JAIC 1981, Volume 21, Number 1, Article 2 (pp. 43 to 48)
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Journal of the American Institute for Conservation
JAIC 1981, Volume 21, Number 1, Article 2 (pp. 43 to 48)

NOTES ON A PRESSURIZED SYSTEM FOR PRODUCING MAGNESIUM BICARBONATE SOLUTIONS

Randall Couch



4 MAGNESIUM HYDROXIDE

WE FIRST EXAMINED THE EFFECT of variations in the quantity and quality of our starting material. The concentration of magnesium bicarbonate solutions varies proportionally with the amount of magnesium hydroxide used. In an eight-gallon volume, a minimum of 176.3 grams of magnesium hydroxide is necessary to produce a 0.1 M solution.5 A solution of this concentration was not regularly employed at NEDCC because solutions of lower concentration were often too cloudy for immediate use.

Reasons for this cloudiness were investigated. Although about one percent of magnesium hydroxide powder is expected to be insoluble due to impurities,6 it was not certain that the observed cloudiness could be attributed to this factor alone. Another possible cause of cloudiness was the age of our magnesium hydroxide supply. Since this material tends to convert to the basic carbonate on exposure to air, some contamination could occur under practical storage conditions. If the slower-dissolving carbonate was present in any quantity, a cloudy solution would result. A fresh shipment of magnesium hydroxide, however, made no appreciable difference in clarity. Solutions made from it remained cloudy and no change in concentration was noted. Therefore we concluded that no practical improvement could be made based on the quality of the magnesium hydroxide.


Copyright 1981 American Institute of Historic and Artistic Works