Notes on fluorine

Conclusion

1. Instead of being present in trifling amounts, fluorine is evidently present in amounts equal to or greater than chlorine.

2. It is a reasonable inference that the average content of the igneous rocks is about three to four hundredths of a percent. The average content for all specimens analyzed is 0.064% but this figure is invalidated by the fewness of the analyses and the too great selection of the specimens studied.

3. We find that the fluorine retained in lavas is not too reliable an index of the amount which may have been present at the time of eruption. We are as yet ignorant of the particular indications of the former presence of this elusive element; the trail is still blind.

4. Now that an easy and accurate method for its determination is available fluorine must be included among the elements which the volcanologist is watching. There is as yet no simple, easy field test, although one can readily be devised. The collection of gases in such a manner that fluorine can be determined quantitatively offers difficulties but not serious ones.

The known effect of fluorine on the viscosity of silicate melts and as a mineralizer now comes into the range of the volcanologist’s vision as a factor to be studied.