A Source of Error in the Absorptiometric Determination of Inorganic and Total Phosphorus in Sea Water

Abstract

The results of phosphate determinations in sea water by the Deniges method, using red light, in an absorptiometer, may be in error if the stannous chloride reagent has low HC1 concentration, and contains stannic tin. The error is in the reagent blank determination, and seems to be caused by colloidal stannic compounds which increase the opacity of the solution. In sea water the effect may be smaller or immeasurable so that results are over-corrected. When the stannous chloride solution contains about 5% hydrochloric acid, reagent blank figures are low, and independent of stannic tin concentration. This acidity is recommended.