5 Conclusions

The following general conclusions can be drawn:

i) We present new polarization measurements of ten symbiotic stars and analyze the wavelength dependence of both the percentage of polarization and the position angle. We find that eight objects show temporal variations vs wavelength, indicating that intrinsic polarization is present (V748 Cen, Hen 1103, CL Sco, AR Pav, FN Sgr, RR Tel, CD  $-43^{\circ }$14304 and AG Peg). Four out of these polarized stars did not possess polarization data before the present study (V748 Cen, Hen 1103, CL Sco and FN Sgr). KX TrA and Hen 1761 represent two cases of unpolarized symbiotics.

ii) Except for RR Tel, 7 of the polarized objects are S-type symbiotics. If the polarization is produced mainly by dust particles, the circumstellar envelope surrounding the cool component in S-type symbiotics contains grains different from those producing infrared excess.

iii) We present wavelength dependences of $P(\%)$ decreasing monotonically from blue to infrared; decreasing in opposite sense; peaking in some particular wavelength or presenting a dip in the visual and then increasing to blue and red. Different dependences can be observed for each star along the time. Moreover, no conclusive correlation between the behavior of polarization and position angle can be drawn.

iv) The time scales of variations are of the order of several days or months. v) In five cases (V748 Cen, CL Sco, AR Pav, CD  $-43^{\circ }$14304 and AG Peg) the orbital period of the binary is known and a correspondence between the orbital phase and the variable behavior of the polarization might be suggested in some of them. However, the maxima and minima in the polarization are produced at different configurations of the components with respect to the observer. Consequently, the source of light and the scattering regions are not the same in all the binary systems. It is necessary to extend the observations in time in order to cover the orbital cycles.

vi) Several scattering regions associated with gas stream, accretion disks, Mira component or extended nebulae could be present and different sources of intrinsic polarization should be considered in the same object.