Remarks concerning calcium hydride
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8.
Remarks concerning calcium hydride
Calcium hydride is reported as dangerous goods in the material safety data sheet.
This classification refers to large amounts, so that the recommended precautions to exposure
are valid over any length of time with any great amount (e.g. filling a silo or the like)
About the toxicity of calcium hydrid:
Calcium hydride reacts with water immediately to calcium hydroxide (slaked lime) and
hydrogen. In this reaction, heat is released. In minor amounts, which are used in the
measurement with the HydroTracer, damage by heat development is virtually impossible.
In an aqueous solution of calcium hydroxide reacts alkaline (pH up to about 11). The
resulting solution is an irritant and skin contact should be avoided. From the overall experience
it is known as calcium lime mortar. In the food industry, calcium lime is added as an acidity
regulator for foods and in the EU as a food additive called E 526 approved without maximum
limit (quantum satis) generally for food.
The resulting hydrogen is produced also as a metabolite in the human body and is non-toxic.
About the explosion capacity of calcium hydride:
Hydrogen is produced by the reaction of calcium hydride with water. In air hydrogen is
explosive at concentrations of 4% (detonating gas reaction). Since only small amounts of the
reagent used (maximum of 75g per bottle) it is practically impossible to create a flammable
mixture with air in a room. The very high volatility of the hydrogen gas prevents locally higher
concentrations formed in the air.
Disposal of the used reagent:
The reagent used in the HydroTracer is still largely reactive after the measurement. By
exposure to air, it can react slowly with atmospheric moisture to calcium hydroxide
(approximately 1-2 hours). Subsequently calcium hydroxide reacts with the carbon dioxide of
the air to calcium carbonate (limestone) and can then be disposed of with household waste.
Conclusion:
When dealing with calcium, it is crucial that the amount used is minimized. Ingestion inhalation
and contact with the mucous membranes should be avoided to prevent irritation. The minor
potential of harm is also caused by the small amounts (about 0.1 g) which are advised in the
manual. The chemical hazard corresponds to that of slaked lime.
In normal use no risk of explosion due to hydrogen gas.
