Pyrogenic decomposition

Hydrogen cyanide apparatus, 7, 50 Manipulation of gases, 4, 24 Mechanical stirrer, 1, 4, 12, 3, 29 Mercury seal, 1, 4 Pyrogenic decomposition, 4, 40 Rapid evaporation, 4, 54 Steam distillation, 1, 50, 2, 80... 

In addition to the above method, based upon the work of Schmidlin and Bergman 1 as modified by Hurd and Cochran,2 ketene has been prepared by the pyrogenic decomposition of acetic anhydride,3 of ethyl acetate, and of triacetin.4 In the last instance, acrolein and acetic acid are formed simultaneously. 

Benzyl Chloride, benzal chloride and benzotrichloridej when subjected like chloroform to pyrogenic decomposition, behave quite like the latter compound a dissociation into hydrochloric acid, or chlorine and phenylmethylene, or chlorphenyl-methylene, seems to occur first (Lob1). 

If a mixture of benzotrichloride and water is subjected to pyrogenic decomposition, the yield of tolane diehlorides, tri- and tetrachlorides is very small, although these substances do not entirely disappear. Benzaldehyde and benzoic acid become the chief products. The benzaldehyde is apparently the reaction product of ehlorphenylmethylene with water, and the benzoic acid the oxidation product of the benzaldehyde by the intermediately occurring chlorine. Benzalchloride, in the presence of water, gives benzaldehyde no benzoic acid is formed. 

Method of Pyrogenic Decomposition. One of the most widely used methods for the detection of chloropicrin in air consists in decomposing it by heat and then testing for chlorine in the products. 

The Flame Test. Another method of detection, also based on the pyrogenic decomposition of chloropicrin, consists in passing the gas mixture to be examined into a gas jet, the flame of which maintains a copper spiral at red heat. ... 

Processes of this sort have been classified under the general name of pyrogenic decomposition and may be differentiated into two types (1) those which take place under the action of heat alone, and (2) those which take place under the action of heat in the presence of a catalyst. Tn the former case the product of the reaction frequently consists of a very complex mixture, the character of which is determined by the temperature, pressure and time of contact.8 In the latter case, the course of the reaction may in certain instances be so controlled as to favor the formation of a single product. The procedure may be varied by passing the vapor of the substance through a tube or chamber the walls of which arc themselves inactive but into which an appropriate catalyst has been introduced. This latter modification of the reaction has been made the. subject of careful investigation by Ipatiew, who was indeed the first to call attention to the definite quantitative differences in the amounts of (a) acetaldehyde and (b) ethylene which resulted from the pyrogenic decomposition of ethanol under the action of specific catalysts. 

With the exception of formic acid, the lower fatty acids are quite stable np to relatively high temperatures. Cahours and Berthelot early notedos the thermal stability of these acids, and the latter reported that acetic acid did not decompose until above a dull red heat. More recently Senderens showed that acetic, propionic, /i-butyric, isobutyric, and isovaleric acids were perfectly stable at temperatures as high as 460° C.os At higher temperatures these acids undergo pyrogenic decomposition to yield simple and stable substances. In the case of acetic acid, Nef 01 reported the presence of methane, carbon dioxide, carbon monoxide, ethylene, hydrogen, and acetone in the products from decomposition. 

Carboxylic acids that are difficult to decarboxylate comprise in particular the aliphatic acids and simple aromatic carboxylic acids. They can be decarboxylated only by pyrogenic decomposition of their salts in admixture with an alkali hydroxide or lime. In such mixtures an additional charge produced on the carboxyl group makes it possible, by induction, to remove the group R as an anion ... 

Staudinger, H., R. Endle, and J. Herold Uber die pyro-gene Zersetzung von Butadien-Kohlenwasserstoffen [Pyrogenic decomposition of butadiene hydrocarbons] Ber. Dtsch. Chem. Ges. 46 (1913) 2466-2477. 

Paracelsus (c, 1490—1541), physician and philosopher on the nature of man and the origin of sickness, seems to have been the first to discover the element of lire ii>4he residue of the pyrogenic decomposition of urine. More than a century later (1669), the alchemist Brandt discovered or rediscovered the waxy material that miraculously glowed without heat in the dark and that caught fire on the slightest provocation. Brandt had distilled (i.e. decomposed by heat) urine in the absence of air in the course of an experiment that was to lead to the conversion of silver into gold. 

Pyrogenic decomposition at low temperatures of organic salts such as tartrates. This process yields self-ignitible metal powders of small particle sizes,... 

Beside the tartrate, other organic salts—notably the oxalate and the formate—yield the more easily produced pyrophoric metals, i.e. lead, nickel, and cobalt, if the pyrogenic decomposition is performed at low temperature. These organic salts or the oxides of nickel, cobalt, and iron, under hydrogen at about 300X, also furnish the self-flammable metals, but in the case of iron, a pyrophoric ferrous oxide (FeO) may first appear by reduction with hydrogen as well as by reduction under carbon monoxide. 

Undoubtedly, one can produce other gases by pyrochemical reaction or by combining a heat source with a pyrogenic decomposition reaction. These include the halogens and pseudo halogens, such as cyanogen. The latter is formed from heavy-metal cyanides ... 

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