Weight contacting plates

Fig. 11. Schematic of PSTC holding power test. 1, plate 2, one square inch of tape contacting plate 3, weight 4, absorbent pad.

The basic observation is that a thin plate, such as a microscope cover glass or piece of platinum foil, will support a meniscus whose weight both as measured statically or by detachment is given very accurately by the ideal equation (assuming zero contact angle) ... 

Derive the equation for the capillary rise between parallel plates, including the correction term for meniscus weight. Assume zero contact angle, a cylindrical meniscus, and neglect end effects. 

The saddles must be designed to withstand the load imposed by the weight of the vessel and contents. They are constructed of bricks or concrete, or are fabricated from steel plate. The contact angle should not be less than 120°, and will not normally be greater than 150°. Wear plates are often welded to the shell wall to reinforce the wall over the area of contact with the saddle. 

The observed weight w of the meniscus must equal the upward force provided by the surface. This, in turn, equals the vertical component of 7—7 cos 0, where 0 is the contact angle —times the perimeter of the plate P since surface tension is a force per unit length of surface edge. Therefore, at equilibrium,... 

Next, an experiment such as that shown in Figure 7.2b could be conducted. The apparatus consists of a pair of Wilhelmy plates attached to two arms of a balance. One plate contacts the clean surface and the other the surface with the monolayer. Note that the barrier separates the two portions of surface. The surface tension will be different in the two regions, and the weight (and volume) of the meniscus entrained by the plate will be larger for the clean surface... 

Only three of the metals, rhodium, palladium and platinum, need be considered. Of these only rhodium plating is of significant commercial importance, but the relatively low cost of palladium has made it attractive for contacts and printed circuits. Electrodeposited platinum is harder than the annealed bulk metal and finds applications in jewellery, the plating of scientific instruments, standard weights and parts of electrical apparatus. 

When used as a detachment method (Figure 4.5a), the container holding the liquid is gradually lowered and the pull on the balance at the point of detachment is noted. For a plate of length jc, breadth y and weight W, assuming zero contact angle,... 

Fig. 40 the anode has a lug pressed by its weight against a copper strip conductor analogously the contact of the cathode plate is obtained by means of the yoke a and carrier bar b. 

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