Vacuum measurement without mercury

A monolithic sample of precipitated silica wrapped under vacuum in a parafilm membrane was measured by mercury porosimetry until a 200 MPa pressure. Figure 3 shows the volume versus pressure curve compared to the curve of the sample without membrane. The mercury porosimetry curves of a sample wrapped in a tight membrane amd the same material without membrane are identical between 1 and 40 MPa. It confirms that the mechanism of volume variation in this pressure domain is truly crushing without intrusion. At pressures above 45 MPa, the two curves are very different as expected because the two mechanisms are different for the sample wrapped in a membrane, the only possible mechanism is the crushing whereas it has been shown that the sample without membrane is invaded by mercury at pressures above 45 MPa. The weak difference between curves observed between 0.1 and 1 MPa can be attributed to a lack of suppleness of the membrane which cannot fit the rough surface of the monolithic sample of precipitated silica fi om the lowest pressures. The volume differences between the two curves which appear progressively below 1 MPa corresponds to the volume comprised between the surface of the sample and the membrane. This volume is... 

The synthesis is carried out in a 500-ml., single-necked, round-bottomed flask which is connected to a standard vacuum line by means of a stopcock adapter. The stopcock adapter is important, since it allows for the easy attachment and removal of the reaction vessel from the vacuum line without exposing the contents of the reactor to air. The vacuum line must be equipped with a mercury manometer in order to measure the pressure of PH3 during the preparation of the Li[Al(PH2)4] solution. A conventional vacuum line with greased stopcocks is satisfactory. However, germyl-phosphine does attack conventional stopcock lubricants so a greaseless system is preferred if available. 

ESR spectra were recorded on a JEOL JES-RE2X spectrometer. About 250 mg of ruthenium-free titanate samples was subjected to heat treatment either in vacuum at 573 K or in a hydrogen atmosphere at 973 K. For measurements of ESR spectra, 30 Torr of O2 or N2O was introduced at room temperature and then cooled to 77 K without evacuation. The spectra were obtained in the dark and under UV irradiation with a 500 W low pressure mercury lamp. 

Materials and Methods. The isomeric compositions of the four polybutadienes used are listed in Table I. Samples were prepared for infrared measurement from solutions of the polymer without further purification. Most films were cast from carbon disulfide solutions on mercury or on glass plates, but a few films were cast from hexane solutions to determine whether or not the solvent affected the radiation-induced behavior. No difference was observed for films cast from the different solvents. The films were cured by exposure to x-rays in vacuum. (Doses were below the level producing detectable radiation effects.) They were then mounted on aluminum frames for infrared measurements. The thicknesses of the films were controlled for desirable absorbance ranges and varied from 0.61 X 10 s to 2 X 10 3 cm. After measuring the infrared spectrum with a Perkin-Elmer 221 infrared spectrophotometer, the mounted films were evacuated to 3 microns and sealed in glass or quartz tubes (quartz tubes only were used for reactor irradiations). 

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