Standard hardness

For examination of X-Ray images the customer needs standard hard- and software as given in table 4 and 5. As mentioned before the directory can be customised to specification defined by the customer. 

As with all tests, frequent caUbration of the test equipment using standard hardness blocks is a prerequisite for rehable hardness testing (see ASTM E18). Standard hardness blocks are available through commercial sources in the United States but do not have traceabiUty to internationally accepted standards as in Europe. 

There are literally many thousands of chemical compounds that are potential air pollutants. It would be impossible to present all the pertinent data and information needed to evaluate each and every air pollution scenario. There are, however, a wealth of information and data bases that are available on the worldwide Web, along with a number of standard hard copy references to obtain information on the chemical and physical properties, and health risks of potential atmospheric contaminants. 

Depth of penetration Rockwell superficial and Rockwell standard hardness tests... 

The standard briefly covers the significance of hardness in terms of its relation with modulus, and the practical use of hardness tests. The hardness tests for rubber that are standardized by ISO are introduced and the distinction between dead load and durometer type instruments is explained to help with selection of a test method for particular circumstances. The effect of test piece, use of standard hardness blocks and comparison of hardness scales is also outlined. 

It has been stated previously that hardness readings are influenced by test piece thickness. Consequently, the term standard hardness refers to measurements made on standard test pieces, and measurements on non-standard test pieces are called apparent hardness. 

Going further in these attempts and analysing the results of Vickers hardness measurements (Hv) obtained for particular standard hardness blocks of the Mohs scale, Khrushchev (1950) tried to find a mathematical relationship between these values. To this end, he had to eliminate the existing discontinuities between particular degrees of Mohs hardness (Fig. 4.2.1, old scale). He attained this by augmenting the scale with five extra... 

Fig. 4.4.11. Abrasiveness of standard hardness blocks of traditional Mohs scale and modified by Povarennykh.

As equivalent to the Mackensen air blower, ultrasonic devices can be used, specifically those manufactured by Rio Grande and Branson (Fig. 4.4.18). With a suitably chosen nozzle delivering the abrasive material and with the device scaled on Mohs standard hardness blocks, small surfaces can be tested by the point abrasion method using ultrasonic impact abrasion technique. The possibility of employing a fine-grained abrasive for this purpose allows substantial miniaturization of measurement, as compared with Mackensen s method. 

The standard hardness blocks are too thick to reach equilibrium in the normal test period, so the hardness readings are taken on a stack of 2-mm-thick pieces. 

For higher-velocity ammunition the hardness of the brass usually decreases from the base to the neck of the cartridge case. Cartridge cases for low-velocity ammunition are normally made to a standard hardness along their entire length. 

It is suggested that the standard soft water should contain 34.2mg/kg calculated as calcium carbonate (WHO standard water), not 20.0mg/ kg (CIPAC standard water) and that the preparation of WHO standard hard water and WHO standard soft water should be published as WHO test methods (see Annex 2 in this report). 

A suspension of known concentration of deltamethrin in standard hard water is prepared by adding an entire water-dispersible tablet to standard hard water, poured into a 250-ml graduated cylinder, maintained at a constant temperature, and allowed to remain undisturbed for 30 minutes. The top nine-tenths are drawn off and the content of deltamethrin in the bottom one-tenth is determined, so allowing determination of the active ingredient mass still in suspension after 30 minutes. 

WHO standard hard water (WHO method WHO/M/29 see Annex 2, section II). 

The persistent foam at the top of 100ml of suspension prepared in WHO standard hard water (WHO method WHO/M/29 see Annex 2, section II) with 5ml of emulsion, oil in water, shall not exceed 10ml when tested by CIPAC method MT 47 (2). 

Fill the beaker with 1000 ml of standard hard water at 30°C + 2°C. The stirrer should be centrally located in the beaker and positioned in such a way that the lower edges of the stirrer blades are 60mm above the base of the beaker. The pitch of the stirrer blades and the direction of rotation are such that the propeller pushes the water upwards. Add the tablet to the water without stirring. Wait for 1 minute. Switch on the stirrer with the speed set to about 300 rev/min... 

Dilute one part of WHO standard hard water prepared as described in WHO method WHO/M/29, the hardness of which is 342mg/l, with nine parts of distilled water to give a hardness of 34.2 mg/1. 

The need for cell cultures for tests with viruses requires the incorporation of controls over and above those necessary for working with bacteria. In addition to cell culture controls to demonstrate lack of contamination and vims controls to demonstrate a functioning assay system, the level of input vims and the loss in virus infectivity upon the drying of the inoculum on the carrier need to be measured. In some cases, these measurements are only made once and the data used with a series of tests. However, it is recommended that, for proper accuracy, such measurements should be included with every test due to inherent variations in cell cultures and viruses. When there is a need to separate virus kill from simple mechanical removal of the test vims during the test, it is recommended that a control also be included to determine the mechanical removal of the test virus standard hard water should be used for this purpose in place of the test topical product. For any claim of topical antisepsis, reduction in the vims titer on treatment with the test product must be substantially higher than that obtained with the standard hard water treatment alone. 

One possible compromise here would be to develop an index based on the performance of a neutral agent that only mechanically removes viruses from hands. In the past, nonmedicated soaps have often been used for this purpose. However, soaps on the market differ widely, especially in properties such as pH and detergent action. Tap water also differs at different geographical locations. Therefore, a simple, safe, and readily available solution such as standard hard water (e.g., with 200 ppm hardness) could be used to establish the reference point for this index. Product efficacy claims could then be allowed at a certain differential above the mechanical virus removal with hard water. Manufacturers could publish the performance index of their formulation on the label to aid in product selection. To prevent minor differences in indices being used as a sales feature, a simple product classitication scheme could be developed. 

It all goes according to plan we expect to launch ABACUS Version 2 by the end of summer 1987. This would offer the integrated search system, structure display accompanying all appropriate functions on screen and structures optionally included on a range of standard hard copy outputs. Next we shall concentrate on developing Version 3, which will provide direct structure registration by the chemists, stock control... 

In the standardized hardness tests most often used today a hard indenter is pressed into the surface of the specimens under investigation, which is exactly in line with the historical definition of hardness given by Martens in 1908 that hardness is the resistance against indentation by a harder body. Hardness testing is comparatively simply, quickly and efficiently and is called nearly non-destructive. 

Standard hardness values for ceramic materials are listed in Table 63. 

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