Safety of silica gels with color indicators

It depends on the color indicator. Pure silica gel, molecular sieve and aluminum oxide are not classified as hazardous substances according to European Union legislation (Regulation EC No. 1272/2008). They do not require labeling according to EC Directive (67/548/EEC or 1999/45/EC). Silica gel is not classified as hazardous to health or the environment. Furthermore, they are non-flammable and chemically stable. No ecological problems are to be expected if handled and used properly.

If these adsorbents are used in aeration dryers, a color indicator is often applied. Especially with silica gels, various color changes are available that indicate the water content above a certain weight percentage. Some color indicators are classified as toxic and hazardous to health. Such color indicators also make these silica gels subject to labeling requirements.

Blue silica gel with color indicator cobalt(II)chloride

Cobalt(II) chloride (CoCl2) was very often used as a color indicator in the past. When the silica gel has bound water, this indicator changes color from blue to pale pink to whitish; the hexaaqua complex ([Co(H2O)6]Cl2) is formed. On drying, this process is reversible.

To this day, aeration dryers with “blue gel” are used. And this despite the fact that cobalt(II) chloride is considered to be carcinogenic as well as teratogenic and possibly mutagenic. The substance was again included in the candidate list of substances of very high concern (SVHC) by the ECHA (European Chemicals Agency) on October 28, 2008. The entry was amended on June 20, 2011 to include the reproductive toxic properties.

Taking this into account, the EEA (Electricity Engineers’ Association of New Zealand), for example, in a handling recommendation issued to its members in April 2013, recommends the use of silica gel orange to minimize risks.

Silica gel orange with organic indicator

Silica gels with heavy metal-free indicators have been produced and used for several years. The indicators used are pH indicators, which belong to the organic dyes. These have the character of weak acids or bases. Thereby acid has a different color than the corresponding base. For silica gels, this means that the pH increases with increasing water content and the color changes from orange to green or white. This process is reversible and can be repeated.

When using Silica Gel Orange, attention must be paid to the indicator used and, in particular, the amount of it. For example, Silica Gel Orange is sold with approx. 2.5% methyl violet. This proportion of methyl violet is a cause for concern and is also classified as toxic. Manufacturers of silica gels who attach importance to sustainability as well as health-compatible and environmentally friendly products refrain from using such compositions. Among the pH color indicators, there are also harmless indicators. Since the color indicator has a significant influence on the quality of the silica gel, the exact mixing ratio is not specified by manufacturers with a claim to quality.

It is important that manufacturers provide essential information on use and compatibility in their safety data sheets in accordance with Regulation (EC) No. 1907/2006. must.

Subject to labeling hazardous substances unter REACHCobalt(II)chlorideMethyl violetNone
HazardsMay cause cancer by
inhalation.
Toxic hazard designation
Harmful to aquatic
organisms, may cause
long-term adverse effects.
Not classified as
dangerous.
HandlingUse only in well-ventilated
areas. Do not breathe
vapors and dust.
Keep container tightly
closed.
Open container with care
and handle.
Avoid formation of dust
and aerosols.
Toxicological informationKnown carcinogen product.The usual precautionary
measures for handling
chemicals should be
followed.
The usual precautionary
measures for handling
chemicals should be
followed.
EcotoxicityMay cause long-term
adverse effects.
Do not flush into surface
water or sanitary sewer
system.
May cause long-term
adverse effects.
Do not flush into surface
water or sanitary sewer
system.
May cause long-term
adverse effects.
Do not flush into surface
water or sanitary sewer
system.
LegislationR22 – Harmful if swallowed.
R42/43 – Prevent
sensitization by inhalation
and skin contact.
R49 – May cause cancer by
inhalation.
R50/53 – Very toxic to
aquatic organisms, may
cause long-term adverce effects.
R22 – Harmful if
swallowed.
R40 – Evidence of a
carcinogenic effect.
R41 – Risk of serious
damage to eyes.
R50/53 – Very toxic to
aquatic organisms, may
cause long-term adverse
effects.
None