Meter Convention

This lack of standards was resolved in the second half of the 19th centniy with the signatnre of the Meter Convention. This convention is a diplomatic treaty, which was signed in Paris (France) on 20 May 1875. This treaty establishes the International System of Units (SI) for the signatory countries. Currently 52 countries (all the major industrialized countries) have signed the treaty, and 36 countries are associate members. 

The main aims of the Meter Convention are to achieve international uniformity of measurements of all kinds, establish a common system of units, achieve equivalent measurement standards in the members states, harmonize laws and regulations relative to measurements in the member states and achieve mutual recognition of measurements. 

The quantity relevant to chemistry (i.e. the amount of substance) was adopted orrly in 1971, almost 100 years after the original signature of the meter convention. The urrit of the amount of substance in the SI system is the mole (mol). 

In the field of chemical measurements, part (1) is now underway in many countries. The basis for (2) has been laid for ah kinds of measurements by the General Conference of the Meter Convention and includes high-level interlaboratory comparisons (key comparisons) as an important element [2, 3], Metrology in chemistry is included in this comparison system through CCQM [4, 5], In the following these two parts are dealt with in more detail. 

While the establishment and implementation of national traceability systems is left to the countries and their legislation, the mutual recognition of these national systems calls for an international mechanism, at least if worldwide mutual recognition is aimed at. The MRA of the Meter Convention for national measurement standards and calibration and measurement certificates issued by NMIs [2] can be expected to at least provide for one important aspect of the task, namely the establishment of international equivalence at the national standards level. Together with the success of the work currently carried out by the International Laboratory Accreditation Cooperation (ILAC) for the harmonization of national laboratory accreditation schemes, the MRA will be the key to comparability and hence to ac-... 

The overall merits of producing and dealing with traceable results of measurement have clearly been acknowledged by the signatories of the Meter Convention whose primary raison-d etre is in fact traceability [3]. It is therefore a central question how this traceability of results is best achieved in chemical measurement. This has to be seen in the light of the two key elements that must be in place for producing traceable values ... 

The CIPM-MRA is a transparent process to underpin measurement capability claims of signatories to the meter convention. Key comparisons are organized for NMIs or designated laboratories to demonstrate the equivalence of their measurements in view of mutual acceptance of national standards and reference measurements. Their reported results and the equivalence statements of the measurements are included in the Appendix B of the CIPM-MRA, which can support the CMCs in Appendix C of the CIPM-MRA. Once reported there is no possibility of withdrawal of measurement results. Conversely, in a CCQM pilot study results could be withdrawn, but participation does not result in equivalence statements in Appendix B of the CIPM MRA. Therefore, participation in CCQM pilot studies was recently extended to invited expert laboratories. The results of both CCQM key comparisons and pilot studies are published in the Technical Supplement of Metrologia [24], The IRMM assists the CIPM to support the MRA by making... 

Not surprisingly, costs are several times higher than conventional wells. Nevertheless, overall project economics may favour ERD over other development options. For example, BP developed the offshore part of the Wytch Farm Oilfield (which is located under Poole Harbour in Dorset, UK) from an onshore location. The wells targeted the reservoir at a vertical depth of 1,500 meters with a lateral displacement of over 8,000 meters (Fig. 3.20). The alternative was to build a drilling location on an artificial island in Poole Bay. ERD probably saved a considerable amount of money and advanced first oil by several years. 

Origin. Typical meteorites have formation ages of 4.55 Gyr and exposure ages of only 10 years, duting which time they existed as meter-sized bodies unshielded to the effects of cosmic rays. With the exception of the SNC (Martian) and lunar meteorites it is widely befleved that most conventional... 

Because of the very large resistance of the glass membrane in a conventional pH electrode, an input amplifier of high impedance (usually 10 —10 Q) is required to avoid errors in the pH (or mV) readings. Most pH meters have field-effect transistor amplifiers that typically exhibit bias currents of only a pico-ampere (10 ampere), which, for an electrode resistance of 100 MQ, results in an emf error of only 0.1 mV (0.002 pH unit). 

Urethanes are processed as mbber-like elastomers, cast systems, or thermoplastic elastomers. The elastomer form is mixed and processed on conventional mbber mills and internal mixers, and can be compression, transfer, or injection molded. The Hquid prepolymers are cast using automatic metered casting machines, and the thermoplastic peUets are processed like aU thermoplastic materials on traditional plastic equipment. The unique property of the urethanes is ultrahigh abrasion resistance in moderately high Shore A (75—95) durometers. In addition, tear, tensUe, and resistance to many oUs is very high. The main deficiencies of the urethanes are their resistance to heat over 100°C and that shear and sliding abrasion tend to make the polymers soft and gummy. 

Media recovery magnetic dmms are conventionally available in 762 or 914 mm diameter and in dmm widths to 3.05 meters, usually in increments of 305 mm. The effective magnet width is about 150 mm less than the overall dmm width. In some instances 1219 mm dia wet magnetic dmms have been used, but the higher capacity of these units does not usually justify the higher costs involved. 

Conventional nitrocellulose lacquer finishing leads to the emission of large quantities of solvents into the atmosphere. An ingeneous approach to reducing VOC emissions is the use of supercritical carbon dioxide as a component of the solvent mixture (172). The critical temperature and pressure of CO2 are 31.3°C and 7.4 MPa (72.9 atm), respectively. Below that temperature and above that pressure, CO2 is a supercritical fluid. It has been found that under these conditions, the solvency properties of CO2 ate similar to aromatic hydrocarbons (see Supercritical fluids). The coating is shipped in a concentrated form, then metered with supercritical CO2 into a proportioning airless spray gun system in such a ratio as to reduce the viscosity to the level needed for proper atomization. VOC emission reductions of 50% or more are projected. 

The two principal elements of evaporator control are evaporation rate a.ndproduct concentration. Evaporation rate in single- and multiple-effect evaporators is usually achieved by steam-flow control. Conventional-control instrumentation is used (see Sec. 22), with the added precaution that pressure drop across meter and control valve, which reduces temperature difference available for heat transfer, not be excessive when maximum capacity is desired. Capacity control of thermocompression evaporators depends on the type of compressor positive-displacement compressors can utilize speed control or variations in operating pressure level. Centrifugal machines normally utihze adjustable inlet-guide vanes. Steam jets may have an adjustable spindle in the high-pressure orifice or be arranged as multiple jets that can individually be cut out of the system. 

Structures or pits for water lines are mostly of steel-reinforced concrete. At the wall entrance, contact can easily arise between the pipeline and the reinforcement. In the immediate vicinity of the pit, insufficient lowering of the potential occurs despite the cathodic protection of the pipeline. Figure 12-7 shows that voltage cones caused by equalizing currents are present up to a few meters from the shaft. With protection current densities of 5 mA mr for the concrete surfaces, even for a small pit of 150 m surface area, 0.75 A is necessary. A larger distribution pit of 500 m requires 2.5 A. Such large protection currents can only be obtained with additional impressed current anodes which are installed in the immediate vicinity of the pipe entry into the concrete. The local cathodic protection is a necessary completion of the conventional protection of the pipeline, which would otherwise be lacking in the pit. 

Flow itnbalance, double-flow centrifugals, 144 Flow measurement, 345 Flow meters, 431 Flow nozzle, 431 Flow terminology conventions, 21... 

The use of tracers for airflow measurement in ventilation ducts is not very common. There are several reasons for this. Compared to other flow measurement methods, tracers require more complicated equipment, skilled personnel, and are more expensive. There are, however, situations when conventional measurement methods are not applicable. For instance, if the space available is small, and hence the flow meter cannot be installed, or if no space is free to carry out traversing measurements, the use of a tracer might be an alternative. 

As the measuring distance for such equipment can be up to about. 50 m, this technique is advantageous in cases when conventional acoustic or vibro-meter devices are difficult or even impossible to use, such as high-frequency vibration measurements on the walls of high-level air ducts. 

---