— 122 — 



is not to be preferred to the two above-mentioned methods, as owing 

 to the bad keeping qualities of the required solutions, it is much 

 too complicated, and takes too much time before the result of the 

 examination is known. For the special purpose of the citral-determination 

 in lemon oil, the method is not reliable enough, to judge the quality 

 of the oil directly from the citral-content; the differences found by us 

 are so large, that judging from the citral-determination alone, greatly 

 adulterated oils might still be passed as satisfactory. 

 The result of our examinations may follow here: 



In a mixture containing 4O°/ citral, we found 39,35% 



>j j> » v 20 /q „ ,, „ I o,93 /o 



» » » ?j 5 /o » " » 4>47 /o 



and 4,86%. 



In a lemon oil whose citral-content had been determined by R other 

 as 5,5%, we found 6°/ and 5,22% respectively. 



Now if we assume that the citral-content of lemon oil fluctuates 

 between 3 and 5% and the results obtained by Ro trier's method 

 are 0,5% too low, an oil with 2,5% citral (according to R other) 

 should, under such circumstances, be allowed to pass, although it 

 might possibly have been produced by mixing a lemon oil containing 

 5°/ citral with say 6o°/ terpenes. But such a coarse adulteration 

 could without question be detected solely by the methods of examination 

 hitherto in use. 



For the detection or identification of certain bodies, such for 

 example as oxygen, carbonic oxide, hydrogen cyanide, etc. the blood- 

 spectrum has now been used for a long time, by observing the changes 

 in the spectra called forth by these bodies. P. Bruylants 1 ) now has 

 recently made use of the spectroscopic behaviour of blood for the 

 detection and the quantitative determination of aldehydes, and 

 also for distinguishing them from ketones. 



During the study of the action of various reducing agents on 

 oxyhsemoglobin he had an opportunity of observing a reliable spectral 

 reaction of haemoglobin which is set up by aldehydes but not by 

 ketones. 



If to an approximately 4 per cent, solution of defibrinated blood 

 is added yellow ammonium sulphide and a small quantity of aldehyde, 

 a reaction is rapidly accomplished, which is recognised by the peculiar 

 spectrum and the brown coloration of the blood solution. The two 

 absorption lines (a and /?) of oxyhemoglobin (a tho the right of the 

 line D, maximum of the absorption at X 580; /J near the line E, 

 maximum of the absorption at X 540) first of all diminish in intensity; 



1 ) Bull, de l'Acad. roy. de Belgique (Classe des sciences) No. 3, 1907, 217. 

 Annales de Pharmacie 13 (1907), 321. 



