Quartz reaction with water

Hazard Extremely reactive. Destroys glass instantly, attacks quartz readily in presence of moisture. Organic matter bursts into flame on contact. Violent reaction with water. Extremely corrosive to skin, eyes, mucous membranes, and respiratory tissues. 

Formula weight 92.46. Golorless gas, suffocating odor strongly attacks the bronchi. Extremely reactive, particularly as a liquid. Immediately destroys glass and, in presence of traces of moisture, quartz. Organic substances usually react with ignition. The reaction with water is explosive. 

Very reactive reacts with nearly all elements with ignition. Vigorous, nearly explosive reaction with water. At room temperature, dry glass is attacked slowly, quartz glass practically not at all. Mercury becomes coated with a brown film. 

The second analytical method uses a combustion system (O Neil et al. 1994) in place of reaction with BrF,. This method was used for the crocodiles because they were represented by very thin caps of enamel. The enamel was powdered and sieved (20 mg), pretreated in NaOCl to oxidize organic material and then precipitated as silver phosphate. Approximately 10-20 mg of silver phosphate were mixed with powdered graphite in quartz tubes, evacuated and sealed. Combustion at 1,200°C was followed by rapid cooling in water which prevents isotopic fractionation between the CO2 produced and the residual solid in the tube. Analyses of separate aliquots from the same sample typically showed precisions of 0.1%o to 0.4%o with 2 to 4 repetitive analyses even though yields are on the order of 25%. 

The catalyst for the in situ FTIR-transmission measurements was pressed into a self-supporting wafer (diameter 3 cm, weight 10 mg). The wafer was placed at the center of the quartz-made IR cell which was equipped with two NaCl windows. The NaCI window s were cooled with water flow, thus the catalyst could be heated to 1000 K in the cell. A thermocouple was set close to the sample wafer to detect the temperature of the catalyst. The cell was connected to a closed-gas-circulation system which was linked to a vacuum line. The gases used for adsorption and reaction experiments were O, (99.95%), 0, (isotope purity, 97.5%), H2 (99.999%), CH4 (99.99%) and CD4 (isotope purity, 99.9%). For the reaction, the gases were circulated by a circulation pump and the products w ere removed by using an appropriate cold trap (e.g. dry-ice ethanol trap). The IR measurements were carried out with a JASCO FT/IR-7000 sprectrometer. Most of the spectra were recorded w ith 4 cm resolution and 50 scans. 

Mortars of this system are prepared by blending ignited magnesium oxide, ADP and STPP with a filler, normally quartz sand. On mixing with water a cementitious mass is formed. The reaction has been studied by a number of workers Kato et al. (1976), Takeda et al. (1979), Neiman ... 

Abdelrazig, Sharp El-Jazairi (1988, 1989) prepared a series of mortars based on a powder blend of MgO and ADP with a quartz sand filler. They were hydrated by mixing with water. A mortar I (MgO ADP silica water = 17T 12-9 70-0 12-5), with a water/solid ratio of 1 8, formed a workable paste which set in 7 minutes with evolution of ammonia. The main hydration product, struvite, was formed in appreciable amounts within 5 minutes and continued to increase. Schertelite also appeared, but only in minor amounts, within the first 5 minutes and persisted only during the first hour of the reaction. Dittmarite appeared in minor amounts after 15 minutes, and persisted. 

Fig. 16.1. Results of reacting quartz sand at 100°C with deionized water, calculated according to a kinetic rate law. Top diagram shows how the saturation state Q/K of quartz varies with time bottom plot shows change in amount (mmol) of quartz in system (bold line). The slope of the tangent to the curve (fine line) is the instantaneous reaction rate, the negative of the dissolution rate, shown at one day of reaction.

Fig. 26.1. Reaction of quartz with water at 25 °C, showing approach to equilibrium (dashed lines) with time. Top diagram shows variation in SiC>2(aq) concentration and bottom plot shows change in quartz saturation. In calculation A, the fluid is initially undersaturated with respect to quartz in B it is supersaturated.

Fig. 26.2. Kinetic reaction of quartz and cristobalite with water at 25 °C. In calculation A the fluid is originally in equilibrium with quartz, in B with cristobalite. The top diagram shows how the SiChlaq) concentration varies with time, and the bottom plot shows the change in quartz saturation. The reaction paths approach a steady state in which the fluid...

Preparative Photolysis. The preparative photolysis of an aqueous solution (pH=8.5) of AETSAPPE (2.5 M) was conducted in a 1-inch diameter quartz test tube in a Rayonet Reactor (Southern New England Radiation Co.) fitted with 254 nm lamps. Within two hours the solution gelled and the reaction was terminated. Upon acidification the solution cleared, and the product could be re-precipitated by addition of base. This indicates loss of the thiosulfate functionality. The product was dissolved in dilute HC1, precipitated with acetone, and filtered. This process was repeated three times, and the final precipitate was washed with water. The product (20 to 30 mg) was dried in vacuo for 24 hours and stored in a dessicator until use. Comparison of the13 C NMR spectrum of the product with the starting AETSAPPE 13C NMR spectrum clearly shows that the thiosulfate methylene peak shifted upfield, from 39 ppm to 35 ppm. The complete 13 C NMR and IR analysis of the product were consistent with the disulfide product. Further, elemental analysis of the product confirmed that the product was the desired disulfide product 2-amino (2-hydroxy 3-(phenyl ether) propyl) ethyl disulfide (AHPEPED) Expected C 58.39, H 7.08, N 6.20, S 14.18 actual C 58.26, H 7.22, N 6.06, S 14.28. 

The reaction apparatus (Figure 1) requires a tubular quartz flask with two side arms and a large ground-glass joint at the top to accommodate the water-cooled UV lamp. 

Oxides/Oxyhydroxides. For natural solids that are oxides or oxyhydroxides (e.g., quartz, Si02 goethite, a-FeOOH gibbsite, Al(OH)3), their water-wet surface is covered by hydroxyl groups (recall Fig. 11.2). These hydroxyl moieties can undergo proton-exchange reactions with the aqueous solution much like dissolved acids ... 

Application of the Jkagmts,—Having thus described the properties and characteristic reactions of the different metals which it is desirable to look for as being frequently associated with gold, lot it now be assumed that the substance to be examined is a piece of. auriferous quartz, TbiB must be first reduced to powder, and then boiled for some time in an earthenware or glass dish with aqua regia. The solution ie then diluted with water, passed through a filter, and allowed to cool. If any silver bo present, it will remain in the filter as a white precipitate, mixed with the quartz. 

Gas-phase heterogeneous reactions have been carried out in a closed circulating system evacuable to high vacuum (Fig. 13.1). For heterogeneous photocatalytic reactions, a quartz reaction cell with flat bottom (R. C. in Fig. 13.1) has been used. When Pt/Ti02 powder is spread over the bottom of the cell followed by evacuation (this is referred to as dry state) and illuminated in the presence of gas-phase water, neither H2 nor 02 is observed. The same is true for... 

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