DURING the course of work on mineral levels in chick feeds, certain observations have been made on the method for the determination of the effectiveness of vitamin D supplements by means of bone ash, which should be considered in selecting a uniform standard method for this analytical procedure. A survey of the methods used shows that numerous variations of the general method are used. Bones are preserved in alcohol or in formaldehyde, or are dried. The temperature of drying varies from 60° to 115° C. Vacuum drying is also used. Some workers remove the cartilage cap from the bone, or from one end of the bone; others do not. There is variation in practice regarding the crushing or grinding of the bone. Some workers use alcohol to extract the fat, others use ether, while a combination of the two is used by some investigators. The time of extraction varies from . . .
