— 122 — 



This method is not adapted for the determination of hydrocyanic 

 acid in the presence of benzaldehyde cyanohydrin. 



On estimating the peroxide-content of turpentine oil see p. 93. 



Physical Notes. 



Chr. J. Hansen has published a further contribution to the polemics 

 between himself and von Rechenberg, under the title of "A Final Reply" 

 [Zeitschr. f. physik. Chem. 76 (1911), 753]. The publication contains no 

 new facts. 



Auwers and Eisenlohr 1 ) have continued their spectro-chemical investi- 

 gations to which we referred in our October Report of last year 2 ). They 

 have examined bodies with one pair of conjugated double linkings as well 

 as others with multiple connected conjugations. In order to make 

 distinction easy between the different varieties of the multiple conjugation, 

 they have given to a continuous chain of conjugated double linkings, such, 

 for example, as — C=C— C=C — C=C — , the name of "accumulated 

 conjugation" while systems such as — C=C — C— O are called "crossed 



C = 

 conjugations." The whole of the material has been calculated with the 

 aid of the new atomic refractions drawn up by Eisenlohr 3 ), and the values 

 given in the first paper have also been calculated anew. The term 

 "exaltation of the specific (molecular) refraction and dispersion" has been 

 replaced by the term "specific (molecular) exaltation" (EE). This value, 

 EE S has been calculated for a large number of combinations, both from 

 personal observations and from data ascertained by others. Although 

 apparent contradictions were occasionally noticed, further investigation 

 almost invariably revealed the fact that there is nowhere an absence of 

 rules, notwithstanding the somewhat complicated nature of the optical 

 characteristics of bodies with accumulated and crossed double bonds. 



We are unfortunately precluded from want of space to enter into the 

 details of this valuable experimental material and are compelled to refer 

 for such particulars to the original paper. 



Ciamician and Silber 4 ) have continued their researches 5 ) into the 

 chemical action of light, upon which we have already commented several 

 times. They purified the trimeride of benzaldehyde 6 ) which they had 



x ) Journ. f. prakt. Chem. II. 84 (1911), 1. 



2 ) Comp. Report October 1910, 164. 



3 ) Zeitschr. f. phys. Chem. 75 (1910), 585. Comp. Report April 1911, 155. 

 *) Berl. Berichte 44 (1911), 1559. 



5 ) Report October 1907, 123; October 1909, 159; October 1910, 167. 



,; ) Comp. Report October 1909, 161. 



