Double diffusion method of treating wooden cooling towers comprising treatment with heavy metal sulfate and a water soluble chromate

Claim 1

IN A METHOD OF TREATING THE WOODEN STRUCTURE OF COOLING TOWERS BY IMPREGNATION WITH A WOOD PRESERVATIVE SUBSEQUENT TO FABRICATION THEREOF AND AFTER THE WOODEN STRUCTURE HAS BECOME COMPLETELY SATURATED WITH WATER, THE IMPROVED STEPS OF APPLYING A FIRST SOLUTION CONTAINING A HIGH CONCENTRATION OF A METALLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF COPPER SULFATE AND ZINC SULFATE, TO SAID WOODEN STRUCTURE OF THE TOWER, MAINTAINING SAID FIRST SOLUTION IN CONTACT WITH SAID WOODEN STRUCTURE UNTIL THE LATTER IS IMPREGNATED WITH A CALCULATED AMOUNT OF SAID COMPOUND PER UNIT VOLUME OF THE STRUCTURE, THEN APPLYING A SECOND SOLUTION CONTAINING A WATER SOLUBLE CHROMATE COMPOUND, TO SAID STRUCTURE, THE QUANTITY OF CHROMATE IN SAID SECOND SOLUTION BEING IN EXCESS OF THE STOICHIOMETRIC AMOUNT REQUIRED TO EFFECT PRECIPITATION OF A WATER INSOLUBLE CHROMATE IN SAID WOODEN STRUCTURE, MAINTAINING SAID SECOND SOLUTION IN CONTACT WITH SAID WOODEN STRUCTURE UNTIL SUBSTANTIALLY ALL OF THE METALLIC COMPOUND WITHIN THE WOODEN STRUCTURE FROM SAID FIRST SOLUTION HAS REACTED WITH SAID WATER SOLUBLE CHROMATE TO FORM SAID WATER INSOLUBLE CHROMATE WITHIN THE WOOD, NEXT APPLYING A THIRD SOLUTION CONTAINING ZINC SULFATE TO SAID WOODEN STRUCTURE, AND MAINTAINING SAID THIRD SOLUTION IN CONTACT WITH SAID WOODEN STRUCTURE UNTIL ALL OF THE EXCESS, UNREACTED WATER SOLUBLE CHROMATE IN AND ON THE WOODEN STRUCTURE HAS REACTED WITH SAID ZINC SULFATE.