Abstract: In this paper a new method for determination of the concentrarion of phosphorus and phosphide in solid and liquid State has ho built.The solid or liquid samples containing phosphorus to be measured react with atomic hydrogen Which is obtained by decomposition of KBH₄.The product PH₃ is then determined by gas chromatography.This method does not require any preeret and is fast,sensitive and reliable,and the result is practically the same as spectrophotometric method.