— 167 — 



From a subsequent paper by Auwers in conjunction with Roth 1 ), it 

 appears that, in addition to the optical properties, the determination of 

 the thermic value of a body may also be used with success in deter- 

 mining its constitution. But the laws which rule the applicability of this 

 test can be accurately studied only if proper care is taken in the gauging 

 of the calorimetric system, a factor to which the earlier investigators 

 have not always paid sufficient attention. Although not provided with 

 the costly apparatus which was used by Fischer and Wrede 2 ) in their 

 standard examinations, Roth 3 ) has nevertheless succeeded in so accurately 

 gauging his calorimeter as to make it possible to compare his results with 

 those of Fischer and Wrede, the more so because most of the compounds 

 subjected to examination were terpene hydrocarbons, which, as is well-known, 

 cannot be prepared in an absolutely pure state. Theoretical values, such 

 as are available for refraction and dispersion, are non-existent in the 

 case of the determination of the thermic value; Auwers and Roth 4 ) 

 therefore, in order the better to compare the thermic with the optical 

 behaviour of the terpenes examined by them, have assumed as the normal 

 value (1464) the average caloric value of the three hydrocarbons with two 

 non-conjugated double bonds, to wit, limonene, dipentene, and sylvestrene. 

 These values lie close together. 



We must refer to the original paper for the experimental details of these 

 interesting experiments, of which the optical part is to be described in 

 detail later on in another publication. The calorimetric investigations cover 

 limonene, dipentene, sylvestrene, «-phellandrene, carvenene, «-terpinene, 

 d-a-pinene, l-«-pinene, camphene (liquid), and sabinene, the materials having 

 been supplied by us to the authors. 



Ciamician and Silber 5 ), in one of their former communications on the 

 chemical action of light, announced that they were engaged in experiments 

 on the action of light upon fenchone and camphor. This investigation 

 has now been completed, and the authors have obtained the results 

 summarised below 6 ): — From camphor which in aqueous-alcoholic solution 

 had been exposed to light, acetaldehyde had separated out, and also an 

 aldehyde which yielded a hydroxamic acid melting at 118°. This was 

 most probably camphenolenic aldehyde, the formation of which would be 

 accounted for by disruption of the camphor-ring: — 



J ) Liebigs Annalen 373 (1910), 239. 



2 ) Sitzungsbericht der Berliner Akademie 1904, 687. 



3 ) Liebigs Annalen 373 (1910), 249. 



4 ) Ibidem 267. 



T >) Berl. Berichte41 (1908), 1928; Report November 1908, 158; Rendiconti della R. Accademia 

 dei Lincei 39 (1910), Series Va, p. 532. 

 «) Berl. Berichte 36 (1910), 1340. 



