Mixing endpoint

An analytical solution for molecules with alkaline functionality is acid/base titration. In this technique, the polymer is dissolved, but not precipitated prior to analysis. In this way, the additive, even if polymer-bound, is still in solution and titratable. This principle has also been applied for the determination of 0.01 % stearic acid and sodium stearate in SBR solutions. The polymer was diluted with toluene/absolute ethanol mixed solvent and stearic acid was determined by titration with 0.1 M ethanolic NaOH solution to the m-cresol purple endpoint similarly, sodium stearate was titrated with 0.05 M ethanolic HC1 solution [83]. Also long-chain acid lubricants (e.g. stearic acid) in acrylic polyesters were quantitatively determined by titration of the extract. 

Rizk et al. [3] used 2,3-dichloro-5,6-dcyano-/)-benzoquinone as a redox titrant in the aqueous titration of penicillamine. Finely ground tablets were mixed with H20 and the mixture was filtered. The filtrate (or an injectable solution) was diluted with H20 and acidified with H3PO4 before titration with the redox titrant. The titration was conducted in anhydrous acetic acid using thiethylperazine dihydrochloride as the indicator. The endpoint was detected by a color change to green, and recoveries of penicillamine were 98.4-100.5%. 

Ammoniacal ethanol is prepared by chilling ten liters of anhydrous denatured ethyl alcohol as commercially purchased in a freezer to well below 0° C. Next, 600 to 750 ml of liquid ammonia is drawn from a pressure cylinder into a 1000 ml graduate in a well ventilated area. The contents of the graduate are carefully poured into the chilled alcohol. The solution is then stirred to mix and warmed to room temperature. The solution should be at least two molar as determined by titration against standard acid solution to a methyl red endpoint. If titration is to be attempted, a little methyl red should be added to the chemical list. 

Molenberghs G, Geys H, Buyse M. Evaluation of surrogate endpoints in randomized experiments with mixed discrete and continuous outcomes. Stat Med 2001 20 3023-38. 

The method of Koval chuk et al. was applied in the determination of procaine [84], These authors have also developed another alkalimetric two-phase titration method for determination of the salts of organic bases, including procaine hydrochloride [85]. A solution of the base salt was mixed with 2 mL chloroform and 2 drops of 0.15% methylene blue solution, and the mixture titrated with 0.02 to 0.1 M sodium hydroxide with shaking. At the endpoint, the chloroform layer becomes pink-violet. 

There is also the possibility of mixing hierarchical considerations with adjustment. For example, in the case of a single primary endpoint and two secondary endpoints, of equal importance to each other, the primary endpoint would be evaluated at a = 0.05 while each of the secondary endpoints would use a = 0.025. Claims could only be considered for the secondary endpoints if the primary endpoint gave p < 0.05, but then additional claims could be made on whichever of the secondary endpoints gives p < 0.025. In theory the use of both a hierarchy and Bonferroni-type adjustments could move beyond a second level, all that is needed is that 0.05 is assigned to each level of the hierarchy. For example, there could be a single endpoint at the first level, two endpoints at the second level (with a Bonferroni adjustment) and finally a single endpoint at the third level. 

The iron oxides, especially the magnetite and hematite ores, are primary sources of industrial iron these ores cross mixed-valence states in the blast-furnace or any other reduction process - before reaching the metallic endpoint. 

If two compositions on the composition triangle are mixed, the resulting composition lies on a line joining them. In this case the starting compositions lie at the endpoint of a binary tie-line and the mixture composition can be located using the lever principle. 

Acidity. Mix 100ml of sample with 100ml of freshly-boiled distd w (free of C02), add 2 drops of bromothymol blue indicator (0,04% LaMotte or Taylor solns) and titrate with 0.01N Na hydroxide soln to a blue endpoint. Calculate the acidity as acetic acid as follows ... 

A colorimetric method based on the violet color produced by ferrous sulfate in sulfuric acid in the presence of N03 was announced by English in 1947 (Ref 9) and applied to the determination of NA and nltrosylsulfuric acid (NSA) in spent mixed acid. Since then a number of papers (Refs 13, 14, 15, 16 and 17) have extended the method to NOa, organic nitrates and RDX -HMX mixtures Analytical Methods The visual determination of the endpoint (appearance of a permanent brown color) in the dead-stop titrimetric method is reported accurate to 0.03ml (Ref 3) and was used recently by Frejacques and LeClercq (Ref 12) for analysis of Pentolites, Tetryls, NGu, NG prepns, and Nitroethane-EGDN expls. The endpoint has been criticized as difficult to see, and if problems arise, electrometric methods are available for detection (Refs 6,... 

This method can be used for the determination of the ozone concentration in the gas and/or liquid phase. The measurement takes place in the liquid phase, though, so that to measure a process gas containing ozone, the gas must first be bubbled through a flask containing potassium iodide KI. For the measurement of the liquid ozone concentration, a water sample is mixed with a KI solution. The iodide F is oxidized by ozone. The reaction product iodine 12 is titrated immediately with sodium thiosulfate Na2S203 to a pale yellow color. With a starch indicator the endpoint of titration can be intensified (deep blue). The ozone concentration can be calculated by the consumption of Na2S203. 

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