Vitreous substance

The great sixteenth-century French ceramist Bernard Palissy (86) once wrote I know no plant nor mineral nor any substance which can tinge stones blue or azure except saphre, which is a mineral earth, extracted from gold, silver, and copper, which has very little color, except gray inclining a little toward the violet. Whenever the said saphre is incorporated with vitreous substances, it makes a marvelously fine azure hence one may know that all stones having an azure color have taken their tint from the said saphre (72). 

Cryolite, Na3AlF6, a double fluoride of sodium aluminum. It occurs as a white, sometimes red, brown or black vitreous substance in Greenland, Colorado Russia and as a synthetic made from fluorspar, H2S04, hydrated alumina Na carbonate (Refs 1 6)... 

Cupric metaborate, Cu(BQ2)2.—The metaborate is prepared by fusing cupric nitrate with excess of boric acid.1 It forms blue, doubly refracting crystals, density 3-86, and is also known as a hard, vitreous substance of density 3-6. 

Davlin, A. 0.,Method for adhering precious metal to vitreous substances, U.S. patent 6,231,925,... 

The classification depends upon whether the clay was melted during the firing process into a glassy (vitreous) substance or not. Within these divisions we have the following ... 

In the giant molecule description, one can think of the structure as starting by a crystal characterized by its elementary cell repeated periodically in the three directions of the real space. Then, as the disorder establishes, the size of the elementary cell increases, implying reduction of the associated Brillouin zone in the reciprocal space and so on [11], until one can assimilate the final vitreous substance to a giant molecule that is to a unique cell... 

A vitreous enamel coating is, as the name implies, a coating of a glassy substance which has been fused onto the basis metal to give a tightly adherent hard finish resistant to many abrasive and corrosive materials. The purpose of modern vitreous enamels is twofold, i.e. to confer corrosion protection to the metal substrate and at the same time to provide permanent colour, gloss and other aesthetic values. 

The posterior segment of the eye contains vitreous humor (a clear jelly-like substance), the retina, the retinal vasculature, and the optic nerve head. The retina transforms light energy... 

Figure 5 Changes in volume, V, energy, E, and enthalpy, H, during cooling or heating of the liquid, crystalline, and glassy (vitreous) forms of a substance. Tm is the melting point, and Ts is the glass transition temperature. (Adapted with permission from Ref. 14.)...

Yoshida has studied anodic oxidations in methanol containing cyanide to elucidate the electrode processes themselves.288 He finds that, under controlled potential ( 1.2 V), 2,5-dimethylfuran gives a methoxynitrile as well as a dimethoxy compound (Scheme 57). Cyanide competes for the primary cation radical but not for the secondary cations so that the product always contains at least one methoxy group. On a platinum electrode the cis-trans ratio in the methoxynitrile fraction is affected by the substrate concentration and by the addition of aromatic substances suggesting that adsorption on the electrode helps determine the stereochemistry. On a vitreous carbon electrode, which does not strongly adsorb aromatic species, the ratio always approaches the equilibrium value. 

Biosamples, taken from living people (mainly blood and urine) and from corpses during autopsy (blood, urine, vitreous humor, bile, and almost any tissue and organ), are analyzed for substances that are toxicologically relevant. Alternative matrices like hair and saliva are also considered for determination of illicit chugs. 

Among the methods used, the determination of selected of analytes in vitreous humor (and of potassium in particular, based on the observation that its concentration progressively increases in this substrate after death) has been often adopted in the attempt to reduce imprecision of the estimate. Recently, for example, Munoz et al. [142] have developed an HPLC method for the determination of hypoxanthine, another substance whose concentration has been found to increase after death in vitreous humor. Separation was carried out under RP conditions using a mobile phase of KH2PO4 0.05M (pH 3) containing 1% (v/v) methanol at a flow rate of 1.5mL/min. UV spectra were recorded in the range 200-400 nm. Based on the analysis of samples collected at different PMIs, the authors found that about 53% of the variation in the data is explained by PMI. 

M. Winter, C. Eckardt, B. Havsteen, Vitreous changes after contact with high-density substances an in vitro experiment, Ger. J. Ophthalmol. 1(1992)268A. 

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