— 178 — 



The physical constants of J 3 -m-menthenol-8 and of J 3 ' 8(9) -m-menthadiene 

 agree tolerably well with those of zl 3 -p-menthenol-8 and zl 3 ' 8(9) -p-men- 

 thadiene respectively 1 ). 



When comparing the constants of J 3 ' 8(9) -m- and zl 3 ' 8(9) -p-menthadiene 

 with those of limonene it is noteworthy that the two former hydrocarbons 

 have a higher b. p., a greater density, and a higher refraction than the 

 latter. This is due to the influence of the conjugated double bond. 



On the reaction of iodine with terpineol, see p. 191. 



On the reduction of «- and /^-terpineol and of sylveterpineol, see p. 164. 



On the action of semicarbazide upon terpineol nitrosochloride, see 

 p. 166. 



Aldehydes. 



An article by F. Graziani 2 ) on the influence of the halogens upon 

 phototropy in hydrazones contains a description of a series of hydrazones 

 of various aldehydes of importance in our special branch of industry, to 

 which we will here refer briefly. Benzaldehyde-p-bromo phenylhydrazone 

 forms yellow needles, m. p. 129° (from alcohol) which gradually assume 

 a pink tint, even in the dark. When freshly prepared it shows phototropy, 

 exposed to sunlight it turns pink within 2 or 3 minutes, but the colour 

 disappears again when the body is heated 70 to 75°. Anisic aldehyde-p- 

 bromo phenylhydrazone consists of white leaflets, m. p. 150° (from alcohol) 

 which show no phototropy. Cinnamic aldehyde-p-bromo phenylhydrazone 

 occurs in yellowish-green phototropic needles, m. p. 143° (from alcohol) 

 which turn a greyish-green in from 3 to 4 minutes when exposed to 

 sunlight and become decolorised again at 125 to 130°. Cuminol-p-bromo 

 phenylhydrazone crystallises in yellowish phototropic needles (from alcohol) 

 m. p. 135°, turning red within one minute when exposed to sunlight. 

 When warmed to from 65 to 70° the colour disappears. Piperonal-p-bromo 

 phenylhydrazone crystallises from alcohol, glacial acetic acid, or benzene 

 in white leaflets which melt at 155° and which show no phototropy. 

 Vanillin-p-bromo phenylhydrazone, a body consisting of yellowish leaflets, 

 m. p. 146°, gives no indications of phototropy. Salicylic aldehyde-p-bromo 

 phenylhydrazone forms yellowish, faintly phototropic needles, m. p. 171 

 to 172° which acquire a slight tinge within 3 to 4 minutes after exposure 

 to sunlight. . 



The tendency to form phototropic hydrazones is much less developed 

 in p-bromo phenylhydrazine than in p-toluyl hydrazine. 



*) Comp. Report October 1910, 191. 



2 ) Atti R. Accad. dei Lincei, Roma V. 19 (1910), II. 190. Quoted from Chem. Zentralbl. 

 1910, II. 1212. 



