bal =~ s i. 4 * 
60 REPORT OF SCHIMMEL & Co. OCTOBER 1914/ APRIL 1915. a 
out that, in order to get comparable figures, the temperatures must always be read 
under the same conditions. Whereas analysts are used to read as melting point the 
temperature at which a solid substance is completely melted, the German Pharma- 
copoeia considers as melting point the degree at which the solid body flows together — 
in the melting tube, before being entirely melted. It is therefore necessary to distinguish — 
between the melting point of the German Pharmacopoeia V and clear melting. Much 
stress is laid on the shrinking, which, as is known, enables one to make reliable 
conclusions as to the purity of the substance. The purer the preparation, the closer 
together are the temperatures of shrinking and clear melting, whereas the differences 
-are greatly enhanced already by traces of organic solvents, such as benzene, light 
petroleum, toluene, Sc. 
The sulphuric acid test is only of conditional value for estimating vanillin, but - 
combined with other tests it may afford a clue as to the purity of the preparation. 
Lehmann carried out his investigation as follows: in a cylinder with glass stopper, 
holding about 30 cc. and which has carefully been rinsed with pure concentrated 
sulphuric acid, 1 g. of vanillin is vigorously shaken with 10 cc. of pure concentrated 
sulphuric acid. Pure products dissolve in the acid with orange-yellow colour, whereas . 
inferior ones show a dark yellow to brown colour, according to the kind and quantity 
of impurities. Lehmann obtained the following results through his investigations :— 
Franz Fritzsche & Co.’s guayacol-vanillin 
vanillin from clove oil of different origin 
shrinking «. 5. me in ee T7-AG: 7904 
m. p. aS per German Paarniacopoeia i chae lee jacc a 80°37 Sie 
clear nielting: . ..)ca.oes nn See ‘ 81.4, 81,52 
solidification point... «0. .« % 96 *48L9 tos68Z22 81.5; Sia 
sulphuric acid test. . . » s. . «= .Orfange-yellow: orange-yellow to brown 
He further added, in varying proportions, to pure vanillin the different substances 
which occur as adulterants and observed the changes in the temperatures of shrinking 
and melting, taking into consideration the above observations. In the original treatise, 
the results are perspicuously arranged in the form of tables and are further explained 
by graphic figures. In addition, it is described how the presence of some well-known 
adulterants, such as coumarin, heliotropin, benzoic acid, salicylic acid and antifebrin, 
can be proved. | 
A publication by C. F. Boehringer & Soehne’), who manufacture vanillin from guayacol, 
is directed against Lehmann’s assertion in his treatise referred to that vanillin from 
clove oil is superior to that from guayacol. At the request of this firm, the Mannheim 
municipal laboratory examined both kinds of vanillin (Franz Fritzsche & Co.’s vanillin 
from clove oil and C. F. Boehringer & Soehne’s vanillin from guayacol) and found that 
there was no difference at all in the behaviour when melting, whereas the sulphuric 
acid test resulted in favour of vanillin from guayacol:— 
eugenol-vanillin guayacol-vanillin 
(Franz Fritzsche & Co.) (Boehringer &§ Soehne) 
shrinking... 80,7 ° 80,7° 
m.p. aS per German ‘Pharmacopoeia Wis Si;22 81322 
Slearimelting 3S... .0abhias @ eee 81,5° 
solidification point . . . 78,9 and 78,85° 78,9 and 78,95° 
id. id. according to Lehmann 80,0 and 80,1° 79,95 and 79,9° .. 
sulphuric acid-test . . . ..... «4. dark orangeyellow vivid yellow 
1) Chem. Ztg. 39 (1915), 31. 
q 
