McBain Bakr spring balance

Apparatus. The sorption of methanol on coal was measured in the apparatus shown schematically in Figure 1. It consisted of three McBain-Bakr tvpe balances, the springs for which were formed from 0.005-inch Ni-Span-C alloy wire annealed at 600°C. The diameters of these springs were about 1.5 cm.,... 

Helical spring balances first used by McBain and Bakr have been extensively used for adsorption measurements. The spring is suspended inside a glass tube by attachment to a hook at the top. A bucket containing the adsorbent is connected to the bottom of the spring. The bottom of the tube, containing the sample, is immersed in the coolant. The upper portion of the tube is connected to a vacuum pump, source of adsorbate, and manometer. 

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. 

A spring balance for the determination of the amount adsorbed (measurement of mass) was first used by McBain and Bakr (1926). In its simplest form the apparatus consists of an adsorbent bucket attached to the lower end of a fused silica spring, which is suspended within a vertical glass tube as in Figure 3.10. 

Water vapour adsorption and desorption isotherms were determined gravimetrically at 298 K with the aid of quartz spring balances of the McBain-Bakr type. Prior to measurement each of the microporous carbons was outgassed at 573 K, the other samples at 673 K, for 16 hours to a vacuum of < 10 torr. The adsorbents used in this study are listed in Table I they have all been employed in other related studies and their properties are described elsewhere (ref. 9). 

Many improvements in design and material have been made since McBain and Bakr s original paper. Gregg and Sing, as well as Young and Crowell, review some of the more recent developments of spring as well as beam balances. 

Figure 3.10. The McBain spring adsorption balance (after McBain and Bakr, 1926).

In another static method of measuring gas adsorption, the amount of gas adsorbed is measured by the increase in the weight of the adsorbent. For this, a very useful balance was developed by McBain and Bakr (Figure 13 2), the essential part of which is a helical spring... 

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