144 Report of Schimmel $ Co. 1922. 



Polymerisation of the most unstable acrolein to insoluble disacryl may be prevented, 

 as was found by Ch. Moureu, Ch. Dufraisse, P.Robin, and }. Pougnet 1 ), by adding a 

 small amount of phenols or bodies containing such, such as pyrogallol (in proportion 

 1 : 1000), pyrocatechol or hydroquinone (1 : 500), gallic acid (1 : 250), or ethereal tannin 

 solution (1 : 100). Extracts of tanning agents act in the same manner. These phenols 

 are likewise capable of arresting the once started polymerisation of acrolein. The 

 aldehyde, when treated wifh these agents, remains stable for years, provided that it 

 is kept in the dark and at a temperature not exceeding 30°. 



Gitral. — E. Knoevenagel and G. Oelbermann 2 ) have continued the work of the 

 first-named author 3 ) on testing the constitution of compounds of the citral series by 

 optical methods. The values observed by the authors of the specific normal exaltation 

 of citral were in good accord with the figures observed formerly by v. Auwers and 

 Eisenlohr, as well as with those found by the last-named investigator for the system 

 — C(R) : CH • CHO (E -Retr. 1.25; E ^djs P . 45 per cent.). Whereas a preparation of citral after 

 keeping for 48 hours at a temperature of — 190° had suffered a slight change (the 

 refractive index rising from 1.48786 to 1.48821), another preparation remained unchanged 

 after the same treatment. After three months' standing in the same sealed bottles,, the 

 preparation, on optical examination, showed a strong increase in density and a decrease 

 in the molecular refraction... Possibly, it was the case of polymerisation, or oxidation, 

 or of both. 



With pseudoionone, the authors obtained values equally in good accord with those 

 recorded by Eisenlohr for the system — C(R) : CH-CH : CHC(R): O (E^Retr. somewhat 

 above 2.7; E-Dis P . above 110 percent). The optical constants remained unchanged 

 after cooling the preparation down to — 190° for 300 hours. 



From pseudoionone, y-ionone acetate was prepared according to Knoevenagel, by 

 means of acetic anhydride with addition of sublimed ferric chloride. B.p. 145 to 146° 

 (15 mm.). Basing on the values read off for the exaltations (E^Rgfr. -{-0-29 and -{- 0.42 ; 

 E^-Disp. + 7 and -f- 8 per cent.) the authors suggest formula (1) for the acetate, although 

 they admit that various %omerides may be present. This assumption is rendered 

 probable by the wide b. p. range of the freshly-prepared acetate, the main part of 

 which boiled from 118 to 150° at 11 mm. No alteration of the optical values was 

 noticed after cooling down to — 190° during 300 hours. 



For iso-y-ionone, obtained from the preceding acetate by boiling with alcoholic 

 caustic potash (b. p. 128 to 129° at 13 mm.) the author suggest formula (II) in view 

 of the exaltations found (E^Refr. +2.22 and +0.39; E^ D is P . +10 and + 14 percent). 

 Cooling down to — 190°, for 300 hours, did not affect the body; however, after ten 

 hours' standing in an open vessel the molecular refraction, by oxidation, rose from 

 1.49805 to 1.50311, and after 17 hours to 1.50350. The semicarbazone, m. p. 189°, was 

 identical with a semicarbazone obtained in the same manner from ^-ionone acetate. 



By abstracting water from y-ionone with zmc chloride, the authors obtained two 

 fractions of a hydrocarbon (not quite pure, b.p. 90 to 122° [12 mm.] and 135 to 145° 

 [21 mm.]), concerning the constitution of which nothing certain could be stated from 

 the optical data or the chemical reactions (preparation of an oxidation-product). 



The optical dispersion observed with «-citrylidene acetoacetic ester was some- 

 what too low, since that body is easily rearranged into the /?-isomeride and therefore 



l ) Process for stabilising acrolein. Germ. Pat. Appi. M/64903, April 7, 1921. — 2 ) Journ. f. prakt. Vh 

 W. F. 102 (1921), 305. — s ) Cf. He-purt 1911), 147. 



