Calcium imbibed

Table II shows the calcium content in paper from the chemical feeder process. With the addition of 9.2 ppm Ca in DI water, the treated newsprint papers calcium content doubled in comparison with the control. The treated Foldur Kraft paper contained three times more calcium than did the unwashed paper. The more calcium that was added in the DI water, the higher the amounts of calcium absorbed in the papers during the washing and deacidification process. However, the absorption of calcium in the paper reached a saturation point. This is the reason why newsprint and Foldur Kraft papers that are treated with 36.4 ppm Ca in the Dl-Ca water imbibed the same amount of calcium as the papers washed with 112.8 ppm Ca in the Dl-Ca water.

Barrow s examinations of stable, old papers found that most had a significant calcium or magnesium carbonate content. Today, some of the best aqueous deacidification treatments introduce these compounds. There are several popular materials used for aqueous deacidification, one of these is calcium hydroxide solution (lime water). Calcium hydroxide is not very soluble in water a saturated solution contains 1.85 gL 1 in ambient conditions and has a pH of 12.4 which is quite high. Severely degraded papers are suspected to undergo alkaline hydrolysis and some inks can bleed at such a high pH. While the paper is in the solution, the acids are neutralised. When treated paper is removed from the solution, the imbibed calcium hydroxide reacts with carbon dioxide in the air to form stable calcium carbonate. If the object has a very black area, e.g. as in some mezzotint prints, the dried precipitated carbonate may sometimes be visible as a white bloom, however, usually it is not seen. The eventual pH of the paper is in the range 8.0-9.0. 

An in vitro calcification study was performed on lipid-imbibed Biomer samples to study the effects of surface adsorbed/absorbed lipids on the formation of surface calcium salts in vitro. A high calcium-buffered physiological medium was developed, as described in Ref. 21, to study the effects of imbibed surface lipids on calcium deposition. To a standard dialysate solution (Diasol Low Calcium-120, Travenol Laboratories) was added 1.5mM calcium chloride and potassium phosphate. The solution pH was adjusted to 7 with dilute aqueous sodium hydroxide. Lipid-exposed polymer strips and polymer control strips were soaked in the solution for 1 week, and were subsequently dried and weighed. 

The functional properties are illustrated by the watCT-qjrotein interactions of soy protein isolate (SPI). SPI, with high solubility, or excessive thermally induced insolubiUzation, or compact calcium-induced aggregates, gives rise to low water-imbibing capacity (WIC) values. The highest WIC results from the balance between intermediate... 

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