  We report the detection, for the first time, of HCO+ (J=1-0) emission as well
as marginal CO (J=1-0) emission toward the planetary nebula (PN) K3-35 as a
result of a molecular survey carried out toward this source. We also report new
observations of the previously detected CO (J=2-1) and water maser emission, as
well as upper limits for the emission of the SiO, H13CO+, HNC, HCN, HC3OH,
HC5N, CS, HC3N, 13CO, CN, and NH3 molecules. From the ratio of CO (J=2-1) to CO
(J=1-0) emission we have estimated the kinetic temperature of the molecular
gas, obtaining a value of ~20 K. Using this result, we have estimated a
molecular mass for the envelope of ~ 0.017 M_Sun, and an HCO+ abundance
relative to H_2 of 6 X 10^-7, similar to the abundances found in other PNe.
K~3-35 is remarkable because it is one of the two PNe reported to exhibit water
maser emission, which is present in the central region as well as at a distance
of $\simeq$ 5000 AU away from the center. The presence of molecular emission
provides some clues that could help to understand the persistence of water
molecules in the envelope of K 3-35. The HCO$^{+}$ emission could be arising in
dense molecular clumps, that may provide the shielding mechanism which protects
water molecules in this source.
