PS type type tests


The experimental method in most common use is to heat a small amount (about 1 mg.) of the substance in a capillary tube attached to a thermometer which is immersed in a suitable bath of liquid, and to determine the temperature at which melting occurs. The capillary melting point tubes are prepared either from soft glass test-tubes or from wide glass tubing (ca. 12 mm. diameter). A short length of glass tubing or glass rod is firmly fused to the closed end of the test-tube. The test-tube (or wide glass tubing) must first be thoroughly washed with distilled water to remove dust, alkali and products of devitrification which remain on the surface of the glass, and then dried. The closed end of the test-tube is first heated whilst being slowly rotated in a small blowpipe flame the glass rod or tube is simultaneously heated in the same manner (Fig. 11,10, 1, a). When the extremities of both pieces of glass are red hot, they are firmly fused together, twisting of the joint being avoided, and then  [c.75]

The absorption tubes R and S are next joined together by a 20 mm. length of impregnated rubber tubing, the side-arms forming a glass-to-glass join inside the rubber the side-arm at the non-absorbing end of the tube R being attached to the side-arm of the absorbing end of the tube S. The exit of the tube S is now attached to the guard tube V in the usual way and the pair of tubes finally attached by a 15 mm. piece of impregnated tubing, and glass-to-glass joint, to the beak of the combustion tube. As short a piece of tubing as is compatible with a gas-tight join is used for this connection so that as much as possible of the beak of the combustion tube and of the side-arm of R may be heated directly by the heating hooks Q attached to the thermostatic mortar. These hooks are next placed in position, both initially being on the combustion tube beak between the mortar and the rubber connection to the tube R.  [c.478]

Desired Test Type of Test duration,  [c.244]

Desired Test Type of Test duration,  [c.244]

Since the geometry of the wheel is also displayed during this type of test, it is important to distinguish between defects and geometrical influences. The tester can easily and reliably make these distinctions, if the distortions of the wheel s geometry and the display of the defects caused by the display of the test system are not to great.  [c.307]

As anode and cathode of the tube have to share the same vacuum envelope, and the insulating material has to insulate the high tension between these respective electrodes, the material is always part of the vacuum envelope of the tube. Therefore, the insulator has to be vacuum tight and must be able to carry the atmospheric pressure, which loads this envelope.  [c.533]

In NDT the key question is the reliability of the methods, verified by validation. Regarding the visual methods, the reliability, that means probability of the visual recognition depends on the optical abilities of the scene with the objects. These abilities were determined quantitatively with an image-processing system for fluorescent magnetic particle inspection. This system was used, determining quality of detection media, following the type testing of the european standard prEN 9934-2. Another application was the determination of the visibility in dependance of the inspection parameters as magnetization, application of the detection medium, inclination of the test surface, surface conditions and viewing conditions. For standardized testing procedures and realistic parameter variations the probability of detection may be determined on the basis of physiological lightening in dependance of the defect dimensions.  [c.669]

Probe Type Test Frequency  [c.904]

Run into a test-tube from a micro-burette 0 25 ml. of aniline and 0-5 ml. of the i i acetic acid-acetic anhydride mixture. Insert a cold finger (Fig, 35, p. 62) into the lip of the test-tube, without using a cork. Circulate the water through the finger and gently boil the mixture for 5 minutes. Cool, add about 5 ml. of cold water, stir well with a thin glass rod and filter off the precipitated acetanilide using the apparatus shown in Figs. 45 or 46 (p. 68). Use the filtrate to effect the complete transfer of all the solid from the test-tube to the filter funnel, and then wash the solid with about 1 ml. of ice-cold water and drain thoroughly. Recrystallise from boiling water (about 8 ml.). Filter if necessary while hot through a very small fluted filter paper (or using the apparatus shown in Fig. 47, p. 68) into a small conical flask or test-tube. When quite cold filter off the purified acetanilide, again using the apparatus shown in Figs. 45 or 46. Yield, o-2 g.  [c.108]

Sodium benzoate,—Burns with great difficulty, and after prolonged heating leaves a white infusible residue of NajCOj. Scrape this residue into a test-tube, and test for carbonate in the usual way. Typical of alkali salts of carboxylic acids.  [c.319]

The sodium fusion and extraction, if performed strictly in accordance with the above directions, should be safe operations. In crowded laboratories, however, additional safety may be obtained by employing the follow ing modification. Suspend the hard-glass test-tube by the rim through a hole in a piece of stout copper sheet (Fig. 69). Place 1 -2 pellets of sodium in the tube, and heat gently until the sodium melts. Then drop the organic compound, in small quantities at a time, down — =. the tube, allowing the reaction to subside after each addition before the next is made. (If the compound is liquid, allow two or three small drops to fall at intervals from a fine dropping-tube directly on to the molten sodium.) Then heat the complete mixture as before until no further reaction occurs.  [c.322]

Mix 3 g. of starch well with loml. of water in a test-tube and pour the mixture into 90 ml. of boiling water contained in a 300 ml. conical flask, stirring at the same time. Cool to about 70 and then place in a water-bath maintained at 65-70 , but not higher. Now add 2-3 ml. of the malt extract prepared as above, mix well and allow the hydrolysis to proceed. Take a series of test -tubes and in each put 10 ml. of water and 2 drops of a 1 % iodine solution. At intervals of about 4 minutes (depending upon the activity of the enzyme solution), remove 1 ml. of the reaction mixture, cool and add it to one of the test-tubes and note the colour obtained. At the beginning of the experiment the colour will be blue due to the starch alone. As the reaction proceeds, the colour gradually becomes violet, reddish, yellowish and finally colourless.  [c.513]

Cholestenone. Place a mixture of 1 0 g. of purified cholesterol and 0-2 g. of cupric oxide in a test-tube clamped securely at the top, add a fragment of Dry Ice in order to displace the air by carbon dioxide, and insert a plug of cotton wool in the mouth of the tube. Heat in a metal bath at 300-315° for 15 minutes and allow to cool rotate the test-tube occasionally in order to spread the melt on the sides. Warm with a few ml. of benzene and pour the black suspension directly into the top of a previously prepared chromatographic column (1) rinse the test-tube with a little more benzene and pour the rinsings into the column. With the aid of shght suction (> 3-4 cm. of mercury), draw the solution into the alumina column stir the top 0 -5 cm. or so with a stout copper wire to  [c.944]

Fractional Distillation. For this type of distillation, the fractionating column is inserted vertically between the flask containing the boiling liquid and the condenser. The principle of a fractionating column is that, as the vapours ascend the column from the boiling mixture below, the higher-boiling components are condensed and returned to the flask, the ascending column of vapour being thus steadily scrubbed by the descending column of liquid condensate. The ascending column of vapour becomes therefore steadily richer in the lowest-boiling component, and the descending column of condensate steadily richer in the highest-boiling component. It follows that the prime factor which determines the efficiency of a column is the extent to which the vapour is scrubbed by the condensate, and columns are therefore designed to make this scrubbing as intimate as possible. Text-books of theoretical organic chemistry frequently illustrate remarkable and weird types of fractionating column which the practical chemist never encounters. For actual use in the laboratory two types of column are recommended. (A) For quick rough separations, or (more particularly) for the separation of two components having a considerable difference in boiling-point, the pear column (Fig. h(a)) is useful. The increase in cooling surface produced by pear-shaped bulbs causes considerable condensation, and the condensate, steadily dripping down from the lower shoulder of each bulb, comes in moderate contact with the ascending vapour. The efficiency of a column can, of course, be increased by increasing the number of bulbs in the column. (B) For accurate work, the column shown  [c.25]

Run into a test-tube from a micro-burette 0-25 ml. of aniline and 0 5 ml. of the 1 1 acetic acid-acetic anhydride mixture. Insert a cold finger (Fig, 35, p. 62) into the lip of the test-tube, without using a cork. Circulate the water through the finger and gently boil the mixture for 5 minutes. Cool, add about 5 ml. of cold water, stir well with a thin glass rod and filter off the precipitated acetanilide using the apparatus shown in Figs. 45 or 46 (p. 68). Use the filtrate to effect the complete transfer of all the solid from the test-tube to the filter funnel, and then wash the solid with about 1 ml. of ice-cold water and drain thoroughly. Recrystallise from boiling water (about 8 ml.). Filter if necessary while hot through a very small fluted filter paper (or using the apparatus shown in Fig. 47, p. 68) into a small conical flask or test-tube. When quite cold filter off the purified acetanilide, again using the apparatus shown in Figs. 45 or 46. Yield, o-2 g.  [c.108]

Sodium benzoate.—Burns with great difficulty, and after prolonged heating leaves a white infusible residue of NajCOj. Scrape this residue into a test-tube, and test for carbonate in the usual way. Typical of alkali salts of carboxylic acids.  [c.319]

The sodium fusion and extraction, if performed strictly in accordance with the above directions, should be safe operations. In crowded laboratories, however, additional safety may be obtained by employing the following modification. Suspend the hard-glass test-tube by the rim through a hole in a piece of stout copper sheet (Fig. 69). Place 1-2 pellets of sodium in the tube, and heat gently until the sodium melts. Then drop the organic compound, in small quantities at a time, down — the tube, allowing the reaction to subside after each addition before the next is made. (If the compound is liquid, allow two or three small drops to fall at intervals from a fine dropping-tube directly on to the molten sodium.) Then heat the complete mixture as before until no further reaction occurs.  [c.322]

Beatings used on fans may be either sleeve or antifriction type and must be designed to withstand loads resulting from dead weight, unbalance, and rotor thmst and be able to operate at the iatended maximum speed without excessive heating (see Bearing materials). When natural convection from the beatings is iaadequate, some other cooling method must be provided. Lubricating oil may be circulated through an external cooler, or the pillow blocks may be cored with passages for forced circulation of air or water. Fans operated at high temperatures iacrease the beating cooling problem caused by heat conduction along the shaft. A small external fan wheel on the shaft, called a heat slinger, is frequently provided, or forced-circulation water cooling is used. In addition to the beatings of fans operating on hot, low density gas at high pressure rise, special attention is needed to ensure high rigidity of the wheel and shaft. Fan wheels should be balanced both statically and dynamically, eg, ia the field with chalk and weights (15). Elaborate electronic test instmments are also available. An unbalanced condition causes a vibrational displacement of the beatings which is frequently checked. Table 2 fists typical displacements of fans operating at various speeds and various degrees of unbalance.  [c.109]

Spinel Ferrites. Prefiring is usually carried out in an air atmosphere in a continuous rotary kiln. In such a kiln the material is transported through a heat zone typically of 900—1100°C, in a rotating tube inclined at a small angle, which transports the powder downward along its length by a tumbling action. The angle is predesigned for a proper heating time and an economical throughput. When the mixture of raw materials enters the heat zone, carbonates and higher oxides decompose and a sequence of soHd-state reactions occurs, starting with the formation of Zn-ferrite and ending with the formation of the desired MnZn-ferrite or NiZn-ferrite (83). Usually the aim is not a 100% spinel stmcture after prefiring. A 50—80% one usually suffices because the remaining conversions take place during the final sintering process after the forming step. Too high prefiring temperatures would result in considerable shrinkage in this stage, which makes the ferrite hard and thus difficult to mill. The prefired powder is characterized by x-ray diffraction, by the BET specific surface or the Fisher number, and sometimes by the inductance of a coil wound on a toroid pressed from the prefired powder. The prefired and subsequendy milled powder has to be such that it results in a predictable and very constant shrinkage of pressed products during final sintering, in order to satisfy tight demands normally imposed on final product dimensions or to be able to realize these dimensions by grinding.  [c.194]

One advantage of the impedance tube test methods is the small (usually <10 cm (4 ia.) dia) size of the test samples. For these tests sound impinges on the test sample only at normal iacidence to the surface, and the sound-absorption coefficients derived ia this manner are vaUd only at this angle.  [c.312]

Magnetic flux leakage (MFL) imaging appears to have originated with the use of high speed computer processing of MFL detected by coil sensors rotating around the outer surface of oil-field tubes (37) for the detection of new tube flaws. The results are presented on a fold-out two-dimensional map of the pipe, so that the flaws are shown in their tme locations. Whereas the severity of the flaws is not assessed by this technique, the length and angle to the pipe axis is recorded so that the inspector may more easily perform prove-up. The imaging of the flaw locations, along with use of noise reduction algorithms, also permits clearer detection of inner surface imperfections, and thus indicates that the sensitivity of the technique should be raised. Typically 5% deep electrical discharge machined (EDM) test notches can be detected on the internal diameter surface in 9.5 mm (0.375 in.) wall thickness.  [c.132]

Traditionally, glass has been the preferred container material. The USP has adopted a classification of glass types acceptable for dmg container use Type I, borosihcates glass Type II, a soda—lime treated glass Type III, a soda—lime glass and NP (nonparenteral), a soda—lime glass that is not suitable for parenteral products. There are two official USP tests the powdered glass and the water attack test. In general. Type I glass is preferred it is expensive, however. Types II and III may also be used for parenteral products.  [c.234]

Globe valves have a body configuration (Fig. 2c) that causes the flowing fluid to take an S-shaped path through the valve body. Needle valves generally have a similar internal flow configuration, whereas angle valves cause the flowing fluid to take an L-shaped path. These valves have higher pressure losses than gate, plug, or ball valves angle valves generally lose less pressure than globe or needle valves. These valves are used for flow control, with the seat and disk or needle configuration selection based on the degree of control required. A flat composition disk and a flat seat or a slightly tapered metal disk and seat are used when close control, particularly near the shutoff position, is not required. When close control is required at all positions, a long taper plug-type disk and long taper seat are used. For fine control, the long taper plug-type disk is replaced by a long tapered cone and the valve is referred to as a needle valve. Butterfly valves (Fig. 3) more closely resemble gate valves than globe valves because flow is controlled by means of a disk positioned across the flow passage for shutoff or parallel to the direction of flow for the wide-open position. Only specially designed butterfly valves provide tight shutoff and their control characteristics are somewhat poorer than desired. However, in situations where flow control of large gas volumes is required and pressure loss must be minimized, the butterfly valve has no competition. The diaphragm or pinch-clamp valve affects closure by a resiUent mbber-like diaphragm pressing down on a transverse weir (Fig. 4). A relatively clean sweep of fluid through the valve and over the weir minimizes pressure drop. Crevices and corners are also minimized, which prevents buildup of precipitates or soHd deposits. Diaphragm valves are employed where the valve mechanism must be isolated from the fluid or where the fluid contains soflds and a tight closure is required. In this type of valve, the diaphragm acts as closing medium as well as sealing gasket. The diaphragm valve is used widely in the food and beverage industry and under corrosive conditions. It is limited to ca 90°C and 1.0 MPa (145 psi), depending on the material of constmction. The body can be made of standard materials the flexible diaphragm, however, must withstand the limits of temperature and pressure.  [c.56]

Jptt 15,353 (Aug. 20, 1963), H. Tabe (to Takeda Chemical Industries, Ltd.).  [c.144]

Indicators can determine if uniform steam penetration has been achieved during a Bowie Dick-type test. Produced in the form of sheets (23 X 30 cm), chemical indicators are capable of uniform color change over their entire surface when exposed to pure saturated steam under test conditions. Nonuniform color development is an indication of failure of the test. U.S. and international stands for the performance and accuracy of chemical indicators have been pubHshed (13,14).  [c.408]

General Toxicology Studies. Studies may be conducted ki Hve specimens in vivo) or ki test tubes in vitro). Eor reasons inherent in both the toxicity assessment procedure and the design of studies, it is usual to proceed in sequence from acute to the various stages of multiple-exposure studies. Acute studies give information on the type of toxic injury produced by a single exposure, including the effects of massive overexposure. The fact that a particular type of toxic injury is not produced by an acute exposure does not necessarily imply the absence of potential for that type of injury by the chemical, since multiple exposures may be necessary to induce the effect. However, effects produced by acute or relatively short-term repeated exposure may also be produced by longer-term repeated exposures, and at lower concentrations. Hence, in addition to giving information on potential for toxicity, the acute and short-term repeated studies are used to give guidance on exposure conditions to be followed in longer-term repeated exposure studies. The type of monitoring to be employed will depend on a variety of considerations, including the chemistry of the material, its known or suspected toxicology, the degree of exposure, and the reason for conducting the test. In general, since the multiple exposure studies are more likely to produce the widest spectmm of toxic effects, it is usual to employ the most extensive monitoring in these studies.  [c.235]

Tappi Test Methods", Tappi Press, Atianta, Ga., 1994.  [c.312]

Since oxygen uptake is tested in a closed system, loss of volatilization is minimal. This type of test is not reUable for estimating service life under conditions in which the polymer is exposed to air movement.  [c.234]

The absorption tubes R and S are next joined together by a 20 mm. lengfh of impregnated rubber tubing, the side-arms forming a glass-to-glass join inside the rubber the side-arm at the non-absorbing end of the tube R being attached to the side-arm of the absorbing end of the tube S. The exit of the tube S is now attached to the guard tube V in the usual way and the pair of tubes finally attached by a 15 mm. piece of impregnated tubing, and glass to-glass joint, to the beak of the combustion tube. As short a piece of tubing as is compatible with a gas-tight join is used for this connection so that as much as possible of the beak of the combustion tube and of the side-arm of R may be heated directly by the heating hooks Q attached to the thermostatic mortar. These hooks are next placed in position, both initially being on the combustion tube beak between the mortar and the rubber connection to the tube R.  [c.478]

Toxicity may be one of the most difficult properties to model, especially for high-throughput screening in the drug discovery process. The difficulties arise from the following facts The effects of toxicants are species-specific, organ-specific, and time-dependent (i.e., acute effects differ from chronic effects). This has the consequence that the concentration at which adverse effects occur can vary over several orders of magnitude depending on the spedes and the type of test. A comprehensive overview of modeling toxidty has been published by Schultz et al. [34], and another one addressing more specific issues of eco-toxicology by Escher and Hermens [35]. The topic of expert systems will not be discussed here a critical review of aU the major systems used today has been published by Benigni and Richard [36].  [c.504]

When the cutoff is sharp, discontinuities in the forces and resultant loss of con servation of energy m molecular dynamics calcnla-tionscan result.To minimi/e edge effects of a cu toff, often theciit-off IS implemented with a switching or shifting function to allow the interactions to go smoothly to /ero.  [c.181]

The choice of solvent cannot usually be made on the basis of theoretical considerations alone (see below), but must be experimentally determined, if no information is already available. About 0 -1 g. of the powdered substance is placed in a small test-tube (75 X 11 or 110 X 12 mm.) and the solvent is added a drop at a time (best with a calibrated dropper. Fig. 11, 27, 1) with continuous shaking of the test-tube. After about 1 ml. of the solvent has been added, the mixture is heated to boiling, due precautions being taken if the solvent is inflammable. If the sample dissolves easily in 1 ml. of cold solvent or upon gentle warming, the solvent is unsuitable. If aU the solid does not dissolve, more 11,27,1. solvent is added in 0-5 ml. portions, and again heated to boiling after each addition. If 3 ml. of solvent is added and the substance  [c.124]

Equip a 1-litre round-bottomed flask with a reflux condenser and a dropping funnel (compare Figs. II, 13, 9 and III, 71, 1). Prepare a mixture of 150 g. of finely powdered acetamide and 100 g. of powdered phosphorus pentasulphide quickly, transfer it rapidly into the flask and immediately add 100 ml. of dry benzene. Set up the apparatus in a fume cupboard. Prepare a mixture of chloroacetone (b.p. 118-120° CAUTION—the compound is lachrymatory) and 75 ml. of dry benzene place it in the dropping funnel and insert a calcium chloride drying tube in the mouth. Add about 10 ml. of the chloroacetone-benzene mixture to the contents of the flask and warm gently on a water bath remove the water bath immediately the exothermic reaction commences. Introduce the remainder of the chloroacetone in ea. 10 ml. portions at such intervals that the reaction is under control. When all the chloroacetone has been added, reflux the mixture on a water bath for 30 minutes. Then add 400 ml. of water to the reaction mixture with shaking after 20 minutes, transfer the eontents of the flask to a separatory funnel, run oflF the lower layer into a beaker and discard the reddish upper layer containing the benzene. Make the lower layer alkaline by the addition of 20 per cent, sodium hydroxide solution test the highly coloured aqueous solution (and not the dark dimethylthiazole floating on top of the liquid) with phenolphthalein paper. Separate the black upper layer of crude dimethylthiazole with 50 ml. of ether, and extract the aqueous layer with five 60 ml. portions of ether. Dry the combined ethereal extracts over anhydrous magnesium sulphate, and filter through glass wool. Remove the ether by distillation from a steam bath using a Claisen flask with fractionating side arm (compare Fig. II, 13, 4 insert a calcium chloride drying tube into the dropping funnel since the thlazole is hygroscopic) and fractionate the residue. Collect the fraction boiling at 140-150° and redistil it. The yield of 2 4-di-methylthiazole, b.p. 143-145°, i 115 g.  [c.842]

The following alternative procedure is recommended and it possesses the advantage that the same tube may be used for many sodium fusions. Support a Pyrex test tube (150 X 12 mm.) vertically in a clamp lined with asbestos cloth or with sheet cork. Place a cube (ca. 4 mm. side = 0 04 g.) of freshly cut sodium in the tube and heat the latter imtil the sodium vapour rises 4 5 cm. in the test-tube. Drop a small amount (about 0-05 g.) of the substance, preferably portionwise, directly into the sodium vapour CAUTION there may be a slight explosion) then heat the tube to redness for about 1 minute. Allow the test tube to cool, add 3-4 ml. of methyl alcohol to decompose any unreacted sodium, then halffill the tube with distilled water and boil gently for a few minutes. Filter and use the clear, colourless filtrate for the various tests detailed below. Keep the test-tube for sodium fusions it will usually become discoloured and should be cleaned from time to time with a little scouring powder.  [c.1040]

THPOH—Amide Process. In the THPOH—amide process, the THPC is neutralized to pH 7.2—7.5 with aqueous sodium hydroxide. The specific active species present in solution at this point is not precisely known, but is thought to be a mixture of ttis(hydroxymethyl)phosphine [2767-80-8] (THP) and formaldehyde, or the hemiacetal adduct of these components (86—89). A disadvantage to this system is that an inactive by-product, ttis(hydroxymethyl)phosphine oxide [1067-12-5] (THPO), is frequently formed. A further by-product of this reaction is hydrogen gas. In order to avoid formation of THPO, neutralization of THPC is frequently discontinued at CLpH 7.2. Fabrics given this treatment (THPOH, TMM, and urea) show less stiffness and better tearing strength than are observed for the same fabrics treated with the THPC—amide process. Good retention of breaking strength and less tendency to yellow when exposed to hypochlorite bleach are also observed for this finish (90—92).  [c.489]

Impedance Tube Test Methods. There are two impedance tube test methods ASTM C384-90a (3) and ASTM E1050-90 (4). Test method C384-90a makes use of a tube with a test specimen at one end, a loudspeaker at the other, and a probe microphone that can be moved inside the tube. Sound emitted from the loudspeaker propagates down the tube and is reflected back by the specimen. A standing wave pattern develops inside the tube.  [c.311]

The magnetic leakage field may be detected in several ways, most frequently by a moving conducting cod or sensor, very fine ferromagnetic particles, or recording tape. A moving probe cod or a semiconductor magnetic field detector passing through a leakage field causes a voltage to be generated. The voltage maybe analyzed to determine the presence and characteristics of typical defects. Finely divided, low remanence magnetic particles ate another common technique for indicating flaws. When these particles are appHed to the surfaces of the suitably magnetized test object, they collect where leakage magnetic flux exists at the material surface. These accumulations usually define cracks, porosity, or near-surface submerged cavities. The particles may be coated with lubricants and color dyes or fluorescent materials to aid visibdity. Parts tested using visible dye coatings ate inspected under white light those tested using fluorescent magnetic particles are inspected under near-ultraviolet radiation (365 nm) from a filtered mercury-arc lamp. Typically, wet fluorescent magnetic particles define small discontinuities better than dry particles in visible light. Tests of these types ate often used on piping, tubing, and weld root beads and completed fillet welds on steel stmctures. They also are used widely on jet engine turbine blades made of ferromagnetic materials, including some cobalt-base alloys. In other test systems, repHcation is made of the magnetic field patterns on flexible magnetic recording media. Magnetic recording techniques permit electronic imaging of defects, and provide records that can be stored, transmitted, or reproduced (see Information storage MATERIALS, magnetic). Magnetic leakage flux tests have wide appHcation in industrial inspection. Typical ate tests of longitudinal welds in pipe during fabrication, and oil-fteld equipment, including oil-weU drill pipe, tubing, line pipe, and stmctures. Pipelines (qv) are regularly inspected for thin wall using the magnetic flux leakage principle. Internal inspection devices called pigs are used for inspecting buried pipelines. Similar tests can be made on stmctures and piping in chemical plants and petroleum (qv) refineries.  [c.125]

X-Ray and y-Ray Tests. Radiographic imaging tests (1—6,28) are widely used to examine interior regions of metal castings, fusion weldments, composite stmctures and brazed honeycomb mechanisms, and many other metallic and nonmetaUic components. Radiographic energy, in the form of photons, maybe excited using either an x-ray tube or a radioisotope, such as iridium-192 [14694-69-0] or cobalt-60 [10198 0-0] Co. Higher energy levels penetrate greater thickness of the same material. X-ray energies in the 8—160 kV range penetrate up to 76 mm of light alloys and 6 mm of steel. Radioisotopes such as iridium-192 are used for thinner steel pipe walls or lower density metals. Cobalt-60 is used for steel thickness in the range of 25 to 190 mm. Penetrating radiation, introduced at intensity Iq on the side of the part facing the source or tube, is recorded by film, real-time imaging systems, or by detection gauges on the opposite side (Fig. 6). Anomalies in the path are imaged on the recorded plane, provided that the alignment and exposure are correct. Maximum detection sensitivity occurs for radiography when the significant dimension of the anomaly is oriented parallel to the x-ray beam. Radiographic tests are made on pipeline welds, pressure vessels, nuclear fuel rods, and other critical materials and components that may contain three-dimensional voids, inclusions, gaps, or cracks aligned so that portions are parallel to the radiation beam. Because penetrating radiation tests measure the mass of material per unit area in the beam path, these can respond to changes in thickness or material density, and to inclusions of density different from that of the material in which the inclusions are embedded. The typical film radiographic test sensitivity used in industrial inspection can detect thickness or density differences equal to about 2% of material thickness. For the most critical nuclear and aerospace appHcations, however, specifications may call for demonstration of better contrast sensitivity in such penetrating radiation tests. When cracks foUow irregular paths, some parts of which are aligned with the path of the radiation beam for 2% or more of the total beam path length in the test material, it is possible to visualize the cracks with great clarity if the cracks effectively reduce the thickness of material through which the probing beams must pass. However, x-ray and y-ray film imaging tests are insensitive to cracks, disbonds, and laminar discontinuities that He in planes perpendicular to the radiation beams or to defects representing Httle change in thickness. In extmsions and hot forgings, many discontinuities, which may originally have been three-dimensional voids or discontinuities, are flattened and gready elongated in the deformation process. These discontinuities are usually parallel to the surface of the product and penetrating radiation tests rarely detect such laminar flaws. In fusion-welded pipe and tubing, however, often both the longitudinal welds made in the mill and the circumferential or girth welds made during tubing erection or during the laying of pipelines in the field provide ideal subjects for radiography inspections. In large-diameter pipelines, x-ray or y-ray sources are often propeHed into the open end of the pipeline on crawlers having detectors of girth weld locations for distances of several kilometers. The isotope source traveling on the pipe centerline emits radiation circumferentially, producing an interpretable weld image and a permanent record for further reference.  [c.129]

Most normal starches contain two distinct types of D-glucopyranose polymers. Amylose is an essentially linear polymer of a-D-glucopyranosyl units linked (1— 4) as shown in Figure 1. Although amylose molecules are generally thought of as being linear chains of a-D-glucopyranosyl units, most amylose preparations contain amylose molecules with two to five branches. These long branches allow the molecules to possess nearly the same properties as truly linear molecules. Starch gives a characteristic blue color when stained with iodine, due to insertion of iodine into an amylose heUcal stmcture to form a complex with iodine on the inside of the helix. Amylopectin [9037-22-3] also forms a complex, but its color is purple to reddish brown, depending on the source of the amylopectin (25). In the presence of amylose this color reaction is usually obscured by the amylose—iodine blue. The characteristic blue color of the iodine—amylose complex has been employed both as a qualitative and quantitative test for starch. Amylose [9005-82-7] may be isolated by complete aqueous gelatiuization and dispersion of starch and mixing the hot starch solution with an organic complexing agent such as 1-butanol (26) in water. On cooling, the amylose—butanol complex crystallizes and is removed by centrifugation. Recrystallization of the amylose—1-butanol complex and subsequent removal of the 1-butanol produces a pure amylose. Fractionation of amylose and amylopectin has been reported employing gel filtration chromatography and elution with aqueous sodium chloride (27). However, some starches contain only highly branched molecules. These are termed waxy starches because of the vitreous sheen of waxy com grains when cut. Alternatively, some mutant seed varieties produce starches having up to 85% linear molecules (high amylose starch), although most starches have about 25% linear and 75% branched molecules. Starches high in amylose are subject to significant intermolecular association, leading to what is known as resistant starch (28—30). Resistant starch is that fraction not extracted from dietary fiber unless the sample is treated with dimethyl sulfoxide or alkaU the starch is resistant owing to retrogradation of the amylose. However, other types of resistant starch occur, such as the physically segregated starch in some beans, the ungelatinized B-type starch granules from potatoes or green bananas, and chemically modified starch (30). Resistant, retrograded, high amylose starches find some use as fat replacers in a variety of food types.  [c.341]


See pages that mention the term PS type type tests : [c.46]    [c.509]    [c.835]    [c.76]    [c.76]    [c.331]    [c.1061]    [c.1104]    [c.146]    [c.11]    [c.450]    [c.90]   
Industrial power engineering and applications handbook (2001) -- [ c.4 , c.493 ]