Twenty-five years of international collaboration in reference materials via ISO/REMCO

This paper looks back on a quarter century of history of the Council Committee on Reference Materials of the International Organization for Standardization – REMCO. It begins however with the period before its formation in 1976 to describe how the Committee came into being as a response to a growing need by the analytical community for the number and variety of reference materials (RMs) as well as a need for the assurance of the quality of RMs and ends with a view of REMCO activities in the near future. This is not intended as a detailed history but instead to describe the evolution of REMCO by identifying major activities and accomplishments of REMCO. Received: 21 January 2002 Accepted: 22 January 2002     

Effect of EDTA/NaF solutions on the orion Cu(II) ion-selective electrode

The titration of ethylenediaminetetra-acetic acid in fluoride medium with Cu(II) solution with the Orion Cu(II) ion-selective electrode as indicator, results (after several titrations) in a broad end-point which is unsatisfactory for exact analytical purposes. This effect has been found to arise from an enhanced rate of response to changes in EDTA concentration when the electrode has been exposed to an EDTA/NaF medium for prolonged periods.     

Determination of tin as stannite-kesterite and cassiterite in ores

Tin is stannite-kesterite and as cassiterite in a tin-bearing ore can be determined by the selective decomposition of the stannite-kesterite phase with a mixture of sodium nitrate and acetic acid.     

Flux vector splitting of the inviscid gasdynamic equations with application to finite-difference methods

The conservation-law form of the inviscid gasdynamic equations has the remarkable property that the nonlinear flux vectors are homogeneous functions of degree one. This property readily permits the splitting of flux vectors into subvectors by similarity transformations so that each subvector has associated with it a specified eigenvalue spectrum. As a consequence of flux vector splitting, new explicit and implicit dissipative finite-difference schemes are developed for first-order hyperbolic systems of equations. Appropriate one-sided spatial differences for each split flux vector are used throughout the computational field even if the flow is locally subsonic. The results of some preliminary numerical computations are included.     

The association in mixtures of dimethylsulphoxide and water as studied by Raman spectroscopy

In mixtures of dimethylsulphoxide (DMSO) and water, formation of a complex (DMSO) · (H₂O)₂ is indicated by wavenumber shifts and linewidth variations of the v SO Raman band. Higher temperatures interfere with this complex formation.     

The drying of sulphide-bearing materials in a microwave oven: A caveat

The drying of sulphide-bearing materials in a microwave oven should be undertaken with caution. Several sulphide minerals and sulphide-bearing materials have shown a susceptibility to oxidation (which may even be violent) during microwave drying and this could affect the results of subsequent work on these materials.     

Preparation and properties of the system CoPxS2−x

Lattice parameters were determined for members of the system CoP_xS_2?x (0 ≤ x ≥ 1). A cubic region was observed for 0 ≤ x ≤ 0·5 and a tetragonal region for 0·5 < x ≤ 1. Magnetization and susceptibility measurements were made on the sample CoP_xS_2?x (0 ≤ x ≤ 0·5) from 4·2 to 500°K and to 9·5 kOe. The ferromagnetic Curie temperature decreased almost linearly with composition from a value of 122(1)°K for x = 0 to 23(1)°K at x = 0·3. The saturation magnetization passed through a maximum at 41·5(2) e.m.u./g at x = 0·05, increasing from 40·0(2) e.m.u./g for x = 0, and then decreased to below 15 e.m.u./g for x = 0·3. The paramagnetic data gave a P²_eff/CO²⁺ that increased linearly with phosphorus substitution from 4·4(2)μ_B at x = 0 to 5·5(2)μ_B² at x = 0·5. The Weiss constant decreased almost linearly from 150(3)°K for x = 0 to 85(2)°K for x = 0·3. The magnetic properties of this system are compared with those of the system CoAs_xS_2?x and CoSe_xS_2?x. Changes, with composition, in the Curie and Weiss temperatures are almost identical in the three systems for x ≤ 0·25. As with CoAs_xS_2?x the ferromagnetic moment reaches a maximum at x = 0·05 and then decreases with increasing x, although the magnetic interactions remain ferromagnetic for all x ≤ 0·5.     

Oxidation of sulphide minerals--II: determination of metal in the oxidation products of galena, sphalerite and chalcocite

A 15% ammonium acetate and 3% acetic acid solution has been shown to be useful in the determination of the principal metal in small amounts of the oxidation products of galena, sphalerite and chalcocite. Its use in the determination of the extent of oxidation in concentrates or complex ores of these minerals is implied.     

Optical detection and ionization of donors in specific electronic and nuclear spin States

We resolve the remarkably sharp bound exciton transitions of highly enriched 28Si using a single-frequency laser and photoluminescence excitation spectroscopy, as well as photocurrent spectroscopy. Well-resolved doublets in the spectrum of the 31P donor reflect the hyperfine coupling of the electronic and nuclear donor spins. The optical detection of the nuclear spin state, and selective pumping and ionization of donors in specific electronic and nuclear spin states, suggests a number of new possibilities which could be useful for the realization of silicon-based quantum computers.     

Littlewood–Paley Theory for Triangle Buildings

For the natural two-parameter filtration \(\left( {\mathcal {F}_\lambda }: {\lambda \in P}\right) \) on the boundary of a triangle building, we define a maximal function and a square function and show their boundedness on \(L^p(\Omega _0)\) for \(p \in (1, \infty )\). At the end, we consider \(L^p(\Omega _0)\) boundedness of martingale transforms. If the building is of \({\text {GL}}(3, \mathbb {Q}_p)\), then \(\Omega _0\) can be identified with p-adic Heisenberg group.