Methylene, determination 212 INDEX

Metameric Colours. Colours that appear to be the same under one type of illuminant but, because they have different spectral reflectivity curves, will not match under a different illuminant. Two white vitreous enamels may be metameric, for example, if one is opacified with titania in the anatase form whereas the other contains titania in the form of rutile. Methuselah. A 9-quart wine bottle. Methylene Blue Index A simple approximate method for assessing the surface area of a clay. O.OIM methylene blue dye is added to aqueous suspension of clay, in successive small amounts, to determine the least amount of dye required to impart colour to the water suspending the clay. Dye up to this amount is absorbed by the clay, so that this is a measure of the clay s cation exchange capacity (see ionic exchange). For most pottery clays this is proportional to the surface area to a good approximation. ASTM C837 specifies a test for clays. 

International Organization for Standardization, Water Quality—determination of surfactants— Part 1 Determination of anionic surfactants by measurement of the methylene blue index (MBAS), ISO 7875/1 1984. Geneva, Switzerland. 

Methylene iodide [75-11-6], CH2I2, also known as diio dome thane, mol wt 267.87, 94.76% I, mp 6.0°C, and bp 181°C, is a very heavy colorless Hquid. It has a density of 3.325 g/mL at 20°C and a refractive index of 1.7538 at 4°C. It darkens in contact with air, moisture, and light. Its solubiHty in water is 1.42 g/100 g H2O at 20°C it is soluble in alcohol, chloroform, ben2ene, and ether. Methylene iodide is prepared by reaction of sodium arsenite and iodoform with sodium hydroxide reaction of iodine, sodium ethoxide, and hydroiodic acid on iodoform the oxidation of iodoacetic acid with potassium persulfate and by reaction of potassium iodide and methylene chloride (124,125). Diiodoform is used for determining the density and refractive index of minerals. It is also used as a starting material in the manufacture of x-ray contrast media and other synthetic pharmaceuticals (qv). 

The assumption of different degrees of order between polymers having odd or even numbers of methylene units in die spacer is verified by the X-ray diffraction patterns shown in Figure 7. Crystallinity index data were determined on the basis of these diffraction patterns and the data are presented in Table I. The crystallinity index was calculated according to Equation 1, in which Ac is the area of the sharp Bragg reflections corresponding to the crystalline part of the polymer, and Aa is the area of the broad amorphous peak. 

The standard compounds will all be available as solutions of 1 g of each dissolved in 20 mL of a 50 50 mixture of methylene chloride and ethanol. The purpose of the first reference plate is to determine the order of elution (R values) of the known substances and to index the standard reference mixture. Several of the substances have similar Revalues, but you will note a different behavior for each spot with the visualization methods. On the sample plate, the standard reference mixture will be spotted, along with Naproxen sodium and several solutions that you will prepare from commercial analgesic tablets. These tablets will each be crushed and dissolved in a 50 50 methylene chloride-ethanol mixture for spotting. 

The retention index is calculated by logarithmic interpolation between consecutive alkanes and the data acquired under isothermal analysis conditions. Under linear temperature programming, however, an almost identical system of expressing retention data is the methylene unit concept in which methylene unit (MU) values are determined by linear interpolation between the /i-alkanes eluted before and after the compound (Dalgliesh etal, 1966). For example, a peak eluted midway between C19 and C20 under these conditions would have a MU value of 19.50 and an equivalent retention index calculated from this of approximately 1950. The interrelation of isothermal and temperature-programmed data for a particular type of phase, even under widely different analytical conditions, is possible and both concepts permit very useful comparisons of different sets of available literature data. Relative retention times, on the other hand, can show fairly wide variations in values, especially with regard to temperature, and are less suited for use as literature reference data. 

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