Cold extraction

A number of different open pond snow and ice storage techniques have been suggested. In Ottawa a storage for 90,000 m3 of snow in an abandoned rock quarry (120 x 80 x 9.5 m3, L x W x H), was studied. The mean cooling load was 7,000 kW. A light colored PE plastic tarpaulin was suggested as insulation, with melt water re-circulation for cold extraction. The estimated payback time was 10 years (Morofsky, 1981). 

The cold extraction method [15] involves moistening defined amounts of pigment powder (between 2 and 20 g) with small amounts of water, alcohol, or a suitable wetting agent. 200 ml of freshly distilled or completely deionized water are then added and the sample allowed to remain in this solvent for 1 h at ambient temperature. After thorough shaking, the liquid is removed by filtration. 

DIN 53 197 Bestimmung des Gehaltes an wasserloslichen Anteilen. ISO 787-8-1983 General methods of test for pigments and extenders, Part 8 Determination of matter soluble in water - cold extraction method. 

Aqueous Extracts. The content of matter soluble in water in pigments is determined by hot or cold extraction of the pigments under prescribed testing conditions. For standards, see Table 1 ( Matter soluble in water ). The decision whether to use hot or cold extraction depends on the properties of the pigment and should be agreed between the interested parties unless otherwise prescribed. 

Some flawless analytical methods do exist but more are needed. Quantitative extraction of all the phenolic compounds from skins and seeds is not possible however we have developed a standard, reproducible procedure. Using a solvent with physicochemical properties similar to wine, one performs three cold extractions followed by two warm ones. This gives an estimate of the total phenols and an idea of their solubilities—an important technological factor. Our work, done in 1969-1972 involved the two principal red varieties of Bordeaux (Merlot and Cabemet-Sauvignon) from two vineyards. One ( ) is a Grand Cru of the Medoc region characterized by fast maturation, and the other (SC) matures more slowly (46, 47). 

The carrageen cold extract contains higher quantities of apparent ketose than does the hot extract from the same source the reverse occurs with C. ocellatus (Table III). 

The pentose content in carrageen was estimated as 1-1.4% (cold extract)68 82 and 1-1.9% (hot extract)68-82 methylpentose was found only in the hot extract82 and to the extent of about half that of the pentose content. 

The ash constituents of the hot and cold extracts from C. crispusM and C. ocellatus80 are shown in Table II. From the table it will be noted that with carrageen the ash of the cold extract consists mainly of potassium and sodium whereas that of the hot extract is composed chiefly of calcium. In the two extracts from C. ocellatus there is not so great a divergence in these respects. It is believed that some requisite amount of the bivalent calcium ion is required for gel formation. 

Treated papers should maintain at a pH in the range 7 and 8.5. The pH should not be higher than 8.5 to prevent alkaline hydrolysis of cellulose. The acidity or alkalinity may be determined as the amount of water-soluble acidity or as the hydrogen ion concentration (pH) of the paper extract. The pH is more indicative of the stability of paper than is the total acidity. The pH can be determined by either a hot or cold extraction method. In the cold extraction method,... 

The fiber residue in the storage bag was tested as pH 4.4 with an Orion Research Ionanalyzer Model 407A using cold extraction techniques. No color from the dyes was evident in the water, but the water became quite yellow. 

Condition The tapa is in extremely fragile and brittle condition. It cannot be unfolded without potentially causing further deunage. There are cracks in the fold lines evident, as well as ragged edges. Cold extraction yielded a pH of 5.7... 

A disassociated fragment was tested as pH 5.7 with an Orion Research Ionanalyzer Model 407A using cold extraction techniques. 

The initial acidity or alkalinity of paper is measured conventionally by the pH of the water extract or by the total titratable acidity or alkalinity of the water extract (TAPPI T428 and ASTM D548). The extract for measurement of pH may be prepared as the cold water extract (TAPPI T509) or as the hot water extract (TAPPI T435 and ASTM D778). In the absence of hydrolyzable salts, it may be expected that hot and cold extraction methods will give approximately the same results. If hydrolyzable acid salts (particularly alum) are present, the hot extraction method yields a lower pH because of hydrolysis promoted at the higher temperature to yield free acids. 

The same approach was soon thereafter applied, at the request of the American Library Association, to library catalog cards. The new nonacid cards made from chemical wood pulps were able to outlast the acidic ones made previously from rag, in spite of rag s potential for higher initial strength. Barrow s proposed specifications for a minimum cold extraction pH of 6.0 and a minimum diagonal folding endurance of 800 are now incorporated in the American National Standards Z 85.1 (4). 

It is not difficult to guess why the time-ratios in Figure 3 increase as degradation proceeds. The cold extraction pH of the acidic paper was found to decrease during the degradation process, reaching pH 3.8 by the end of the experiment. The pH of the buffered paper remained constant. Therefore, it seems probable that the increased value of the time-ratio as degradation occurred is a manifestation of an autocatalytic process. Similar results were obtained in the comparison of samples of a buffered and a not-buffered rag paper. Thus, the autocatalysis process... 

Although pH is a convenient measure of acidity in paper, it is not the same as the concentration of acid in the paper. In a heterogenous material such as paper, the molar concentration of hydrogen ions is not an easily defined quantity (12). Nevertheless, since the buffer system [maleic acid/Ca(OH)2] in the paper is the primary factor controlling the acid content of the paper, one might expect the cold extraction pH to reflect an effective acid concentration. This effective acid concentration can be expressed as shown in Equation 5. Values of [H+] were calculated from... 

Figure 4. Relative rate of (O) tensile strength change and (X) yellowing vs. cold extraction pH for rag paper degradation at 90°C, 100% RH, in...

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