Standard glass filters

Procedure Determine the absorbance of the Sample Preparation with a suitable spectrophotometer in a 1-cm cell at 460 nm, using acetone as the blank. Record the value obtained as A . In the same manner, determine the absorbance of a National Institute of Standards and Technology Standard Glass Filter 930, and record the value obtained as Ap. 

UV levels decline rapidly outside the region of direct sunlight inside a room therefore, the ratio of UV/visible exposure recommended is less than that in standard glass-filtered daylight ID-65 (Clarke, 1979 ISO 10977 1993(E)) for which... 

The testing standard DIN 53 387 (DIN 53 387, 1989) requires the UV spectral distribution in the UV to be 3 + 0.5% (320 to 360 nm) and 6 1% (360 to 400 nm), where 100% is the total irradiance over 300 to 800 nm this corresponds accurately to standard glass-filtered daylight. This distribution is not essential for pharmaceutical product testing sources close to or meeting this standard can be used with confidence, but they will provide a greater UV exposure than necessary (ca. 540 Wh m 2 per 1.2 million lx h). When reproducibility of results between laboratories is important, the spectral distribution of the sources used should be as nearly identical as possible, irrespective of whether they conform to any particular specification. 

Pipette 25.0 mL of the bromide ion solution (0.01-0.02M) into a 400 mL beaker, add excess of dilute silver nitrate solution, filter off the precipitated silver bromide on a sintered glass filtering crucible, and wash it with cold water. Dissolve the precipitate in a warm solution prepared from 15 mL of concentrated ammonia solution, 15 mL of 1M ammonium chloride, and 0.3 g of potassium tetracyanonickelate. Dilute to 100-200 mL, add three drops of murexide indicator, and titrate with standard EDTA (0.01 M) (slowly near the end point) until the colour changes from yellow to violet. 

The NIST material SRM 1866a consists of a set of three common bulk mine-grade asbestos materials chrysotile, amosite and crocidolite, and one glass filter sample. SRM 1867 consists of a set of three imcommon mine-grade asbestos materials antophyllite, tremolite and actinohte. The optical properties of SRMs 1866a and 1867 have been characterized so that they may serve as primary calibration standards for the identification of asbestos types in building materials. 

An industrial standard method has been developed to test the lightfastness of polymers in accelerated test equipment [103]. The apparatus consists of a quartz-xenon tube with a special optical filter between the light source and the specimen to produce light that resembles window glass-filtered daylight [104], Samples are mounted at a specific distance from the arc and are supported on a frame which revolves around the arc 1 to 5 times per minute for uniform exposure. A blower unit in the base provides a flow of air which makes it possible to maintain a black panel temperature of 45°C, measured by a black panel thermometer which is positioned at level with the samples. A black panel unit consists of a bimetallic thermometer mounted on a steel frame. Both faces of the frame plate and also the stem of the thermometer are coated with a heat-resistant glossy black enamel. The relative humidity level in the exposure cabinet is closely controlled. 

Make the standard curve in the range from 10 to 200 pg BSA. Drop samples and standards onto small sheets of glass filter paper (e.g., Whatman GF/A the sheets are labeled with a pencil). Stain the sheets with Soln. A for 20 min and destain with C until the background is nearly colorless. Extract the sheets with 2.0 ml of Soln. D each after drying and measure the resulting blue solution as described above. 

Determination of Hot Melt — Visually. Weigh accurately a 1 g sample of HBX into a tared sintered glass filtering crucible, medium porosity, 30-ml capacity. Using approx 5ml of ethylene chloride, divided into 5 equal portions, 1 min contact time each, extract sample on a Fisher filtrator with water vacuum. Collect filtrate in a 50-ml volumetric flask and dilute to the mark with ethylene chloride. Compare the color of the filtrate visually with previously prepd standards to det the weight of hot melt present. The prepn of the hot melt standard solns are described in 4.4.3.5.14... 

Table 10.7. Standard Values for the NIST SRM 930-e Series Glass Filters (10%,...

Glass Filters as a Standard Reference Material for Spectrophotometry Selection, Preparation, Certification and Use of SRM 930 and 1930, NIST Spec. Publ. 260-116, 1994. 

These data were obtained by die National Institute of Standards and Technology (USA) while developing a transfer standard for verification and calibration of die v-axis of NIR speedometers. Optical filters were prepared from two separate melts, 2035 and 2035a, of a rare eardi glass. Filters from both melts provide seven well-suited adsorption bands of very similar but not exactly identical location. One filter, Y, from one of die two melts was discovered to be unlabelled. Four 2035 filters and one 2035a filter were available at die time of diis discovery. Six replicate speeda were taken from each filter. Band location data from these spectra are provided below, in cm-1. The expected location uncertainties range from 0.03 to 0.3 cm-1. 

Procedure Add 0.1 g of diatomaceous earth to a 60-g sample, agitate for 2.5 min at room temperature (or 10° to 15° above the melting point if the sample is not liquid), and filter. Adjust the temperature to 25° to 35° (or not more than 100 above the melting point), and fill the color tube to the desired mark. Place the tube in the tintometer (in a dark booth or cabinet), and match the sample color as closely as possible with a standard glass. 

For color measurement, twice-a-shift calibration normally uses just a black fight trap and a white standard. This practice cannot provide NIST traceability and no true verification of accuracy is currently available. In early spectrophotometers, a set of colored glass filters calibrated by the National Bureau of Standards (NBS) was commonly used for wavelength and photometric verification. The calibration... 

Exposure of Bleached Pulp. Bleached pulp, based on 50% hardwood and 50% softwood kraft, jordaned to a Canadian standard freeness of 300-350 mL, was kindly supplied by Andrew Chase of the University of Maine. Unaged handsheets made from this pulp contained 85% a-cellulose (3) and 5% hot-1%-alkali-soluble matter (4). In the experiment illustrated in Figure 1, sheets were exposed in the Atlas 6500-W xenon-arc Fade-ometer equipped with Pyrex-glass filters the air temperature was 31 °C, and the relative humidity was 27% the black-panel temperature was 65 °C. Halfway through the reported period of... 

The checker reports that standard filtration techniques can be substituted for the centrifugation steps. The reaction of hydrous niobium (V) oxide is done in a 100-ml. round-bottomed flask fitted with an outer standard-taper joint. The solution of niobium(V) chloride in thionyl chloride is filtered by attaching a filter tube (having a standard-taper inner joint at each end) with a medium-porosity sin-tered-glass filter to the neck of the reaction flask, attaching another 100-ml. round-bottomed flask to the opposite end of the filter tube, and inverting the assembly. The residue can be washed with small aliquots of thionyl chloride. With this kind of apparatus the synthesis can be scaled up by a factor of 10 or more. 

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