SS TET ae ee 
20 REPORT OF SCHIMMEL & Co. OCTOBER 1914/APRIL 1915. be 
This table may be completed ad lib., every additional 1 p.c. of hydrocarbon ‘cor- ; 2, 
responding with 0,66 p.c. less citral percentage. Thus, when examining a concentrated — 
lemon oil, a glance at above table shews whether the hydrocarbon percentage found - 
in the oil is in accordance with the citral percentage. If the oil contains more citral 
. than is permissible according to this table, it is a proof of adulteration with lemon- 
grass citral. Based on the highest permissible citral percentage (table), corresponding 
to the ascertained amount of hydrocarbon, the minimum added quantity of foreign 
citral is found by calculating how much lemon oil citral should be contained at most 
in the oil under examination. This figure is deducted from the percentage of citral 
as established by the sulphite method. The difference indicates the minimum of 
adulteration. 
From one of the examples adduced by Bocker, the manner of calculation is ex- 
plained more clearly. If in a given oil 15 p.c. of hydrocarbons and 61 p.c. citral have 
been found, a reference to above table shows that these values are not in agreement, 
for in an oil containing 15 p.c. of hydrocarbons the citral percentage should not 
exceed 56 p.c. The oil must, therefore, have been mixed with foreign citral. As a 
normal oil, showing 56 p.c. citral, should contain 100 —56 = 44 p.c. of non-citral 
parts, and as the oil under examination contains only 100 — 61 = 39 p.c. of non-citral 
parts, the citral normally corresponding with the latter is shewn by the following ratio: 
44:56 :: 39:x; x = 49,03. This figure indicates the highest possible percentage of real 
lemon oil citral in an oil containig 39 p.c. of non-citral bodies. 61 p.c. having been 
found, there must have been an adulteration with at least 61 — 49,63 = 11,37 p.c. of 
added foreign citral. 
Whether this manner of valuation can safely be relied upon in a general way for 
concentrated oils prepared by different manufacturing methods would have to be 
ascertained first by special experiments. It must not be lost sight of that besides 
hydrocarbons other bodies may have been eliminated from the original oil, according 
to the process that may have been made use of. In our. opinion it does not neces- 
sarily follow that a high citral percentage is the result of adulteration. 
For the determination of citral in lemon oils and lemon extracts, L. D. Little’) has 
elaborated a new colorimetric method. As a reagent he uses amidol (diamidophenol 
dihydrochloride), which is useful inasmuch as it does not react with acetaldehyde. 
It is not necessary, therefore, to specially purify the ethyl alcohol used for the solution, 
though it is advisable to distil it over caustic potash before use. The process is 
similar to Chace’s method’), but is simpler, as there is no necessity of heating any 
of the solutions; the work may be carried out at ordinary room temperature. All that 
is required is an amido solution (0,2 g. amidol in 100 cc. of 65 p.c. alcohol) and a 
solution of citral in 50 p.c. alcohol containing 0,001 g. of citral per cc. Of this latter, 
which serves for comparison purposes, exactly 2 cc. are placed in a colorimetric tube, 
20 cc. of 65 p.c. alcohol and 15 cc. of amidol solution are added and the mixture 
brought to a total of 50 cc. by adding 65 p.c. alcohol. 
In similar manner a small quantity is mixed with a solution of the lemon oil or 
extract to be tested. The mixture is well shaken and allowed to settle for about 5 or 
10 minutes, when the maximum coloration has been reached. The colour shades are 
then compared and the percentage of citral computed therefrom. In case of need 
1) Americ. Perfumer 9 (1914), 74. — *) Comp. Report April 1907, 116. 
ed en. 
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the experiment is repeated after 15 to 20 minutes. In the case of extracts a 50 p.c. 
