A Direct Turbidimetric Method for Determining Ethereal Sulfates in Urine”

During the course of an investigation into the excretion of “detoxication products” in the chicken (1) the need arose for a reasonably simple and reliable method for the estimation of “ethereal sulfate” in quantities of 0.1 to 1 mg. of SOa in volumes of some ml. of chicken urine. As none of the methods tried seemed satisfactory in the form described, a modification was developed. It appears that in all methods hitherto described ethereal sulfate is determined as the difference between the free and total sulfate. If the procedure used for the sulfate determination is not very accurate (which is undoubtedly the case with all existing methods when the amount determined is less than 1 mg.), the error inherent in the value for ethereal sulfate may well be considerable. This is also evident from an inspection of the values given in the literature, for instance by Morgulis and Hemphill (2) and Treon and Crutchfield (3). A direct method seems to be preferable. It has been found that free sulfate (together with interfering substances) may be precipitated with barium chloride, and the resulting excess barium by the use of sodium carbonate, without apparent loss of ethereal sulfate. For the determination of sulfate after hydrolysis the turbidimetric method is undoubtedly the most rapid (3), and its accuracy seems quite satisfactory and at any rate not inferior to the benzidine or chromate method. Treon and Crutchfield (3) pointed out that the barium chloride should be added as a solid, not in solution. The stability and reproducibility of the cloud are then very satisfactory. These authors followed the customary practice of using a relatively large quantity of hydrochloric acid for the hydrolysis and subsequently nearly neutralized the acidity of the solution. It is, however, possible to hydrolyze the ethereal sulfates at a relatively low acidity and develop the cloud without neutralization. ReagenkAcid barium chloride solution. Dissolve 1 gm. of barium chloride + 2HzO in water, add 2 ml. of concentrated hydrochloric acid (sp. gr. 1.19), and dilute to 100 ml.