Free glass

All glassware must be scrupulously clean (see Section 3.8), and if it has been standing for any length of time, must be rinsed with distilled or de-ionised water before use. The outsides of vessels may be dried with a lint-free glass-cloth which is reserved exclusively for this purpose, and which is frequently laundered, but the cloth should not be used on the insides of the vessels. 

There are four principal processes that may be used to manufacture the glass body that is drawn into today s optical fiber. "Outside" processes—outside vapor-phase oxidation and vertical axial deposition— produce layered deposits, of doped silica by varying the concentration of SiCl4 and dopants passing through a torch. The resulting "soot" of doped silica is deposited and partially sintered to form a porous silica boule. Next, the boule is sintered to a pore-free glass rod of exquisite purity and transparency. 

Currently available CRMs for Cr(lll)/(VI) species There exist a lyophilized water certified for Cr(III)/Cr(VI) and a binder-free glass fiber filter loaded with welding dust certified for Cr(VI) and total Cr (Vercoutere et al. 1998 Christensen et al. 1999) issued by the BCR. They consist of a set of specimens for single use. There is a need for more CRMs, such as a Cr(VI) in industrial effluents and in river water containing, e.g. humic substances. 

Contamination with endotoxin is an important and frustrating problem in LEH manufacturing for two reasons. Firstly, hemoglobin has a strong tendency to bind endotoxin, where one hemoglobin molecule binds to four endotoxin molecules (K 3.1 x lO M) (117). Secondly, endotoxin has amphiphilicity that enables its stable insertion into lipid bilayer. Such an interaction not only presents contamination and stability problems, but also hampers accurate quantitation of endotoxin. The best possible way to prevent endotoxin contamination is to use aseptic precautions with utmost care. All the machinery, filters, and water should be endotoxin-free. Glass and metallic components may be dry-heat sterilized at about 200° C for three... 

The way in which fluoride is taken up by glass-ionomers has been studied using surface analysis techniques. Dynamic secondary ion mass spectroscopy (SIMS) shows that most of the fluoride becomes concentrated in the surface [248]. Its concentration with depth varies as an error function relationship [248]. X-ray photoelectron spectroscopy (XPS) has suggested that fluoride taken up becomes associated with calcium [249]. However, the form of this association is unclear, because calcium fluoride as such is very insoluble, and when added to a fluoride-free glass-ionomer cement, caused no fluoride to be released [234]. It therefore seems unlikely that the calcium-fluoride association results in formation of Cap2, and further research is necessary to determine the precise nature of the calcium-fluoride association, and thus to resolve this paradox. 

Pool water from all 20 vials into one sterile pyrogen-free container. Vortex to mix. Pipette two aliquots of 0.1 ml each into labeled 10 X 75 mm sterile pyrogen-free glass tubes. 

Pipette duplicate 0.1-ml aliquots from each vial into labeled 10 x 75 mm sterile pyrogen-free glass tubes. Follow steps 10 through 14 in the stopper section of the SOP. Record results. 

Take two 10 x 75 mm sterile, pyrogen-free glass test tubes. 

Furthermore, GC samples were separated on a Carlo Erba type 4200 gas chromatograph fitted with a normal FID and with a flame photometric detector (FPD) operating in the sulfur-mode at 394 nm. Again, the dead-volume free "glass-cap-cross" was used in order to split the carrier gas flow. By means of these sulfur chromatograms mass spectral evaluation could be focussed on certain compounds in very complex mixtures. 

Syringe filter, polypropylene, 25 mm diameter, 0.45micrometer pore size with binder-free glass fiber prefilter Syringe filter, PTFE, 25 mm diameter, 1.0 micrometer pore size Syringe filter) PTFEt 25 mm diameter, 0.45 micrometer pore size Syringe filter LC. 25 mm diameter, 0.45 micrometer pore size Sterilization filter unit, nylon, 200ml, 0.45 micrometer pore size Sterilization Filter Unit cellulose acetate, 0.45 micrometer Sterilization Filter Unit cellulose nitrate 0.45 micrometer... 

Boron-Free Glass Fibres-the Trend for the Future, RP, June 2003. 

FIG. 5.7. (a) Shows the appearance of annealed and tlierefore strain-free glass, (b) Shows the light bands in stiained glass and indicates tlie need for annealing. 

Crystal glasses were traditionally melted in pot furnaces, but nowadays small continuous tank furnaces are used. Lead glasses are conveniently melted in Unit-Melter furnaces, lead-free glasses in all-electric furnaces with a daily output of several tons (cf. Fig. 102). Machine forming is being gradually introduced even for these types of glass. 

Suction machines gather the glass into the mould from free glass surface by underpressure. Much wider application has been achieved by machines working with the... 

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