An anti-emetic preparation is made by treating a sparingly-soluble oxalate of a rare earth with a salt of an organic polybasic oxyacid, for example, citric, malic or tartaric acid, to convert it into the colloidal state.  The operation is facilitated by working in an alkaline medium, but is less necessary the higher the basicity of the acid.  Relatively small proportions of the oxyacid salts give colloidal solutions or pastes by grinding in a ball-mill.  With proportions approaching or exceeding the molecular clear solutions are obtained. Protective colloids such as gum arabic may also be employed.  The solutions can be concentrated or dried without destroying their colloidal nature.  According to one example, 5 parts by weight of freshly precipitated oxalates of cerium earth metals (containing all the cerium and yttrium earths from monazite sand) are ground for 48 hours with 1 part water, 0,05--0,06 part sodium citrate, and 0,12 part 20 per cent caustic soda.  In another example, 1 part of the oxalates is heated while stirring with 2 parts of sodium tartrate, 10 of water, and 6 of 10 per cent caustic soda. Other examples describe the preparation of colloidal solutions of cerium, didymium, and lanthanum oxalates.  The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 426,290, and states that the preparations may be made into pills or tablets with the addition of substances improving the taste or facilitating shaping.  An example is given of the preparation of a colloidal solution of thorium oxalate.  This subject-matter does not appear in the Specification as accepted.ALSO:An anti-emetic preparation is made by treating a sparingly-soluble oxalate of a rare earth with a salt of an organic polybasic oxyacid, for example citric, maleic or tartaric acid, to convert it into the colloidal state.  The operation is facilitated by working in an alkaline medium, but this is less necessary the higher the basicity of the acid.  Relatively small proportions of the oxyacid salts give colloidal solutions or pastes by grinding in a ball-mill.  With proportions approaching or exceeding the molecular, clear solutions are obtained. Protective colloids such as gum arabic may also be employed.  The solutions can be concentrated or dried without destroying their colloidal nature.  According to one example, 5 parts by weight of freshly precipitated oxalates of cerium earth metals (containing all the cerium and yttrium earths from monazite sand) are ground for 48 hrs. with 1 part water, 0,05-0,06 part sodium citrate, and 0,12 part 20 per cent caustic soda.  In another example, 1 part of the oxalates is heated while stirring with 2 parts of sodium tartrate, 10 of water, and 6 of 10 per cent caustic soda. Other examples describe the preparation of colloidal solutions of cerium, didymium, and lanthanum oxalates.  The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 426,290, and states that the preparations may be made into pills or tablets with the addition of substances improving the taste or facilitating shaping.  An example is given of the preparation of a colloidal solution of thorium oxalate.  This subject-matter does not appear in the Specification as accepted.