He solubility in silicate glasses at 250 degree C; a model for calculation

Published helium solubility data on silicate glasses of simple composition are used in the present study to calculate to a fair degree of accuracy, the He solubility in glasses of a wide range of compositions. The model proposed here relates the Henry's law solubility constant, S, to the mole fraction of oxide component, Xj, in the glass according to: In S = Sigma X (sub j) ,k (sub j) where k (sub j) is a constant determined from literature data. In the case of unmixed glasses (SiO (sub 2) > or = 75%), the k (sub j) values obtained are, respectively, -12.418, -19.992, -16.029, -12.950, -10.466, -13.671 and -19.964 for SiO (sub 2) , Na (sub 2) O, Li (sub 2) O, CaO, Al (sub 2) O (sub 3) , TiO (sub 2) and K (sub 2) O. In the other cases (SiO (sub 2) < or = 75%), these constants are estimated to be -10.868, -23.960, -27.156, -18.571 and -14.210, respectively, for SiO (sub 2) , Na (sub 2) O, Li (sub 2) O, CaO and Al (sub 2) O (sub 3) . Use of these k (sub j) values together with reasonable assumptions concerning TiO (sub 2) , FeO and MgO enables the calculation of model He solubilities for natural glasses (e.g. a basaltic glass and an obsidian glass). The results compare well with published experimental data.