Solutions, formaldehyde Specifications

Specifications and Analytical Methods. The commercial aqueous solution is specified as 34% minimum butynediol, as determined by bromination or refractive index. Propargyl alcohol is limited to 0.2% and formaldehyde to 0.7%. 

Formaldehyde is sold in aqueous solutions with concentrations ranging from 25 to 56 wt % HCHO. Product specifications for typical grades (18,117—119)... 

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). 

Formaldehyde—Alcohol Solutions. These solutions are blends of concentrated aqueous formaldehyde, the alcohol, and the hemiacetal. Methanol decreases the average molecular weight of formaldehyde oligomers by formation of lower molecular weight hemiacetals. These solutions are used to produce urea and melamine resins the alcohol can act as the resin solvent and as a reactant. The low water content can improve reactivity and reduce waste disposal and losses. Typical specifications for commercially available products are shown in Table 7 (117). 

Table 7. Specifications and Physical Properties of Formaldehyde—Alcohol Solutions...

Nippon Shokubai and U.K. Seung are producing a fluorescent polymer claimed to be made from a co-condensation of ben2oguanamine and formaldehyde. Fine highly thermoset particles are manufactured in solution and later dried. It is useful in a wide range of appHcations, specifically plastics, and markets where bleed is a problem. 

Resoles. Like the novolak processes, a typical resole process consists of reaction, dehydration, and finishing. Phenol and formaldehyde solution are added all at once to the reactor at a molar ratio of formaldehyde to phenol of 1.2—3.0 1. Catalyst is added and the pH is checked and adjusted if necessary. The catalyst concentration can range from 1—5% for NaOH, 3—6% for Ba(OH)2, and 6—12% for hexa. A reaction temperature of 80—95°C is used with vacuum-reflux control. The high concentration of water and lower enthalpy compared to novolaks allows better exotherm control. In the reaction phase, the temperature is held at 80—90°C and vacuum-refluxing lasts from 1—3 h as determined in the development phase. SoHd resins and certain hquid resins are dehydrated as quickly as possible to prevent overreacting or gelation. The end point is found by manual determination of a specific hot-plate gel time, which decreases as the polymerization advances. Automation includes on-line viscosity measurement, gc, and gpc. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

The melting point of pentaerythritol corresponding with the above mentioned specification lies within 250 and 260°C (pure pentaerythritol melts at 261-262°Q. To produce it an aqueous solution of acetaldehyde is treated with formaldehyde in the presence of milk of lime, the temperature being gradually increased from 15 to 55°C. When the reaction is complete, the whole is treated with sulphuric acid sufficient to precipitate the lime as calcium sulphate. This is filtered off, and the solution concentrated under reduced pressure. The crystallized product is centrifuged and then recrystallized from water. The yield is about 62% (calculated with respect to acetaldehyde) or 51% if related to formaldehyde. 

This ester, known as methyl ether nitronitrate (more correctly as nitromethoxymethanol nitrate), is a colourless, oily liquid, boiling at 48°C at 15 mm Hg with a specific gravity 1.50 at 20°C. It readily dissolves collodion cotton, and is more volatile than nitroglycol. It was first produced by Moreschi [84] by nitrating jyw-dichlordimethyl ether formed by reacting a 40% formaldehyde solution with... 

Paraformaldehyde is made by dehydrating common formaldehyde solution. Use caution because it is a known carcinogen. This method produces what is known as Type B RDX, which contains 8 to 12 percent HMX. Since HMX is slightly more powerful than RDX and has other useful explosive characteristics, no one gets too concerned about this "impurity." HMX is specifically mentioned in the government specifications for C-4. 

The earliest detectors of S02 in the atmosphere were automated calorimetric wet chemical devices. The reference technique for determining the SOz content of atmospheric air is based on the absorption of S02 from an air sample by a solution of sodium tetrachloromercurate, which, upon the addition of formaldehyde and a pararosaniline dye, forms a strong purple dye complex. Several manufacturers have automated this procedure. Properly maintained, these units provide an excellent record of S02 concentration in the air, because they operate on the basis of a chemical reaction that is specific for S02. 

Exposure to chromium(VI) can result in DNA-protein complexes, the identification of which may be useful as biomarkers of exposure to chromates (Costa 1991). Gel electrophoresis and immunochemical techniques were used to identify actin as the protein in a DNA-protein complex induced by potassium chromate in cultured Chinese hamster ovary cells. While the DNA-protein complexes induced by formaldehyde and ultraviolet light were different from those induced by chromate, actin was also identified as the protein in the complex induced by cis-platinum, indicating that the DNA-actin complex is not specific for chromium. However, an experiment in a group of four volunteers did not demonstrate an increase in DNA-protein crosslinks in leukocytes over a 240 minute period following the ingestion of 5 mg chromium(VI) as potassium dichromate in a 10 mg chromium/L solution or the same amount added to 300 mL of orange juice (presumably reducing chromium(VI) to chromium(III)) and diluted to 500 mL with deionized water (Kuykendall et al. 1996). Chromium levels in red cells, plasma and urine were increased. In a separate experiment in this study, a threshold dose of 52 pg chromium(VI)/L was determined for crosslink formation in cultured lymphoma cells. 

Electroless plating — An autocatalytic process of metal deposition on a substrate by reduction of metal ions from solution without using an external source of electrons. It is promoted by specific reductants, namely formaldehyde, sodium hypophosphide, sodium boro-hydride, dialkylamine borane, and hydrazine. Electroless deposition has been used to produce different metal (e.g., nickel, cobalt, copper, gold, platinum, palladium, silver) and alloy coatings. It can be applied to any type of substrate including non-conductors. Some substrates are intrinsic catalytic for the electroless deposition other can be catalyzed usually by sensibilization followed by Pd nucleation also, in some non-catalytic metallic substrates the electroless process can be induced by an initial application of an appropriate potential pulse. In practical terms, the evaluation of the catalytic activity of a substrate for the electroless deposition of a given metal is... 

These assays resemble a hybrid of an immunohistochemistry assay and ELISA. Whole cells are fixed, for example with 3.7% formaldehyde, to MTPs permeabilized by repetitive washing with 0.1% Triton X-100, blocked with a protein solution, probed with primary antibodies (phospho-spe-cific, and non-phospho-specific), washed, and subsequently the secondary antibodies labeled with infrared fluorescent tags are added. After washing, these assays are read in a reader (such as the Odyssey or Aerius) designed for high sensitivity detection of two colors. The two colors are useful because one color can be used to accommodate a stain assigned as a total protein or cell number control or as an antibody to total protein, which allows for normalization. These assays may only require a single antibody versus the dual antibody sandwich required for ELISA. 

Product specification. All formaldehyde will be sold as N.F. solution containing 37.0 wt % formaldehyde and 8 wt % methanol. All sales may be considered to be by tank car. 

A widely used biocide and preservation product is formaldehyde. Solutions of formaldehyde in water, called formalin, were used for disinfection and conservation, for example, of biological samples for display. Bound formaldehyde is released in small amounts from common easy-care and durable press finishes (Chapter 5). Therefore these finishes include - at least until they are washed - a small antimicrobial side effect. This can also be true for some quaternary compounds, for example wet fastness improvers and softeners. But for more effective requirements specific antimicrobial finishes are necessary. 

I. Since commercial solutions of formaldehyde contain methyl alcohol, it is grossly inaccurate to estimate the amount of formaldehyde present by reference to specific gravity tables (. Org. 83m. 14, 92). The formaldehyde content of the solution is determined by analysis, for which the iodimetric method of Borgstrom and Horsch is recommended. The yield is calculated upon the basis of the amoimt of formaldehyde actually present, as shown by analysis. 

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