Method of measuring the ph of aqueous liquids, moist foodstuffs, and the like

Claim 1

THE PROCESS OF MEASURING THE PH OF AQUEOUS LIQUIDS, MOIST FOODSTUFFS AND LIKE, WHICH COMPRISES HOLDING IN DIRECT CONTACT WITH A MOIST MAERIAL WHOSE PH IS TO BE MEASURED A THIN BODY OF TRANSPARENT, SEMI-PERMEABLE, HYDROPHILLIC, WATERINSOLUBLE COLLOIDAL PLASTIC HAVING UNIFORMLY INCORPORATED IN THE BODY THEREOF A PH INDICATOR DYE IN A CONCENTRATION WITHIN THE RANGE OF FROM ABOUT 0.0005 TO 20 PER CENT BY WEIGHT; SAID DYE CHANGING COLOR DUE TO PH OF THE MATERIAL WHOSE PH PH INCLUDING THE PH OF THE MATERIAL WHOSE PH IS TO BE MEASURED; SAID BODY OF PLASTIC BEING SUFFICIENTLY THIN TO A RESPOND QUICKLY TO CHANGES TO PH WHEN CONTACTED WITH SAID MATERIAL AND SUFFICIENTLY POROUS TO BE PERMEABLE TO HYDROGEN AND HYDROXYL IONS BUT HAVING PORES SUFFICIENTLY SMALL SUBSTANTIALLY TO HINDER DIFFUSION OF THE DYE MOLECULES; AND COMPARING THE COLOR OF SAID PLASTIC BODY WITH PH COLOR STANDARDS AFTER IT HAS BEEN HELD IN CONTACT WITH SAID MATERIAL FOR A TIME SUFFICIENT TO ASSUME A COLOR CORRESPONDING TO THE PH OF SAID MATERIAL.