Process of refining hardwood pulp

Claim 1

THE PROCESS OF REFINING PRELIBERATED HARDWOOD PULP TO ETHER-SOLUBLE CONTENTS LESS THAN 0.10% IN A MULTISTAGE CHEMICAL REFINING PROCESS, INCLUDING A HOT CAUSTIC-SOAP STAGE, COMPRISING SUBJECTING THE HARDWOOD PULP, IN THE HOT CAUSTICSOAP STAGE, TO HOT CAUSTIC SODA REFINING LIQUOR HAVING A SOAP CONCENTRATION BETWEEN ABOUT 0.11% AND 0.56% BASED ON THE SOLUTION, AND REGULATING THE INITIAL STOCK CONSISTENCY IN SAID STAGE BETWEEN ABOUT 6.25% AND ABOUT 25% AND THE CONCENTRATION OF CAUSTIC SODA IN THE REFINING LIQUOR IN SAID STAGE BETWEEN ABOUT 1.54% AND 6.66% BASED ON THE SOLUTION, SO THAT IN A GRAPH PLOTTING THE PER CENT INITIAL STOCK CONSISTENCY AGAINST THE PER CENT INITIAL CAUSTIC SODA BASED ON THE SOLUTION, THE PER CENT OF CAUSTIC SODA BASED ON THE SOLUTION LIES ABOVE A STRAIGHT LINE EXTENDING THROUGH THE PLOTS FOR ABOUT 1.54% CAUSTIC SODA CONCENTRATION AT 6.25% STOCK CONSISTENCY AND 2.7% CAUSTIC SODA CONCENTRATION AT 25% STOCK CONSISTENCY.