Quartz spring

Cook (Ref 1), in describing thermal decomposition of some HE s conducted in the quartz spring apparatus (described in Ref 1, p 175 and shown there in Figs 8.1a 8.1b), stated that PETN, RDX, Tetryl and to a small extent TNT decomposed autocatalyti-cally. EDNA followed the first-order decomposition law only until about 5% of the explosive had decomposed and then the reaction stabilized. The term autostabilization was applied here on the supposition that one of the condensed decomposition products of EDNA which accumulated in the explosive apparently tended to stabilize the bulk of expl and thus slow down the decomposition. After about 10% of the expl had decompd, however, the "autocatalysis developed. 

Under isothermal decomposition, he states that it is difficult to maintain isothermal conditions in such strongly exothermic reactions as are involved in the thermal decomposition of explosives owing to their tendency for selfheating. One is also concerned with. the elimination (or minimization) of temperature transients in bringing the sample to the predetermined temp of the experiment. After a brief description of experiments of A.J.B. Robertson and of A.D. Yoffe, conducted in England, the quartz spring apparatus designed by M.A. Cook ... 

M.T. Abegg, IEC 48, 1090(1956), is very briefly described and its schematic diagram is shown in Fig 8.1a, p 175. In this method a small sample of expl, suspended on a thin chain attached to a quartz spring is heated in the furnace shown in Fig 8.1b at a predetermined temperature registered by a thermocouple, and its loss of weight vs time is determined. 

The different properties of water with different bonds to organic molecules can be demonstrated also with dye diffusion measurements in polyamide fibres148,149. Acid dyes show a remarkable decrease of diffusion velocity in 6-polyamide if the humidity content is reduced. It is necessary to heat polyamide fibres in air contact at 150 °C to get similar diffusion velocities of acid dyes at 60 °C under water saturation. The diffusion coefficient of water itself in 6-polyamide depends strongly on the water content148,149 (Fig. 29). This was determined by a quartz spring balance method. 

The weight of gas adsorbed is sometimes measured, and for this purpose various kinds of microbalance have been used. McBain s sorption balance consists of a delicate helical quartz spring,5 suspending the adsorbing solid the upper end of the spring is fixed, and the lower end observed with a cathetometer. Bradley6 has used a balance with a beam, supported in the centre by a fine horizontal quartz fibre and references to other types of balance are given by McBain.7... 

Following crystallization, the solid was separated from the mother liquor by filtration, washed with distilled water, and air dried in an oven at 100 C to remove loosely bound water. Samples of the dried powder were sent routinely to the x-ray laboratory. The fact that we could obtain a strip chart recording of the x-ray powder pattern within 30 minutes was an important factor in the pace of our work. Adsorption evaluations were facilitated by use of multiple, quartz spring, McBain-Bakr balances connected in parallel. As many as 16 adsorbent samples could be evaluated simultaneously. 

Weight loss determinations associated with the loss of bound water were obtained in the course of gravimetric adsorption studies of various vapors on these surfaces. Quartz springs of 250-mg. capacity and sensitivities near 1 mg. per mm. were used in the above system. Outgassing in the 300° to 400° C. temperature range required 4 to 9 days to obtain the required low pressure measurement. 

Adsorption measurements were carried out by a static technique in a gravimetric vacuum apparatus using quartz springs (McBain balances). Benzene and carbon dioxide at 25°C were used as adsorptives. For the determination of the enthalpies of immersion following organic liquids were applied dichloromethane, benzene, cyclohexane and 1,5,9-cyclododecatriene. 

The small-port characteristics of the mordenites were determined by benzene sorption capacities, which were negligible, at low partial pressures of benzene (0.01-0.06) at room temperature using a quartz spring balance. 

Cumene adsorption experiments were carried out in a microbalance apparatus equipped with a quartz spring whose deflections were measured with a cathetometer. The unit also included a vacuum system capable of reducing the pressures to below 0.01 micron, and a Baratron continuous pressure-sensing device with a sensitivity of 1 micron. The amount adsorbed was measured by spring deflection, and checked by material balance on the gas phase based on an approximate chamber volume of 600 cc. The pressure measurements were noted at regular intervals until equilibrium was reached (less than 1 micron change in 5 minutes). These pressure vs. time data were used for diffusivity calculations. 

Patrikeev, Balandin, Klabunovskii and coworkers used siliea gel formed in the presenee of eolonies of the soil bacteria. Bacillus mycoides, that revealed "right" and "left" spiral forms. These "ehiral" siliea forms relate differently towards the optieal isomers of some poisons, for example, (+)- and (-)-aeriehine. On siliea formed in the presence of "right" and "left" forms of Bacillus mycoides the adsorption of (+)- and (-)-linalool was measured in vaeuum on MaeBain quartz spring balance. Silica formed in the presenee of the "left" Bacillus mycoides colony adsorbed 8 times more (-)-linalool than (+)-linalool... 

Qi] Quartz spring thermal balance, SEM, EDAX, EPMA, XRD Sulphidation of Fe-25Cr-4Ti in H2-H2S mixtures at 800°C... 

Figure 4.4.7a. Isopiestic vapor-sorption apparatus using a quartz spring 1 - connection to the vacuum line, 2 - connection to the thermostating unit which realizes the constant measuring temperature T2 (the correct value of T2 is obtained by a Pt-100 resistance thermometer within the cell that is not shown), 3 - closing plug, 4 - quartz spring (reading of its extension is made by a cathetometer), 5 - sample pan with the polymer solution, 6 -pure solvent reservoir at temperature T[. [Reprinted with permission from Ref 82, Copyright 1982, Wiley-VCH].

Figure 4.4.7b. Dynamic isopiesl-ic vapor-sorption apparatus using a quartz spring (drawing provided by G. Sadowski) a) evaporator, b) superheater, c) measuring cell, d) condenser, e) quartz spring, f) polymer sam-ple/solution, g) Pt-100 resistance thermometer. [Reprinted with permission from Ref. 87, Copyright 1995, Wiley-VCH].

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