Standardization hydroxide

Fig. 5.2.8 Size control of the basic aluminum sulfate particles by seeding in the standard system A-3 (B-3). The added amounts of the seeds in terms of the equivalent volume of the stock seed suspension in 24 cm3 of the standard hydroxide gel were (a) 0, (b) 1.2 X 10 2, (c) 2.4 X 10-1, and (d) 2.4 cm3. (From Ref. I.)...

In subsequent studies, a similar interaction between 2-aminonicotinal-dehyde and unsymmetrical functionalized alkan-2-ones was reported. This method typically provides substituted [l,8]naphthyridines in high yields under standard hydroxide-catalyzed conditions (OlOLllOl, 07MC25, 07RCB1911). 

The liberated iodine is titrated with standard sodium thiosulphate(Vr) solution after acidification to remove the hydroxide ions. 

The anhydrous chloride is prepared by standard methods. It is readily soluble in water to give a blue-green solution from which the blue hydrated salt CuClj. 2H2O can be crystallised here, two water molecules replace two of the planar chlorine ligands in the structure given above. Addition of dilute hydrochloric acid to copper(II) hydroxide or carbonate also gives a blue-green solution of the chloride CuClj but addition of concentrated hydrochloric acid (or any source of chloride ion) produces a yellow solution due to formation of chloro-copper(ll) complexes (see below). 

The molecular weight of many carboxylic acids which arc freely soluble in cold water (i.e., chiefly the aliphatic acids) can readily be obtained by titrating a known weight of the acids in aqueous solution with standard sodium or potassium hydroxide solution, using phenolphthalein as an indicator. To avoid the use of unduly large quantities of the acid, it is advisable to use Mj2 caustic alkali solution, and in order to obtain a sharp end>point, this alkali solution... 

The method is generally applicable when other modes of esterification are either slow, inefficient, or likely to cause isomerisation it is, however, time-consuming and expensive. Small quantities of acid impurities are sometimes produced, hence it is advisable to wash the ester with saturated sodium bicarbonate solution. The silver salt can usually be prepared by dissolving the acid in the calculated quantity of standard ammonium hydroxide solution and... 

It is essential to standardise the alcoholic potassium hydroxide solution immediately before use by titration with standard 0-5N or 0-25N hydrochloric or sulphuric acid using phenolphthalein as indicator. 

Now the easy part -isolating your product. One of the most attractive features of this new synthesis is that the standard Ai/(Hg) amination mixture must be tediously filtered to separate the product from the spent aluminum hydroxide sludge at this point. The following remedies this most frustrating step and will probably give many a new outlook on the potential of the AI(Hg) reduction. 

For the secondary pH reference standards, the buffer value is 0.070 for potassium tetroxalate and 0.09 for calcium hydroxide. 

To prepare the standard pH buffer solutions recommended by the National Bureau of Standards (U.S.), the indicated weights of the pure materials in Table 8.15 should be dissolved in water of specific conductivity not greater than 5 micromhos. The tartrate, phthalate, and phosphates can be dried for 2 h at 100°C before use. Potassium tetroxalate and calcium hydroxide need not be dried. Fresh-looking crystals of borax should be used. Before use, excess solid potassium hydrogen tartrate and calcium hydroxide must be removed. Buffer solutions pH 6 or above should be stored in plastic containers and should be protected from carbon doxide with soda-lime traps. The solutions should be replaced within 2 to 3 weeks, or sooner if formation of mold is noticed. A crystal of thymol may be added as a preservative. 

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

The most common strong base for titrating acidic analytes in aqueous solutions is NaOH. Sodium hydroxide is available both as a solid and as an approximately 50% w/v solution. Solutions of NaOH may be standardized against any of the primary weak acid standards listed in Table 9.7. The standardization of NaOH, however, is complicated by potential contamination from the following reaction between CO2 and OH . 

Standards for dmg chemicals are pubUshed ia USP—NE. Dmg substances are chemicals that have therapeutic or diagnostic uses, whereas pharmaceutical iagredients provide preservative action, fiavoiing, or hilfillment of a function ia the formulation of dosage-form dmgs. Examples of dmg substances are acetaminophen [103-90-2] ampicillin [69-53-4] aspirin [50-78-2] powdered ipecac, riboflavin [83-88-5] staimous fluoride [7783-47-3] and thyroid. Examples of pharmaceutical iagredients are ethylparaben [120-47-8] lactose [63-42-3] magnesium stearate [557-04-0] sodium hydroxide [1310-73-2] starch [9005-25-8] and vanillin [121-33-5],... 

In 1973 the Semiconductor Equipment and Materials Institute (SEMI) held its first standards meeting. SEMI standards are voluntary consensus specifications developed by the producers, users, and general interest groups in the semiconductor (qv) industry. Examples of electronic chemicals are glacial acetic acid [64-19-7] acetone [67-64-17, ammonium fluoride [12125-01 -8] and ammonium hydroxide [1336-21 -6] (see Ammonium compounds), dichloromethane [75-09-2] (see Cm.OROCARBONSANDcm.OROHYDROCARBONs), hydrofluoric acid [7664-39-3] (see Eluorine compounds, inorganic), 30% hydrogen peroxide (qv) [7722-84-1] methanol (qv) [67-56-1] nitric acid (qv) [7697-37-2] 2-propanoI [67-63-0] (see Propyl alcohols), sulfuric acid [7664-93-9] tetrachloroethane [127-18-4] toluene (qv) [108-88-3] and xylenes (qv) (see also Electronic materials). 

Procedures for determining the quaUty of formaldehyde solutions ate outlined by ASTM (120). Analytical methods relevant to Table 5 foUow formaldehyde by the sodium sulfite method (D2194) methanol by specific gravity (D2380) acidity as formic acid by titration with sodium hydroxide (D2379) iron by colorimetry (D2087) and color (APHA) by comparison to platinum—cobalt color standards (D1209). 

The concentration of aqueous solutions of the acid can be deterrnined by titration with sodium hydroxide, and the concentration of formate ion by oxidation with permanganate and back titration. Volatile impurities can be estimated by gas—Hquid chromatography. Standard analytical methods are detailed in References 37 and 38. 

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

Oxidation. The oxidation reactions of organoboranes have been reviewed (5,7,215). Hydroboration—oxidation is an anti-Markovnikov cis-hydration of carbon—carbon multiple bonds. The standard oxidation procedure employs 30% hydrogen peroxide and 3 M sodium hydroxide. The reaction proceeds with retention of configuration (216). 

The fermentation-derived food-grade product is sold in 50, 80, and 88% concentrations the other grades are available in 50 and 88% concentrations. The food-grade product meets the Vood Chemicals Codex III and the pharmaceutical grade meets the FCC and the United States Pharmacopoeia XK specifications (7). Other lactic acid derivatives such as salts and esters are also available in weU-estabhshed product specifications. Standard analytical methods such as titration and Hquid chromatography can be used to determine lactic acid, and other gravimetric and specific tests are used to detect impurities for the product specifications. A standard titration method neutralizes the acid with sodium hydroxide and then back-titrates the acid. An older standard quantitative method for determination of lactic acid was based on oxidation by potassium permanganate to acetaldehyde, which is absorbed in sodium bisulfite and titrated iodometricaHy. 

Functional Group Analysis. The total hydroxyl content of lignin is determined by acetylation with an acetic anhydride—pyridine reagent followed by saponification of the acetate, and followed by titration of the resulting acetic acid with a standard 0.05 W sodium hydroxide solution. Either the Kuhn-Roth (35) or the modified Bethge-Liadstrom (36) procedure may be used to determine the total hydroxyl content. The aUphatic hydroxyl content is determined by the difference between the total and phenoHc hydroxyl contents. 

The method of choice for determining carboxyl groups in lignin is based on potentiometric titration in the presence of an internal standard, /)-hydroxybenzoic acid, using tetra- -butylammonium hydroxide as a titrant (42). The carboxyl contents of different lignins are shown in Table 6. In general, the carboxyl content of lignin increases upon oxidation. 

AH gg = —43.03 kJ/mol ( — 10.28 kcal/mol) including heat of solution, at standard state m = V) and may require a heat sink to prevent boiling of the reaction mixture. A 30% by weight suspension of MgO in 20°C water boils in the absence of any heat sink. The time to reach boiling is dependent on the reactivity of the MgO raw material, and this time can be only several hours for the more reactive grades of MgO. Investigations of the kinetics of formation of magnesium hydroxide by hydration of MgO have been reported (79). 

Unsaturation value can be determined by the reaction of the akyl or propenyl end group with mercuric acetate ia a methanolic solution to give acetoxymercuric methoxy compounds and acetic acid (ASTM D4671-87). The amount of acetic acid released ia this equimolar reaction is determined by titration with standard alcohoHc potassium hydroxide. Sodium bromide is normally added to convert the iasoluble mercuric oxide (a titration iaterference) to mercuric bromide. The value is usually expressed as meg KOH/g polyol which can be converted to OH No. units usiag multiplication by 56.1 or to percentage of vinyl usiag multiplication by 2.7. 

Commercial Hquid sodium alumiaates are normally analyzed for total alumiaa and for sodium oxide by titration with ethylene diaminetetraacetic acid [60-00-4] (EDTA) or hydrochloric acid. Further analysis iacludes the determiaation of soluble alumiaa, soluble siHca, total iasoluble material, sodium oxide content, and carbon dioxide. Aluminum and sodium can also be determiaed by emission spectroscopy. The total iasoluble material is determiaed by weighing the ignited residue after extraction of the soluble material with sodium hydroxide. The sodium oxide content is determiaed ia a flame photometer by comparison to proper standards. Carbon dioxide is usually determiaed by the amount evolved, as ia the Underwood method. 

A number of simple, standard methods have been developed for the analysis of ammonium compounds, several of which have been adapted to automated or instmmental methods. Ammonium content is most easily deterrnined by adding excess sodium hydroxide to a solution of the salt. Liberated ammonia is then distilled into standard sulfuric acid and the excess acid titrated. Other methods include colorimetry (2) and the use of a specific ion electrode (3). 

Ammonium acetate solutions formed by neutralizing acetic acid using ammonium hydroxide are essentially neutral. Thus, these solutions are suitable for standardization of electrodes, and for use as titration standards. Solutions must be used while fresh, however, as they become acidic on standing. 

Occupational Safety and Health. OSHA has set no specific limits for sodium and potassium sibcates (88). A pmdent industrial exposure standard could range from the permissible exposure limit (PEL) for inert or nuisance particulates to the PEL for sodium hydroxide, depending on the rate of dissolution and the concentration of airborne material. Material safety data sheets issued by siUcate producers should be consulted for specific handling precautions, recommended personal protective equipment, and other important safety information. 

Analytical Methods. A classical and stiU widely employed analytical method is iodimetric titration. This is suitable for determination of sodium sulfite, for example, in boiler water. Standard potassium iodate—potassium iodide solution is commonly used as the titrant with a starch or starch-substitute indicator. Sodium bisulfite occurring as an impurity in sodium sulfite can be determined by addition of hydrogen peroxide to oxidize the bisulfite to bisulfate, followed by titration with standard sodium hydroxide (279). 

---