Notes on scientific research. 89 



reason the residue of the dry ethereal extract was a second time shaken with ether. 

 We take the following figures from the solubility tables of the author 1 ): — 



100 parts of water dissolve at 



0.2° 0.68 parts of vanillin and 0.09 parts of coumarin 



20° 1.25 „ „ „ „ 0.11 „ „ 



60° 5.05 „ „ „ „ 0.70 „ „ 



100 parts of 50 percent, glycerin dissolve at 



0.2° 2.06 parts of vanillin and 0.287 parts of coumarin 

 20° 4.5 „ „ „ „ 0.50 „ „ 

 60° 20.0 „ „ „ „ 2.20 „ „ 



As regards adulterations of coumarin, heliotropin and vanillin, cf. page 73 of 

 this Report. 



As regards the determination of chlorine in benzaldehyde, cf. page 53 of this Reports 



As regards the testing of Peru balsam, cf. page 65 of this Report. 



As regards the examination of civet, cf. page 60 of this Report. 



Physical Notes. 



On a previous occasion 2 ) we had proposed the introduction of a standard pressure 

 for the distillation at reduced pressures, also for the purpose of realising connection ^ 

 with the absolute system of measures. Of the pressures then discussed: — 



10 kilobars == 10000 dynes/sq. cm. == 7.5 mm. of mercury, and 

 20 „ =20000 „ „ =15.0 „ „ 



C. von Rechenberg 3 ) selected the pressure of 15 mm. as normal pressure and he re- 

 calculates his well-known tables of boiling points on this basis. The lower pressure 

 of 7.5 mm. is not to be recommended for experimental reasons 4 ). 



In this calculation use has only been made of the more exact determinations of 

 the literature, as well as of a large number of supplementary figures which had been 

 determined in our laboratory. 



For those boiling points which had not been measured exactly at 15 mm. a correc- 

 tion is required which is based upon a formula of Crafts-Young: — 



C = x(15 — p) (273 + t) 



modified for this purpose, where C indicates the correction required for the boiling 

 temperature observed at a pressure p, t is the approximately-estimated boiling point 

 at 15 mm., and x is a coefficient which depends upon the nature of the material and 

 which can be deduced from its vapour-pressure curve. According to the nature of 

 the material definite groups may be distinguished in which the quantity x has an 

 average value, applicable in order to correct other substances, of so-far unknown vapour- 

 pressure curve, to pressures of 15 mm. These average values are: — 



: ) Cf. Gildemcistcr and Hoffmann, The Volatile Oils, 2 nd ed., vol. I, p. 522. — 2 ) Report 1919, 95. — 

 g Jmtrn. f. prakt. Chem. X. F. 101 (1920), 112. — 4 ) Cf. C. von Rechenberg and E. Brauer, Zeitschr. f. physfk, 

 Chem. 95 (1920), 184. 



