Abstract
The principles and techniques for the determination of vitamin B_<12> binding power in biological materials are described for the benefit of the reader. This paper which is the first half of the article details the growth inhibition method and the dialysis method. The former consists of the determination of "free"vitamin B_<12> by direct addition of the material to the culture media and calculation of the "bound" from from the total and free vitamin B_<12> activities as measured microbiologically. The factors influencing the result are commented critically. The latter is subdivided into three techniques of "exhaustive", "equilibrium"and "partial"dialyses, and the advantages of the use of radioactive vitamin B_<12>, the source of error, experimental design and calculation are discussed for each technique.
