91-C.] 



FORMIC ALDEHYDE 



169 



ALDEHYDES AND KETONES : FATTY GROUP. 



91. Formic Aldehyde ; Formalde- 

 hyde; Metlianal. 



H .CHO 



NATURAL SOURCES. 



The aldehyde may possibly exist in 

 plant cells containing chlorophyll (Rein- 

 ke, Ber. 14, 2148; Mori, Jahresber. 

 1882, 1143), but this observation re- 

 quires confirmation. The distilled 

 extract of witch - hazel, Ilamamelis 

 virginica, N. America, is said to contain 

 formic aldehyde (Gunn, Ch. Drug. 

 59, 796). Polacci claims to have ob- 

 tained distinct evidence of the presence 

 of the aldehyde in the distillate from 

 the leaves of plants which have been 

 exposed to light (Ch. Centr. 1899, 2, 

 88 1, from Boll. Chim. Pharm. 38, 601 ; 

 also Ch. Centr. 1900, 1, 822 ; 1901, 2, 



SYNTHETICAL PROCESSES. 



[A.] From carbon dioxide and hydro- 

 gen by the silent electric discharge 

 (Brodie, Proc. Roy. Soc. 22, 172); from 

 carbon dioxide and water under the 

 influence of sunlight in presence of 

 uranium acetate (Bach, Comp. Rend. 

 116, 1 145; I 3^9)- From carbon mon- 

 oxide and hydrogen by the silent electric 

 discharge (Losanitsch and Jovitschitsch, 

 Ber. 30, 136; De Hemptinne, Bull. 

 Acad. Roy. Belg. 34, 269 ; Solvay and 

 Slosse, Ibid. 35, 547), or by passing over 

 hot spongy platinum (Jahn, Ber. 22, 

 989). 



From carbonic acid (carbon dioxide 

 in water) by reduction with hydrogen- 

 palladium or by electrolytic reduction 

 (Bach, Comp. Rend. 126, 479), or by the 

 action of violet light in presence of 

 uranium acetate (Ibid. Arch. Soc. Phys. 

 Nat. Geneve [4] 5, 401 ; Ch. Centr. 

 1898, 2, 42). 



From acetylene [l; A, &c.], the silver, 

 mercury, or cuprous compounds of 

 which, as well as the sulphuric acid so- 

 lution, all yield iodoform on treatment 

 with iodine and alkali (Le Comte, Journ. 



Pharm. 16, 297). From iodoform, as 

 below under D. 



[B.] Methane [l] and oxygen give 

 formic aldehyde by the action of the 

 silent electric discharge (Maquenne, 

 Bull. Soc. [2] 37, 298). 



Or from methane and air by passing 

 over heated catalytic surfaces of copper, 

 asbestos, &c. (Glock, Germ. Pat. 109014 

 of 1898; Ch. Centr. 1900, 2, 304), or 

 by slow combustion at low temperatures 

 with oxygen (Bone and Wheeler, Proc. 

 Ch. Soc. 19, 191 ; Trans. 83, 1074). 



[C.] From methyl alcohol [13] by in- 

 complete combustion in air (Hofmann, 

 Proc. Roy. Soc. 16, 156; Ber. 2, 152; 11, 

 1685; Ann. 145, 357; Volhard, Ann. 

 176, 128 ; Kablukoff, Journ. Russ. Soc. 



14, 194; Tollens, Ber. 15, 1629; 16, 

 917; 19, 2133; Loew, Journ. pr. Ch. 

 [2] 33, 321 ; Ber. 20, 144; Klar and 

 Schulze, Germ. Pat. 106495 of 1898 ; 

 Ch. Centr. 1900, 1, 1082). From 

 methyl alcohol (trace only) by oxidation 

 with air in a solution containing col- 

 loidal platinum (Glaessner, Ch. Centr. 

 1902, 2, 731). 



Also from methyl alcohol by electro- 

 lytic oxidation in sulphuric acid solution 

 (Elbs and Brunner, Zeit. Elektroch. 6, 

 604) or by pyrogenic decomposition 

 (Ipatieff, Ber. 34, 598 ; 35, 1055). 



Or from methyl alcohol through 

 methyl ether (Dumas and Peligot, Ann. 



15, 12; Kane, Ann. 19, 166 ; Ebelmen, 

 Ann. 57, 328 ; Erlenmeyer and Kriech- 

 baumer, Ber. 7, 699 ; Tellier, Jahresber. 

 1877, 1157). The latter gives formic 

 aldehyde by pyrogenic decomposition 

 (Tistschenko, Journ. Russ. Soc. 31, 

 784 ; Ch. Centr. 1900, 1, 586). 



Or from methyl alcohol through 

 methylal by oxidation with sulphuric 

 acid and manganese dioxide (Kane, 

 Ann. 19, 175; Malaguti, Ann. 32, 55), 

 or by electrolysis of the alcohol in di- 

 lute sulphuric acid (Renard, Ann. Chim. 

 [5] 17, 291). Methylal gives formic 

 aldehyde when heated with sulphuric 

 acid, the aldehyde rapidly polymerising 

 (Wohl, Ber. 19, 1841). 



