The Bubble Method

As a general rule, there is an economic break-even point at ca 0.08 mm, which coincides with the defined difference between film and sheet. Film is made mote economically by the bubble method and sheet by the tenter-frame method. The exact thickness for break-even depends on technological improvements, which can be made in both processes, in the degree of control used in regulating them and in quaUty requirements. 

A method similar to the falling-ball method is the bubble method. A vial is filled with liquid, leaving sufficient room for a bubble that can equal the diameter of the vial. The vial is inverted and the time required for the bubble to pass two predetermined marks is determined. The viscosity will be directly proportional to the time required for the bubble to rise. 

The bomb method is quite similar to the bubble method except that the constant volume condition causes a variation in pressure. One must, therefore, follow the pressure simultaneously with the flame front. 

Test methods described in the literature inelude the bubble method, helium mass speetrometiy, liquid tracer (dye), head spaee analysis, vacuum and pressure decay, weight loss and gain, and high voltage leak deteetion [6]. 

Immediately following the initial assembly (and at any other time leaks are suspected), the box and purification train should be tested for leaks. A quick test for leaks is to pressurize the dry box until the gloves stick straight out. The gloves should remain in this position for several hours if no leaks are present. If leaks are indicated, testing is most easily accomplished while the box is pressurized. If the inert atmosphere is helium, the preferred method is the helium sniff test. All joints, welds, and connections should be checked. In the absences of a helium-sensitive probe or if the inert atmosphere is other than helium, the bubble method may be used a small amount of soapy water is placed on leak-prone welds and joints and the appearance of any bubbles is noted. 

Figure 5 shows an outline of the experimental appratus. The fused lead was placed in a reaction tube made of quartz. The reaction was studied by the bubbling method in which H2S was bubbled into the fused lead and by a soft blowing method in which H2S was blown onto the surface of the lead. The H2S gas stored in vessel No. 1 was circulated by pump No. 2. Since the lead content was in excess of the H2S in order to maintain the liquid state, the reaction behavior was examined in this experiment until the gas reached the equilibrium composition. 

Figure 6 shows the result obtained by the bubbling method. Since the conversion of the ordinate are in proportion of formed H2 by the reaction, it should reach the same value as the equilibrium H concentration. The value is approximately 99 % at this temperature. 

The results obtained by a gas sweeping method were rather poor compared to those obtained by the bubbling method. In particular, the reaction almost stagnated after a time of about 30... 

Talsma, H., Van Steenbergen, M. J., Borchert, J. C. H., Crommelin, D. J. A. (1994), A novel technique for the one-step preparation of liposomes and nonionic surfactant vesicles without the use of organic solvents. Liposome formation in a continuous gas stream The bubble method,/. Pharm. Sci., 83, 276-280. 

With polymers such as polyvinylidene chloride copolymers and polypropylene the bubble method is carried out in a different way. First a tube is extruded and quenched as rapidly as possible to keep the crystallinity as low as possible. As shown in Fig. 10 the collapsed tube passes through a pair of nip rolls (a) and is then heated to the desired temperature and blown up to a 4-5 times larger diameter before it reaches the next set of nip rolls (b) rotating at a higher speed to provide a longitudinal stretch ratio 1 3-1 4. 

In the bubble method, a standard viscosity tube is filled with a specimen liquid, the temperature of liquid is equilibrated to 25 C in a bath, the level of the meniscus is adjusted to 100 mm line, cork is inserted to end on 108 mm line, sample is hold in thermostating bath for another 20 min. Then the tube is inverted and the time for the bubble to flow from a mark at 27 mm to 100 mm is measured. 

It is evident that the rate constants of ozone interaction with ketone, measured by the static method (Fig. 6) through mixing of ozone and ketone solutions at [K] [03] are higher than those found by the bubbling method (Table 6). This is not difficult to explain because in the former case the obtained values represent the total effective constant of interaction of both the enol and the keto form. 

The kinetics of ozone reactions with ketones is also determined using gas chromatographic analyses. The relative rate constants shown in Table 6, column 4 demonstrate that only acetone and methylketone possess lower reactivity than the standard. It is seen that the rate constants, calculated from the relative values and the value of the standard constant correspond to those found by the bubbling method. The main products of ozone interaction with methylethylketone are 2-hydroxymethylethylketone, diacetyl, peroxides - alkyl and hydro, acetaldehyde and AcAc. 

The dynamic surface tension of [3-casein solutions at three concentrations 5 10, 10 and 10 mol/1 are shown in Fig. 14. As one can see the results from the two methods differ significantly. For the bubble the surface tension decrease starts much earlier. The surface tensions at long times, and hence the equilibrium surface tension from the bubble experiment are lower than those from the drop. However, the establishment of a quasi-equilibrium for the drop method is more rapid at low (3-casein concentrations while at higher P-casein concentrations this process is more rapid for the bubble method. This essential difference between solutions of proteins and surfactants was discussed in detail elsewhere [50]. In brief, it is caused by simultaneous effects of differences in the concentration loss, and the adsorption rate, which both lead to a strong difference in the conformational changes of the adsorbed protein molecules. 

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