Hydrogen cyanide physical properties

The physical properties of cyanoacetic acid [372-09-8] and two of its ester derivatives are Hsted ia Table 11 (82). The parent acid is a strong organic acid with a dissociation constant at 25°C of 3.36 x 10. It is prepared by the reaction of chloroacetic acid with sodium cyanide. It is hygroscopic and highly soluble ia alcohols and diethyl ether but iasoluble ia both aromatic and aUphatic hydrocarbons. It undergoes typical nitrile and acid reactions but the presence of the nitrile and the carboxyUc acid on the same carbon cause the hydrogens on C-2 to be readily replaced. The resulting malonic acid derivative decarboxylates to a substituted acrylonitrile ... 

The physical properties of hydrogen cyanide are Hsted in Table 1. 

Cyanohydrins are usually colorless to straw yellow Hquids with an objectionable odor akin to that of hydrogen cyanide. The lower molecular-weight cyanohydrins can be distilled under reduced pressure provided the cyanohydrin is kept at a slightly acidic pH. Table 2 Hsts physical properties of some common cyanohydrins. 

Hydrogen cyanide (HCN) is a colorless, highly poisonous gas or liquid (below 26.7 °C) having an odor of bitter almonds (Hartung 1994 Pesce 1994). It is a weak acid. Exposures may occur in industrial situations as well as from cigarette smoke and combustion products and from naturally occurring cyanide compounds in foods. There is a potential for exposure when any acid is mixed with a cyanide salt. Intravenously administered sodium nitroprusside (Na2[Fe(CN)5N0]-2H20) has been used clinically to lower blood pressure (Schulz et al. 1982). Chemical and physical properties are listed in Table 5-2. 

By-products of this reaction are acetonitrile, CH3-C=N, and hydrogen cyanide. This is now a major source of these two materials. Interestingly, the C2 by-product acetonitrile has a bp of 81.6 °C, whereas acrylonitrile with three carbons has a lower bp of 77.3 °C, quite an unusual reversal of this physical property s dependence on molecular weight. The TWA of acrylonitrile is 2 ppm and it is on the list of Reasonably Anticipated to Be Human Carcinogens. ... 

Physical Properties. o -Aminomtriles are stable at modest temperatures (<70°C in the absence of water in the presence of water, they can degrade to their original constituents, i.e., ketone (aldehyde), ammonia and hydrogen cyanide if insufficient ammonia is present. The aminoiiilriles based on ketones are clear colorless liquids, but sometimes appear yellow to brown depending on the synthetic procedure and the amount of decomposition. They are soluble in polar organic solvents and in aromatic solvents. 

Hydrogen cyanide, a colorless liquid, is similar, in many of its physical properties, to water.320 This similarity also explains the limitless solubility of HCN in water and its strong tendency towards absorption (dissolution) in water. The equilibrium concentration321 of hydrogen cyanide in water is investigated in more detail in chapter... 

Hydrogen cyanide, HCN, is also known as hydrocyanic acid, prussic acid and formonitrile. Although HCN is a colorless liquid, iron cyanide is blue (Prussian blue) and its presence as a slight contaminant usually gives HCN a bluish tint that led to the German name Blausaure - blue acid. Selected physical properties of hydrogen cyanide are shown in Table 19.1. 

Table 19.1. Physical Properties of Hydrogen Cyanide - continued...

Hydrogen cyanide is a colorless, poisonous liquid with a boiling point of 25.1° C (ATSDR 1997). Thus, at room temperature, hydrogen cyanide exists primarily as a gas. It has a faint odor of bitter almonds (ATSDR 1997), although not everyone is able to smell it (Hall and Rumack 1986). The chemical and physical properties of hydrogen cyanide are summarized in Table 6-1. 

TABLE 6-1 Summary of Physical and Chemical Properties for Hydrogen Cyanide ... 

Toxic chemicals tliat could potentially cause a major problem if accidentally released into tlie atmosphere include clilorine, hydrogen fluoride, hydrogen chloride, ammonia, chloropicrin, gasoline lead additives, vinyl cliloridc. and benzene. Hiis chapter addresses the process application of some chemicals from the foregoing list, as well as some others that are considered to be highly toxic hydrogen cyanide, sulfuric acid, and etliylene. Process considerations, physical and chemical properties, healtli effects, and metliods of manufacture of tliese chemicals are discussed in conjunction with potential causes of release. 

---