— 49 — 
In lemon oil Sad tier determined by this method a citral-content 
of 5,2$^/q, whilst Kremers and Brandel only found on the 
average. But in this connection it should be noted that in both cases 
the determinations were made with only one lemon oil each. 
The method is said to be applicable not only for fatty but also 
for aromatic aldehydes. When putting it to the test, we, however, 
encountered various difficulties, — in the first place with regard to the 
final reaction, the clearness of which leaves something to be desired. 
In neutralising with semi-normal acid the soda liquor split off", the 
original red colouration caused by rosolic acid very gradually changes 
into a pink of increasing brightness, and it is difficult to decide which 
shade has to be considered as decisive for the completion of the reaction. 
But the titration must not be continued up to the stage when the 
solution has become colourless, as in such case results are obtained 
which are too high by several per cent. 
We have also observed that the titration must not in any case be 
carried on at an elevated temperature, as, in consequence of the strong 
dissociation of the sodium sulphite which then takes place, the solution 
always acquires a very vivid red colour, which has nothing to do with 
the actual reaction. For this reason the solution heated on the water- 
bath was each time cooled by us previous to the neutralisation of 
the sodium hydroxide split off. Even after the reaction has long been 
completed, the liquid, for the reason stated, again acquires a vivid red 
colour when it is heated. 
In spite of the negative results obtained up to the present, we do 
not as yet wish to pronounce a definite opinion on Sadtler's method 
of citral- determination; on the contrary, we will make this dependent 
upon further detailed tests. We will return to this matter in our next 
Report. 
The Revue des Cultures coloniales^) contains a short study respecting 
the working up of lemons for the essential oil, juice, citric acid, citrate 
and peel, as it is carried on in Sicily and Calabria. In view of the 
great importance of this industry for the above-named districts, the 
cultivation of lemons is warmly recommended for the French Possessions 
in Indo-China, and calculations are presented which are intended to 
demonstrate how this might become a flourishing industry for Cochin 
China. If the value of i kilo lemon oil is taken as lo francs, a hectare 
(about 2Y2 acres) covered with 300 trees of which each yields 75 kilos 
fruit per year, would produce 2250 kilos fruit, representing a value of 
2025 francs. We would point out in this connection, that the author 
must have been badly informed with regard to the low level of the 
^) Revue des Cultures coloniales 14 (1904), 54. 
4 
