Paper aging procedures

Copper(I) pyrazolate complex 8 was reported to show two phosphorescent properties depending on the cooling procedures to an ordered columnar phase from an isotropic phase by Aida and coworkers (Fig. 10) [34]. Compound 8 shows yellow phosphorescence after slow cooling with deliberate aging. On the other hand, red phosphorescence is observed by rapid cooling. A rewritable phosphorescent paper was prepared by using compound 8. 

Even today, in an age where analytical quality assurance procedures and accreditation are part of most laboratories daily routines, an often-neglected section in a published paper is where you describe the quality control procedures you have used during the analytical work. It is only natural that the author points out what he/she thinks has been done well. It is equally natural that the weak spots have been suppressed or otherwise disregarded. What procedures the author will describe are thus rather subjective. 

The molecular weight distribution of rag papers from four centuries is shown in Fig. 17. The highest Mw in this example was observed for the oldest paper. Endurance and stability of rag paper is highly influenced by the provenience of the material, the papermaking procedure and the storage conditions. Thus, no conclusion as to the age can be drawn from the molecular weight distributions measured. 

The determination of a complete Arrhenius relation is a long procedure. Even for quite unstable materials, degradation rates are low as room temperatures are approached, yet room temperature must be approached to minimize the errors of extrapolation. Once the slope of the line is established for a given material, the regression data from one oven-aging experiment can be translated to life at room temperature for other samples. Unfortunately, much of the Arrhenius data at hand for paper does not separate hydrolytic from oxidative degradation. The method will make more reliable predictions when such a separation is made. 

Papers which are acidic as manufactured can be stabilized by a deacidification procedure. Several processes have been developed for this purpose, the most successful of which provide neutralization of the acid present and leave a residue such as calcium carbonate or magnesium carbonate as reserve alkalinity in the paper. This alkalinity serves to protect the paper as acidity develops from paper components during aging or is introduced by atmospheric contamination. The amount of reserve alkalinity can be determined by adding a measured volume of standard acid solution in excess to a weighed specimen of the paper and back-titrating the excess to neutrality with standard base solution. 

Several investigators have studied the effects of deacidification on paper. Flieder (7) evaluated several deacidification procedures using breaking length, fold, burst, tear, reflectance, opacity, pH, copper number, and ash as criteria of change. Accelerated aging for 72 h at 105 °C and for 4 h at 87°C and 60% relative humidity was employed as measures... 

In reviewing the literature on the effect of deacidification on paper, three important factors emerge (a) it is desirable to work with papers that are reproducible, well characterized, and similar in properties, both chemical and physical, to old papers (b) much more work needs to be done on the interaction of metals with the carboxyls in cellulose and (c) a standard procedure for accelerated aging that includes some moisture in the aging atmosphere is desperately needed. 

This procedure was applied also to BP, UBP, and GP samples that had been thermally aged at 90 °C and 50 rh for 20 days prior to extraction. The transmit-tances of 5 solutions of the neutral extracts at 460 nm, obtained with a Bausch and Lomb Spectronic 20 spectrophotometer, are noted in Table II. Whatman No. 42 filter paper was used as the substrate for the extracted material. When the sheets were dipped in the 60-mL concentrate, the pickup was found to be about 15. ... 

Filter Paper with Hemicellulosic Fractions Added On. Hemicellu-lose fractions were isolated from unaged and thermally aged papers by extraction with LiOH, following the procedure described by Giertz and McPherson (6). The changes in postcolor number [100(K/S) — (K/S)0] (7) for various test sheets during exposure to visible and UV radiation and to heat are shown in Figures la, lb, and lc for material extracted from... 

The original report32 of the titanium-catalyzed asymmetric epoxidation of allylic alcohols in 1980 has been followed by hundreds of applications, the majority of which use the initially reported conditions. In the decade since the introduction of this reaction numerous improvements have been made41. The most complete discussion of the preparative aspects of both the asymmetric epoxidation and the kinetic resolution was presented by the Sharpless group42. This paper details the effects of reagent stoichiometry and concentration, substrate concentration, aging of the catalyst and variation of oxidant, solvent and tartrate as well as workup procedures. What is particularly noteworthy in this presentation is that significant amounts of unpublished work are drawn upon to develop recommendations for successful reaction. 

Alkaline degradation is possible but occurs much less readily than acid degradation. Degradation in alkaline conditions is of interest to the paper scientist mostly because of the degradation which may occur during analytical procedures rather than what may happen during the ageing of paper. 

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