 4 remainder calculated Product specification RCA-NDS-E, Rev. 1, 01 Feb Sodium Metabisulfite PHOTO GRADE Property Unit Typical Value Limit Test method (g/100 g) 98.7 min. 98 ANSI PH SO 2 (g/100 g) 66.5 min. 66 calc. ph (5% solution) ISO (E) O 3 (g/100 g) max RCA/Q-S-063 NaCl (mg/kg) 20 max. 30 RCA/Q-IC-01 Heavy metals as Pb (mg/kg) max. 10 AES BASF M 91/41 Iron (mg/kg) < 3 max. 5 AAS BASF M 90/5 Insoluble matter (g/100 g) < 0.01 max. 0.5 ANSI PH SO 3 (g/100 g) < 1 max. 1.5 ISO (E) SO 4 remainder calculated Product specification RCA-NDSPG-E, Rev. 1, 01 Feb

5 Sodium Metabisulfite FOOD GRADE Property Unit Typical value Limit Test method g/100 g 98.0 min ANSI PH SO 2 g/100 g 66.0 min calculated ph (10% solution) < RCA/Q-S-066 NaCl mg/kg 20 max. 50 RCA/Q-IC-01 Heavy metals as Pb mg/kg max. 10 AES BASF M 91/41 Iron mg/kg < 3 max. 5 AAS BASF M90/5 Arsenic mg/kg < 0.1 < 1 AAS BASF M90/7 Lead mg/kg < 0.1 < 1 AAS BASF M90/5 Copper mg/kg < 1 AAS BASF M90/5 Mercury mg/kg < 0.03 < 0.1 AAS BASF (cold vapour) Selenium mg/kg < 0.1 < 1 AAS BASF M90/8 Zinc mg/kg < 1 AAS BASF M90/5 SO 3 + SO 4 remainder calculated Product specification RCA-NDSFG-E, Rev. 1, 01 Feb Sodium Bisulfite Solution 38 40% Sodium Metabisulfite FOOD GRADE is approved in the EU according to EC directive 96/77/EC (of Dec. 2, 1996) annex III part B (E No.: 223), for use as a preservative and antioxidant in the foodstuffs listed therein, up to the stated maximum amounts. The product also complies with the requirements listed for sodium metabisulfite in the Food Chemical Codex, 4th edition (FCC IV) on page 369. These requirements apply to its use in the foods sector in North America, parts of South America and in many countries outside the EU. Finally, this product also meets the requirements listed in the Compendium of Food Additive Specifications of the FAO/WHO Joint Expert Committee on Food Additives (JECFA), Add. 61, June 1998, page 143. Property Unit Typical value Limit Test method NaHSO 3 (g/100 g) calculated SO 2 (g/100 g) 24.0 min RCA/Q-S-054 Density (at 20 C) (kg/l) DIN (Similar) Iron (mg/kg) < 20 max. 50 AAS BASF 90/5 Product specification RCA-NSL-E, Rev. 3, 06 Feb

6 Sodium Bisulfite Solution FOOD GRADE (E 222) Property Unit Typical Value Limit Test method NaHSO 3 (g/100 g) RCA/Q-S-054 SO 3 (g/100 g) max. 0.7 RCA/Q-S-054 SO 4 (g/100 g) max. 1.5 RCA/Q-IC-01 Cl (mg/kg) max. 150 RCA/Q-IC-01 Density (kg/l) Based on DIN ph (as is) Based on DIN Fe (mg/kg) < 10 max. 20 AAS BASF M90/5 Heavy metals as Pb (mg/kg) < 2 (each) AES BASF M91/41 (Cd, Cu, Cr, Pb, Zn) As (mg/kg) < 1 AAS BASF M90/7 Se (mg/kg) < 1 AAS BASF M90/8 Hg (mg/kg) < 0.05 AAS (cold vapour) Product specification RCA-NSLFG-E, Rev. 3, 06 Feb Chemical properties Sodium metabisulfite is a strong reducing agent in aqueous solution. It binds the oxygen dissolved in water and must therefore not be discharged untreated into rivers and lakes, because it may seriously disrupt animal and plant life. Because aqueous solutions are acidic, suitable materials for pipelines and tanks include Remanit (German material No ), PP, PE and PVC. The only resistant hard rubber types are those with a high graphite content. Detailed information on materials can be found in the DECHEMA materials table. Any contact with nitrites and nitrates and with oxidizing agents must be avoided because the reaction can be violent in some circumstances. Application In the chemical and pharmaceutical industries for various purposes, e.g. As a reducing agent, for purifying and isolating aldehydes and ketones, for destroying waste bromine, in the preparation of dyes. In drinking water treatment to remove excess chlorine. In special cases to remove oxygen from boiler feed water. In the treatment of wastewater, e.g. from electroplating plants, to neutralize chromic acid; to remove excess chlorine in the neutralization of cyanide. For cleaning and bleaching wool, jute and other vegetable fibres. In textile dyeing and printing to prepare indigo vats and to solubilize other dyes. For solubilizing tanning extracts. In the paper and pulp industry for bleaching ground wood. In the photographic and film industry for preparing developer solutions, for acidifying fixing baths. 6

7 For ensiling green fodder, for preserving foodstuffs (restricted use in accordance with the additives approval regulations, E223). Safety Biological effects All the sodium metabisulfite grades have a faint odour of SO 2 and irritate the eyes and respiratory tract. On contact with acids, they may evolve hazardous quantities of toxic SO 2 gas. In the water course, sodium bisulfite causes severe oxygen depletion and may therefore harm aquatic organisms. Further details can be found in our safety data sheets for the individual products. Safety advice Sodium metabisulfite is not included as a hazardous substance in Annex I of EC Directive 67/548/EEC. On the basis of the data available to us, the sodium metabisulfite products, including the PHOTO and FOOD GRADES, must be labelled as harmful with the hazard symbol Xn and, consequently, with the following R and S phrases: R 41 risk of serious damage to eyes R 37 irritating to respiratory system R 31 contact with acids liberates toxic gas R 22 harmful if swallowed 6 in case of contact with eyes, rinse immediately with plenty of water and seek medical advice. MAK for SO 2 : 2 ppm = 5 mg/m 3 TLV for SO 2 : 2 ppm = 5 mg/m 3 All grades of sodium metabisulfite fall under water hazard class 1. Storage and transport All sodium metabisulfite grades should be stored under cool and dry conditions. They are stable for six months if the storage temperature does not exceed 25 C and the relative humidity does not exceed 45%. If higher temperatures and/or higher humidities occur during storage, this may lead to a decrease in the SO 2 content and the ph of the aqueous solution. Similar effects are produced by wide variations in the storage temperature. The chemical changes may be accompanied by the formation of more or less hard agglomerates. Compression also causes caking for example if pallets are stacked on top of one another. Sodium Bisulfite Solution 38 40% and Sodium Bisulfite Solution FOOD GRADE have only limited stability: the solutions should be used up within a short time. Sodium metabisulfite may crystallize out at temperatures below 10 C. Safety data sheet Further information on the sodium metabisulfite grades and on Sodium Bisulfite Solution 38 40% and FOOD GRADE are to be found in the relevant Safety Data Sheets. Note The information submitted in this publication is based on our current knowledge and experience. In view of the many factors that may affect processing and application, these data do not relieve processors of the responsibility of carrying out their own tests and experiments; neither do they imply any legally binding assurance of certain properties or of suitability for a specific purpose. It is the responsibility of those to whom we supply our products to ensure that any proprietary rights and existing laws and legislation are observed. 7

8 BASF Aktiengesellschaft Marketing Grundchemikalien Petrochemikalien und Anorganika Ludwigshafen, Germany Printed in Germany