Alkaline reserve

Benzoate can be used as an anodic inhibitor and is effective at preventing waterline attack. Phosphate is also sometimes included. Sodium borate (borax) is usually added to the formulation to provide an alkalinity reserve buffer. Typically, a copper inhibitor such as benzo-triazole (BTA) or tolyltriazole (TTA) also forms part of a formulation and is used to provide yellow metal (copper and brasses) protection. 

Borate is usually added to nitrite-based formulations to provide an alkalinity reserve buffer, ensuring that the system water pH level is maintained within the range of 7.5 to 9.5 (or greater). 

As boiler pressures increase, FW quality also tends to improve and is more than likely to be almost fully deaerated at higher pressure. Consequently, tannin reserves and residuals may be reduced accordingly. Also, because there is likely to be lower alkalinity reserves at higher boiler pressures, the tannin reserve must be lowered if insol-... 

NOTE Sufficient caustic is still required to maintain a suitable OH alkalinity reserve. Tests to confirm the presence of adequate alkalinity and a permanent phosphate reserve should be conducted frequently, normally at least once per day. 

Where chelants or all-polymer/all-organics are employed in FT boilers the control limits shown for boilers up to 350 psig/25 bar are applicable as a starting point, although slightly higher conductivity levels and OH alkalinity reserves may be possible. 

Transfer 150 ml of the silver nitrate reagent to each of two 250-ml glass-stoppered Erlenmeyer flasks. Place the flasks in a suitable ice bath until, die temperature of the contents Is 32°to 39.2 F (0° to 4°C). Add 7 to 9 drops of the mixed indicator to each flask and, if necessary, neutralize to a gray-green color with 0.02N sodium hydroxide if. acid or with 0.02N nitric acid if alkaline. Reserve one of the flasks for the blank and into the second flask pour 0 ml of propellant. Compare the color of the sample with that of the blank. A purple color in the sample solution indicates... 

Typically, acid is used to destroy almost all of the makeup water alkalinity, with recirculating water alkalinity reserves of some cooling systems being cut down to only 30 to 60 ppm, or a pH of 7.2 to 7.4. 

The effect of the presence of water in oil in terms of alkaline reserve of oil, pH (extract) and TBN value was investigated (Fox et al., 1990 Pawlak et al., 1985). The soluble acid/base content has been determined by extraction into either DI water, 7% synthetic sea water solution or aqueous ethanol mixture (1 1, v/v). Extraction of oil samples by aqueous ethanol mixture (1 1, v/v) was applied to new and used samples of an SAE 30 oil. The relationship between pH extracted in aqueous ethanol and TBN value is shown in curve I, Fig. 6.8. 

Magnesium methoxide has been found to be a very effective neutralizer. However, on a damp day or with a damp paper, the solution tends to precipitate prematurely and leave surface deposits on the treated paper. Methyl magnesium carbonate is also effective but much less sensitive to water. Both these products produce adequate alkaline reserves in paper. Since methanol is used as the solvent, the deacidification should be conducted in a well-ventilated hood. 

Zinc oxide deposited in paper provides an "alkaline reserve (which is more nearly neutral in pH than the more commonly used calcium and magnesium reserves) by reacting with any strong or weak acids introduced into the paper subsequent to the deacidification process ... 

The amount of zinc oxide in the treated paper, and hence the alkaline reserve, can be controlled by the amount of moisture in the paper at the time of treatment sufficient DEZ is added to react with all the acid and water present. 

After the books are removed from the processing chamber, during the overnight recovery, or subsequently in the library, the magnesium hydroxide and magnesium carbonate can release moisture or carbon dioxide to the ambient air to form the basic magnesium carbonate [MgO MgC03 Mg(0H2)] and function as the alkaline reserve. 

Should uniformly neutralize and uniformly deposit alkaline reserve. The alkaline reserve should be two to three percent in concentration for maximum permanence. 

DEZ Process. DEZ process has been developed and refined by chemists at the Library of Congress since 1974. It is a very impressive method of deacidifying book papers effectively and uniformly. There is no doubt that the deacidification chemistry is workable. As shown in Table I, the DEZ process is the process that met most of the "ideal" criteria. In essence, the DEZ process uniformly and consistently neutralizes all excess acid in the paper, leaves a uniformly distributed alkaline reserve in all regions of the book page and the paper fiber. 

The reaction of diethyl zinc with water produces zinc oxide, and then zinc carbonate, as the alkaline reserve. These chemicals have antiseptic properties which may also prevent the growth of mold in paper. They may also improve the brightness of treated papers. However, it is also known that zine oxide is a photosensitizer (56) which may trigger photo-oxidation of treated papers to initiate a chemical chain reaction that will lead eventually to the formation of acidic products (57). Moreover, the interaction of zinc oxide and zinc carbonate with copper, iron and cobalt present in the paper and their subsequent effects on paper stability have not been studied. 

Koppers "Book Keeping" Process. In view of the limitation of the Wei T o process, chemists at the Koppers Company developed a "Book Keeper" process by dispersing submicron particles of basic metal oxides, hydroxides or salts of calcium, magnesium, or zinc, in a suitable gas such as Freon or liquid medium, so that the active chemicals can be transferred and deposited electrostatically on the surface of paper. It also does not require pre-drying of books as is required for both the DEZ and Wei T o processes. The testing results appear satisfactory as shown in Table I. The major concern with this process is the distribution of the alkaline reserve on the paper. It appears the process deposits alkaline chemicals on the surface of paper and achieves surface deacidification. However, acid formed in the core of the paper is not neutralized. Koppers intends to prove the degrees of chemical penetration and neutralization of acid in the center layers by examination of the cross-section of paper by SEM. 

Langwell Vapor Phase Deacidification Process. Langwell s VPD process is a very simple process. Cyclohexylamine carbonate is inserted between book pages to achieve partial deacidification. However, this process does not create an alkaline reserve in treated products to prevent future acid attack. Cyclohexylamine carbonate will react with some plastic covers, inks and colors. Preselection of books is required. The odor and the carcinogenic nature of the vapor are also critical factors that limit the use of VPD process as a mass deacidification process (46-54). 

Aqueous Extract pH. The purpose of a deacidification treatment is to neutralize internally-generated carboxyl groups as well as acids from dyeing, finishing or exposure to the environment. Ideally an alkaline reserve should be deposited in the fibers to combat future acidity. Fabrics... 

Figures 4 and 4A and Table IV show the results when the paper was neutralized by immersion in 0.1% sodium carbonate. The aging results are now surprisingly good, almost equal to those obtained with magnesium as given in Figure 2 and Table I. The paper, however, does not have an alkaline reserve and will not be stable in an acid atmosphere. Furthermore, as the next experiment shows, an alkaline reserve cannot be established using sodium carbonate.

Temperature and humid conditions of storage, and the presence of oxidation catalysts in the paper, as well as the pH and alkaline reserve, must be taken into account in applying the Arrhenius relation to predict the life of paper. 

One of the most widely used nonaqueous deacidification processes is that proposed by Smith (7) based on a methanol or methanol-Freon solution of magnesium methoxide. This process is very effective and leaves a good alkaline reserve, but the magnesium methoxide is very sensitive to water, and this leads to inconvenience in the handling and processing of paper as a result of premature precipitation. These inconveniences were recognized, and a better nonaqueous deacidification agent... 

Resistance to Polluted Atmospheres. There is general agreement that it is desirable for a deacidified paper to have built into it some degree of protection against future inadvertent exposures to acidic atmospheres. The buffering capacity of a paper above pH 7.0 is termed "alkaline reserve. There is no consensus as to the necessary extent of this reserve, but the Preservation Office of the Library of Congress has suggested 3% as a reasonable level for reserve alkalinity, expressed as calcium carbonate. 

A much more recent development is the morpholine process in which fifty books per hour are treated in an evacuated chamber with morpholine-water vapor (12). In its present form, it was effective on 95% of the papers treated, prolonging their life on average by a factor of 4-5 (Figure 7). Though it does not leave a titratable alkaline reserve in the paper, acid papers treated in this manner aged in the presence of 5 ppm S02 at 75 °C and 60% relative humidity deteriorate more slowly than if untreated. Recent tests of twenty treated books at the Library of Congress show that their pH has not declined in two years. The equipment for the process was set up in the Virginia State Library where 35,000 books were treated in the first seven months of operation. 

Use of a chemical feeder allows the conservator to wash paper with deionized water containing added calcium ions, wash and deacidify simultaneously, or to directly deacidify paper. Examples of these processes are given in which varying ratios of alkali were fed to deionized water. The resultant alkaline reserves produced in two types of papers are shown. 

Acidity and Alkaline Reserve Measurements. Acidity was titrated directly with standard NaOH solution to determine total acid content. 

Alkaline reserve was measured by acidifying to pH 3, boiling to remove C02, cooling, and back titration with standard NaOH solution to pH 7 (4). 

Alkaline Reserve. The alkaline reserve served to protect paper from acidity, either from a polluted environment or from the paper structure itself. It is very important that the treatment leave an adequate... 

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