Cauterisation and Environment - HARKE Group

Imaging
The granules consist of about 60 % FeCl3 and 40 % chemically combined water and other substances. The
less content of active substances require a larger quantity use than the sublimate, the granules, however, do
not react exothermally when dissolving in water and therefore are much easier to handle. From 800 g
granules 56 % and 1 l water one gets about 1.4 litre 32 % solution.
1.1.3 Application
In an aqueous solution of ferric-III-chloride copper oxidizes to copper-II-chloride while the cauterisation
agent passes into the less inferior ferric-II-chloride. At a make-up quantity of about 35 w/w % FeCl3 the
maximum capacity of the cauterisation solution calculatively adds up to about 50 g copper / litre. The
cauterisation duration in a fresh solution of about 45°C under optimum machine conditions lies in the range
of about 2 seconds per 1 µm copper. It increases at first only slowly during the increasing consumption rate,
but before reaching the saturation point rapidly. The calculatively possible copper absorption is in practice
not being realised because of the decelerated cauterisation process and the increasing undercut of the
pattern plate. Shortly before the saturation limit the cauterisation agent tends to intensify the formation of
ferric- and copper chloride mud so that the cleaning process of the machine reasonably increases. The
increase of the cauterisation duration to about the double start value therefore marks the economically most
favourable moment to replace the cauterisation agent.
1.1.4 Environmental Compatibility
Used ferric-III-chloride solution cannot be recycled with justifiable costs. The possibility to dilute the solution
by adding hydrochloric acid and at the same time to delay the starting mud formation is in practice not being
used because this process will only be effective for a short time. An imaginable point for recycling according
the latest legal situation would only be the acid concentration or the precipitation of the heavy metals from
the solution and their afterwards smelting. According experience this recycling possibility, however, is only
being met to a limited extent. Failing other alternatives the used solution has to be disposed as hazardous
waste.
In order to avoid a contamination of the workplace by cauterisation vapours, sufficient room ventilation is
necessary when using ferric chloride. The aerosol formation especially appearing in spray cauterisation
machines may lead to mucous membrane irritation. Additionally cauterisation vapours corrosively effect
metal objects in the room strongly.
1.1.5 Evaluation
Cauterisation and Environment
The handling of ferric-III-chloride in form of granules is unproblematic. The use of the sublimate is subject to
a strict due diligence when newly preparing the caustic solution. The sublimate is recommended because of
its productiveness and unproblematic cauterisation behaviour for the use in often utilised or quasi continuous
used laboratories. With reference to the hazardousness of the real ferric-III-chloride it has to be mentioned in
the margin that it is being used in for instance waste water treatment plants as flocculants. Because of the
possible copper content in the consumed solution it has, however, to be categorized as hazardous waste.
© Aicello Chemical Europe - Xantener Str. 1 -45479 Mülheim an der Ruhr - Matthias Stange, Phone: +49 (0)208 / 3069 1530, Mail: sta@harke.com