Paraformaldehyde 40 percent

Bischloromethyl ether has been prepared by saturation of formalin with dry hydrogen chloride by the reaction of paraformaldehyde with phosphorus trichloride or phosphorus oxychloride, by solution of paraformaldehyde in concentrated sulfuric acid and treatment with ammonium chloride or dry hydrogen chloride, and by suspension of paraformaldehyde in seventy or eighty percent sulfuric acid and treatment with chlorosulfonic acid. It is formed together with the asymmetrical isomer when methyl ether is chlorinated and when paraformaldehyde is treated with chlorosulfonic acid. The present method has been published. ... 

The wax used contained 50 percent solids and the source of formaldehyde was powdered paraformaldehyde. 

Weighed amounts of prepared wood particles were tumbled in a laboratory blender and a wax emulsion (1 percent solids oven-dry basis) was added from a spray gun, after which concentrated bark extract (8 percent solids oven-dry basis) was sprayed onto the tumbling mixture. Powdered paraformaldehyde (1 percent oven-dry basis) was added slowly to the stirred mixture. 

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. 

It also can be produced directly from natural gas, methane, and other aliphatic hydrocarbons, but this process yields mixtures of various oxygenated materials. Because both gaseous and liquid formaldehyde readily polymerize at room temperature, formaldehyde is not available in pure form. It is sold instead as a 37 percent solution in water, or in the polymeric form as paraformaldehyde [HO(CH20)nH], where n is between 8 and 50, or as trioxane (CH20)3. The greatest end use for formaldehyde is in the field of synthetic resins, either as a homopolymer or as a copolymer with phenol, urea, or melamine. It also is reacted with acetaldehyde to produce pentaerythritol [C(CH2OH)4], which finds use in polyester resins. Two smaller-volume uses are in urea-formaldehyde fertilizers and in hexamethylenetetramine, the latter being formed by condensation with ammonia. 

Novolaks were prepared using a phenol-to-formaldehyde molar ratio of 4 1 with 5 mole percent of H2SO4 added as a catalyst. Typically, 47 g liquid phenol (91.7% assay), 3 g paraformaldehyde, and 30 mL water plus the required acid catalyst were added to a three-neck, 250-mL round bottom flask. The flask was fitted with a reflux condenser and stirrer. The mixture was refluxed for 2 to 4 hours with the oil bath at 115 °C then, the mixture was neutralized with 50% (w/w) NaOH and the excess phenol removed by steam distillation for 5 to 6 hours. The remaining viscous oily residue was washed repeatedly with boiling water. A novolak with the P/N fraction was prepared as described above with 1 1 by volume phenol and P/N fraction and half of the amount of formaldehyde. Initial wood-gluing testing with this novolak indicates wood failure rather than glueline failure. 

As a source of HCHO, formalin, a 37 percent aqueous solution of HCHO stabilized with 12 to 15 percent of methanol, is the most popular. Besides formalin, paraformaldehyde [(HCHO) ] and trioxane [(HCHO)3] are also used. When methanol is added in the feed or when methylal [CH2(OCH3)2] or hemiformal [CH3OCH2 OH] is used as the source of HCHO, a mixture of carboxylic acids and esters is obtained because both the esterification of carboxylic acid and the hydrolysis of ester are much more rapid than the condensation reaction. The reaction is usually performed in the presence of an excess of carboxylic acid with respect to the amount of HCHO the carboxylic acid/HCHO molar ratio is 1.3 to 20 because HCHO is generally more susceptible to degradation than carboxylic acids. The reaction temperature is in the range of 250 to 400 °C. 

The best overall performance is obtained by mixing 9 to 10 weight percent l,3,5,7-tetraazatricyclo[3.3.3.P ]decane into a novolac that is prepared using a ratio of phenol to paraformaldehyde of 1 0.8. Equations 18 to 21 show a... 

Table 2. Unreacted formaldehyde (as percent of original amount) for different times and temperatures of reaction between paraformaldehyde and pine bark extracts of various treatments.

Formaldehyde for use as a disinfectant is usually marketed as formalin, a solution of about 37 percent concentration, or as paraformaldehyde, a solid polymerized compound. The substance can be utilized for decontamination of large areas (427) or surfaces (451). Formaldehyde in a concentration of 5 percent active ingredient is an effective liquid disinfectant. Formaldehyde at 0.2 to 4.7 percent is often used to inactivate viruses in the preparation of vaccines. Formaldehyde seems to be more effective as a disinfectant against hydrophilic viruses than against lipophilic viruses. Forty percent aqueous formalin (16 percent formaldehyde) is effective in inactivating hepatitis B virus, using a contact time of 12 hours. A 20 percent formalin solution in 70 percent... 

Measure the cabinet and calculate its total internal volume. Calculate the amount of paraformaldehyde needed by multiplying the cabinet volume, in cubic meters, by 10 grams per cubic meter. This will yield a concentration of formaldehyde gas of 0.8 percent by weight or 10,000 parts per million by volume in air. 

Ammonium bicarbonate can be used to inactivate formaldehyde gas after decontamination is completed. If this is to be done, an additional hot plate with a large pyrex dish having a 1- to 2-inch-high wall is placed inside the cabinet Weigh a 10 percent excess of ammonium bicarbonate (compared to paraformaldehyde) into the dish and set the thermostat to 450°C (the temperature is critical). 

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