21. The fort is made of stones rich in iron content which protects it from cannon attacks. 22. It is thought to be one " strongest of tonics " for its high iron content . 23. The water's excessive iron content meant that it could not be used as effectively as hoped. 24. The blue-grey colour is provided by its iron content , enclosed to a large extent in pyrites. 25. He said the iron content would be worth only about 14, 500 pesos ( dlrs 584 ). 26. The iron content is linked with the slag composition, the others elements are taken in the metal. 27. However, during the rainy season, the iron content though high, was found to be within permissible limits. 28. Pure magnesium tremolite is creamy white, but the color grades to dark green with increasing iron content . 29. Certain properties such as the iron content may be controlled, changing the thermal emissivity properties of glass. 30. Iron substitutes for magnesium in variable amounts leading to the more common biotite with higher iron content .
