The Phthalein Test

Phenolsulphonephthalein, which was first described by Remsen,1 is a bright red crystalline powder, somewhat soluble in water and alcohol and readily soluble in the presence of alkalies.The drug, as determined by Abel and Rowntree,2 is non-toxic, non-irritant locally, and is excreted practically entirely by the kidneys and with extraordinary rapidity, appearing in the urine normally within a few minutes of injection.In alkaline solution it presents a brilliant red color which is ideally adapted for quantitative colorimetric estimation. TECHNICIn our earliest work only the time of appearance, the time of maxi- mum intensity of excretion, and the time of gross elimination were con- sidered.In the course of the work it became evident that the color properties of this substance make it peculiarly well adapted for colori- metric methods of estimation, and for this purpose the Duboscq colori- meter was employed and has proved of the greatest value.In order to obtain data of real value it is essential to any functional test to know, not only the time of appearance of the drug in the urine, but exactly what part of the drug, a known amount of which has been administered, is recovered in a definite period of time.Twenty minutes to half an hour before administering the test, the patient is given 200 to 400 c.c. of water in order to insure free urinary secretion, otherwise delayed time of appearance may be due to lack of secretion.Under aseptic precautions a catheter is introduced into the bladder and the bladder completely emptied.Noting the time, 1 c.c. of a care- fully prepared solution3 of the phenolsulphonephthalein containing 6 mg.