boiling in water for an appropriate time so as to ensure that any matter other than bone, tusks or teeth is removed;
gamma irradiation at a dose of at least 20 kGy at room temperature (20°C or higher);
soaking, with agitation, in a 4% (w/v) solution of washing soda (sodium carbonate – Na2CO3) maintained at pH 11.5 or above for at least 48 hours;