Cahn electrobalance

Fig. 11-13. Apparatus for measuring the time dependence of interfacial tension (from Ref. 34). The air and aspirator connections allow for establishing the desired level of ftesh surface. IV denotes the Wilhelmy slide, suspended from a Cahn electrobalance with a recorder output.

A portion (10.2 cm x 17.8 cm) of each RSP sample was sequentially extracted in a Soxhlet apparatus with cyclohexane, di-chloromethane and acetone, (8 hr. for each solvent) in the order given. A more complete extraction of the organic compounds present in particulate matter is achieved and a partial separation of the organic compounds into non-polar, moderately polar and polar fractions is obtained by this method. The volume of each extract was reduced to 10.0 ml using a rotary evaporator. The samples were then stored in a freezer at -15 C until further analysis. Weights of extracts were determined by weighing duplicate 100 yl aliquots of each, taken to dryness on a slide warmer (40 C), on a Cahn Electrobalance. 

Sorption Properties. Sorption isotherms were determined of n-hexane and 2,3-dimethylbutane on variously pretreated samples of zeolite by a gravimetric method using a Cahn electrobalance. No shape-selective sorption was observed for these sorbates, which bespeaks a pore size greater than about 0.5 nm. The sorption capacity of S2 was appreciably lower than that of zeolite X, Y, or mordenite. Routine sorption capacities were determined by a simple procedure of pore filling with benzene at room temperature after calcination of the samples at various temperatures. 

Cahn Electrobalance, Cahn Instrument Co., Downey, California. 

Figure 1. Schematic of the Cahn electrobalance used for measuring coal and...

The overall precision is not limited by the quality of the force measurement. Several sensitive and accurate tensiometers are available, some commercially, the well-known Cahn electrobalance being one of these. The force measurement is based on a few basic principles, like the torsion of a wire or electromagnetic feedback. Of these the former is obsolete nowadays. However, an everyday good, analytical balance is also adequate. 

The Cahn electrobalance is a sensitive, accurate, reliable, and easily operated balance which is based on a D Arsonval galvanometer, with the sample... 

A sample holder which is widely used with Cahn Electrobalance is shown in (a). It is 5-9 mm in diameter and is constructed of platinum or quartz with the geometrical shape of a hemisphere. Sample sizes from 1-20 mg... 

Balances. Balances must remain precise and accurate continuously under extreme temperature and atmospheric conditions, and should deliver a signal suitable for continuous recording. These requirements may be met in many ways the two books by Duval and Wendlandt (see bibliography) show at least ten different commercial thermobalances that perform satisfactorily. The basic characteristics of such balances will be illustrated by describing one, the Cahn Electrobalance (Ventron Instruments... 

Finally, further information on the effects of plasma-treatment is given by water uptake properties reported in Table III. Strips of Kevlar cloth treated as shown in the Table, were placed in the Cahn Electrobalance and exposed to water vapor at 30°C to record water uptake characteristics. Comparisons after 1 hr., 10 hr. and 24 hr. exposure are shown. Included in the experimental sequence were cloth specimens which had been plasma-treated at a substrate temperature, Tg, near 200°C. Plasma polymers of HMDSO produced in this temperature range had been shown previously (8) to adhere more tenaciously to substrates then pol3miers formed at lower experimental temperatures. The data show firstly that the hydrophile/hydrophobe balance of Kevlar... 

The Balance. Figure 14 shows a schematic of the Cahn electrobalance (38) most frequently used in thermogravimetiy work (arrangement 1). A photodetection system monitors the beam position. If the beam moves from the horizontal, enough current flows to the torque motor to move the beam back to its original... 

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