The interstellar abundance of titanium.

From spectrograms of 13 stars taken by us combined with data for eight further stars reported by others, we have determined the column densities of Ti ii for 11 stars and upper limits for 12 stars. Observations and theory can be used to show that little or no Ti I or Ti iii is expected to be present in interstellar gas. The derived Ti/H ratios range from 3 x 10- to 3 x 10-10, which is a deficiency of titanium by a factor from 20 to 200. Data and arguments are presented to show that much of the interstellar titanium and calcium is probably locked up in the grains. Subject headings: abundances - interstellar matter