In our previous experiments we have investigated the surface properties of liquid 3He - 4He mixtures by neutron reflection. We have shown that in broad temperature range there is an increased concentration of 3He atoms near the liquid surface. At low temperature the neutron adsorption increases significantly which might be an indication of the formation of Andreev states although the shape of curves does not change very much which may mean that the 3He layer is very thin ~ 10 Angstrom. However before publishing these fascinating results we need to prepare another experiment with 4He of highest purity. It will give us an opportunity to compare experimental data with the neutron reflectivity model in extreme case of pure 4He. We also need to reproduce some of our previous measurements on the same cell in the sample environment kit optimised for this purpose.