Civil Code (Cap. 16), article 693

693. Any testamentary dispositi on whereby even a sum of money or any other determinate thing is bequeathed to a person designated in the will for the purpose of making such use thereof as the testator shall have declared to have confided to such perso n, shall be null, even though such person shall offer to prove tha t such disposition is in favour of pe rsons capable of receiving proper ty by will, or for lawful purposes. Erroneous designation of heir, legatee or thing disposed of.