Glasses acid classes

ETAAS Acid-washed glass PE Class 100 5% HN03) 12 h Yes 0.54-3.51 [95]... 

Glasses. There are three classes of acid dyes acid leveling, acid milling, and super milling. 

In the glass-bottle industry the bottles can be cooled in a dilute SOj/SO, atmosphere to increase chemical resistance. A similar effect has been noted with vitreous enamel. It has been postulated that a thin layer of —OH groups or — OH—HjO (hydronium) ions is adsorbed on the surface of a fired enamel. These ions are transformed into — OSO, or —OSO3 in the presence of oxides of sulphur which are more resistant to further acid attack. It is known that the acid resistance of a recently fired enamel improves on ageing, probably due to the enamel reaction with SOj/SO, in the atmosphere and it is quite common for the grading to improve from Class A to Class AA (BS 1344). 

The two matrices in these cements are of a different nature an ionomer salt hydrogel and polyHEMA. For thermodynamic reasons, they do not interpenetrate but phase-separate as they are formed. In order to prevent phase separation, another version of resin glass polyalkenoate cement has been formulated by Mitra (1989). This is marketed as VitraBond, which we term a class II material. In these materials poly(acrylic acid), PAA, is replaced by modified PAAs. In these modified PAAs a small fraction of the pendant -COOH groups are converted to unsaturated groups by condensation reaction with a methacrylate containing a reactive terminal group. These methacrylates can be represented by the formula ... 

Globular proteins were much more difficult to prepare in an ordered form. In 1934, Bernal and Crowfoot (Hodgkin) found, that crystals were better preserved if they were kept in contact with their mother liquor sealed in thin-walled glass capillaries. By the early 1940s crystal classes and unit cell dimensions had been determined for insulin, horse haemoglobin, RNAase, pepsin, and chymotrypsin. Complete resolution of the structures required identification of the crystal axes and some knowledge of the amino acid sequence of the protein—requirements which could not be met until the 1950s. 

Chemical Properties of Glass.—Among the chemical properties of glass, there are some which merit an attentive examination. Dumas classes them as follows—namely, the effect of tire air or of deoxidizing bodies that of water that of acids and that of bases. - ... 

Action, of Acids.—The acids, in their turn, should act on glasses with facility. Among these, the hydrofluoric acid must be classed by itself, its action being quite peculiar. The other acids tend to decompose glass, by seizing on the bases and setting tho silica free. 

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