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Adopted opinions and previous consultations on applications for authorisation

Adopted opinions and previous consultations on applications for authorisation


This page provides further information on the applications for authorisation or review reports, which have undergone consultation. The applications for authorisation are in the opinion development phase until the final opinions of the Committees for Risk Assessment and Socio-economic Analysis have been adopted and sent to the European Commission. The European Commission's decision-making process can be followed through the comitology register, where further information is published about the REACH Committee's past and upcoming meetings.

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Substance Details

Sodium dichromate
EC Number
CAS Number
Entry Nr in Annex XIV
Use name
Use of sodium dichromate as an additive for suppressing parasitic reactions and oxygen evolution, pH buffering and cathode corrosion protection in the electrolytic manufacturing of sodium chlorite.
Broad information on use applied for (conditions of use and function)
Sodium dichromate (EC number: 234-190-3, CAS number: 10588-01-9 (anhydrous), 7789-12-0 (dihydrate)) is a process chemical used in the manufacture of sodium chlorate. More precisely, sodium dichromate is used as an additive for suppressing parasitic reactions and oxygen evolution, pH buffering and cathode corrosion protection in the electrolytic manufacture of sodium chlorate with (or without) subsequent production of chlorine dioxide or sodium chlorite. Sodium chlorite is a powerful oxidant which is sold mainly for use in potable, industrial and waste water treatment for the elimination of bacteria, slime, mould and algae, for the reduction of unpleasant taste and odour and to contribute to the removal of iron and manganese in non-treated water.
Sodium chlorite is produced in several steps, the first step being production of sodium chlorate and the second step being conversion of sodium chlorate to chlorine gas and chlorine dioxide by addition of hydrochloric acid. Sodium chlorate is produced by electrolysis of sodium chloride brine, yielding hydrogen gas as co-product. Electrolysis of sodium chloride brine is performed under pH conditions where the chlorine from the anode remains combined with sodium hydroxide in the form of sodium hypochlorite, which is then converted into sodium chlorate and chloride. The resulting solution, rich in sodium chlorate and with a lower content of chloride, is fed in the “chlorine dioxide generator” (a closed reactor) where chlorine dioxide and chlorine are formed by addition of hydrochloric acid. Sodium dichromate quantitatively remains in the reaction liquor inside the chlorine dioxide generation reactor and is transferred back to the sodium chlorate production unit together with the remaining (non used) sodium chlorate.

Sodium dichromate plays four interlinked roles in the sodium chlorate production process: 1. it acts as a pH buffer, 2. it suppresses the production of oxygen, thus preventing the creation of explosive mixtures with hydrogen, 3. it passivates the steel cathodes, thus protecting them from corrosion, and 4. it increases energy efficiency and the overall efficiency of the chlorate process by suppressing certain parasitic reactions at the cathode. The suppression of cathode reactions appears to be by far the most critical task for sodium dichromate.

The applicant, SOCIETA' CHIMICA BUSSI S.P.A is to build a new plant to produce Sodium Chlorite for use in the water treatment sector. The SCB plant has obtained the requisite building permits and financing and the plant is expected to be ready for operation towards the end of 2019.

Annual tonnage used: 0.1-2 tonnes per year
Review period requested: 12 years
Use applied for number in application for authorisation
Broad information on use applied for (Use descriptor system)
Sector of end use (SU): 8
Environmental release category (ERC): 4
Process category (PROC): 3, 8a, 8b, 15
Product category (PC): Other: processing aid
Article category related to subsequent service life (AC): N/A
Technical Function: antiscaling agent, corrosion inhibitor
Summary table of RMMs and OCs (non confidential)
Section 9 and 10 of the CSR (original and updated, if available) (non confidential)
Analysis of Alternatives (non confidential report)
Substitution Plan (non confidential summary)
Socio-Economic Analysis (non confidential report)
Joint Analysis of Alternatives and Socio-Economic Analysis (non confidential report)
Explanatory note
Additional information
Application type
Opinions adopted
Other consultations on the same/ similar use
Comments submitted to date
No comments received
Response to comments by applicant
Responses to RAC and SEAC requests by Applicant(s) (non confidential)
Compiled RAC and SEAC opinions
Minority positions
Adopted commission decision (OJ summary)
Authorisation decision

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