Solutions, formaldehyde Purity

Fomialdehyde [50-00-0] H2C=0, is the first of the series of aUphatic aldehydes. It was discovered by Buderov ia 1859 and has been manufactured siace the beginning of the twentieth century. Annual woddwide production capacity now exceeds 15 x 10 t (calculated as 37% solution). Because of its relatively low cost, high purity, and variety of chemical reactions, formaldehyde has become one of the wodd s most important iadustrial and research chemicals (1). 

Formaldehyde is a gas with a boiling point of -21 °C. It is usually supplied as a stabilised aqueous solution ( 40% formaldehyde) known as formalin. When formalin is used as the source of the aldehyde, impurities present generally include water, methanol, formic acid, methylal, methyl formate and carbon dioxide. The first three of these impurities interfere with polymerisation reactions and need to be removed as much as possible. In commercial polymerisation the low polymers trioxane and paraformaldehyde are convenient sources of formaldehyde since they can be obtained in a greater state of purity. 

Also, the CL aqueous solution may be hydrogenated at 60°C in the presence of 20% sodium hydroxide and 50% palladium absorbed on carbon to provide caprolactam of very high purity after distillation. Treatment with an ion exchange resin before or after the oxidation or hydrogenation process also improves the quality of the CL obtained after distillation. CL has also been purified by treatment with alkali and formaldehyde followed by fractional distillation to remove aromatic amines and other products. 

Paraformaldehyde, (CH20)n where n is between 8 and 100, is a convenient polymer of formaldehyde. The polymer is easily formed by removing water from a 50% formalin solution under reduced pressure. As the formaldehyde concentration increases, crystals of paraformaldehyde form spontaneously. It is available at 91-97% purity. It is more stable than neat formaldehyde but just as useful in applications, where it readily decomposes back to the straight stuff. 

Methyl alcohol of very high purity can be obtained by fractional distillation using a column of 1-3 metres effective length and then refluxing with aluminium amalgam. It is then refluxed under a column packed with dehydrated copper sulphate, to remove ammonia. A sensitive test for acetone and formaldehyde is the addition of cone, mercuric cyanide solution, in 6N-sodium hydroxide. A white precipitate indicates ketone if it darkens on standing aldehyde is also present. (J. C. S., 127, 2552.)... 

In the absorber, the formaldehyde is absorbed in water or urea solution. Heat is removed by one or two cooling circuits (8, 9). From the lower circuit (8), product in the form of either AF or UFC is withdrawn. Scrubbed gas from the absorber is split in two streams—recycle gas and tail gas. The tail gas is vented after any organic impurities are catalytically incinerated in the reactor (10). Thus, the tail-gas purity conforms to the environmental standards for any country. 

Summary In this procedure, propionitrile and sulfuric acid are heated together, and then a solution of trioxane (formaldehyde trimer) in propionitrile is slowly added a short time later. Shortly after the addition, a triazine compound is formed. This triazine compound is only an intermediate and need not be isolated. The triazine slurry is then added to ten times it volume of 99% nitric acid. The resulting mixture is then cooled, heated, and then cooled again. The mixture is then drowned into 5 times its volume of water. The RDX then precipitates in high purity. Commercial Industrial note For related, or similar information, see Application No. 522,153, November 8, 1974, by The United States Army, to Joseph A. Meredith, Bluff City, TN. Part or parts of this laboratory process may be protected by international, and/or commercial/industrial processes. Before using this process to legally manufacture the mentioned explosive, with intent to sell, consult any protected commercial or industrial processes related to, similar to, or additional to, the process discussed in this procedure. This process may be used to legally prepare the mentioned explosive for laboratory, educational, or research purposes. 

A laboratory method 2 for the preparation of sodium hyposulphite depends on the interaction of sodium formaldehydesulphoxylate,3 NaCH303S,2H20, and sodium hydrogen sulphite, the product having a purity of 80 to 85 per cent., and the yield being 55 to 60 per cent, of that theoretically possible. The sodium formaldehydesulphoxylate can be obtained2 by the reduction of commercial hydro-sulphite by zdnc-dust and zinc oxide in presence of formaldehyde solution, the crude product being recrystallized from water at 70° C. 

Materials and Instrumentation. Diallylamine and the various starting materials for monomer synthesis were readily available commercial materials of the highest available purity and were used without further treatment. The formaldehyde used was either BDH analytical reagent solution with 37-40% w/v formaldehyde and 11-14% w/v methanol or BDH analytical reagent paraformaldehyde. 

Initial pressure 5000 p.s.i. Residence period 3 hrs. Catalyst volume 15 cc. Cone, of formaldehyde solution 3.24 mol./l. Volume of formaldehyde solution 15 cc. Purity of carbon monoxide 94.0%. 

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