Be = anil Pieacder the. suctiod gave very nearly He iepretical value, as was 
lished by ourselves. de Jong is of opinion that in presence of geraniol a part of 
c tronellal also suffers esterification i in the same moperion with the Beenie! present. 
= On the estimation of aldehydes and pe Many iaethiods sie been worked out 
Bice: purpose and have been discussed for the major part: in our Reports. L. Lauten- 
and for ketones and aliphatic aldehydes with acid hydrazides. 
| s The author has found that the aromatic aldehydes react quantitatively orien stake 
with the ‘molecular amount of aqueous hydrazine solution. The estimation is carried 
unt of hydrazine sulphate solution in excess, the strength of which is previously 
rtained by titration against iodine. The mixture is then let to stand for a couple 
ours, when the following reaction takes place: — — 
w2'Res CHO + NH, H:SO, = R- CH: Ng: CH- R-+2H.0 + H2SOx. 
Oe is freed from the precipitate formed by filtration and the filtrate filled up 
nc ot consumed in the reaction is estimated iodometrically by adding a certain amount 
th | acidifying the solution after the evolution of nitrogen has passed off, _and titrating 
the excess of iodine with sodium hyposulphite. The aldehyde present is calculated from 
the -hyposulphite solution used for titrating back. 
» For transforming one molecule of hydrazine into the aldazine, fae molecules of 
al ¢ Mchyde are required, as is evident from the Fuabon above. Furthermore, 4 atoms 
7 dine correspond to 1 molecule of hydrazine: a 
Seek NH,- NH: +2l = No+4HI, 
o that 2 ‘molecules aldehyde are equivalent to 4 atoms iodine. 
* 
only incompletely, and often not at all, with hydrazine. In such cases the use 
f acid hydrazides, ¢c. g. benzhydrazide, proved to be successful. These hydrazides may 
hyde s and ketones in accord with the hone Renee fa Mepis 
ket ones and aldehydes the reaction remains incomplete but is quantitative with the 
Se1 T ries. The titration is carried out in the same manner as described above with hydrazine 
sul phate, the interaction, however, between the acid hydrazide and the carbonyl deri- 
V azine. The aqueous solution of the hydrazide (the amount of which having been 
4 Sad estimated iodometrically) is therefore shaken for some time with a weighed 
nount of the substance under examination, using here again an excess of the hydrazide. 
he e interaction is complete only after 12 to 24 hours, although a precipitate is generally 
'™ ed eee after mixing both substances. After that time the precipitate is 
— i a. , «x 
_ 4) Arch. der Pharm. 256 (1918), TAS: age irr 
ba -< ae } 
t . 
+; &. 
ager ‘') now describes anew method for titrating aromatic aldehydes with bagtee i 
as follows: - — About 1 g. of the aldehyde under examination is mixed with a certain 
to a certain volume. In a corresponding part of this solution the amount of the hydrazine | 
f iodine solution in excess, then making the liquid alkaline by. addition of caustic soda, 
- amount of hydrazine sulphate solution taken in reaction, Wie iodine Solution ae 
s _ This method is not applicable with ketones and aliphatic aldehydes, since they : 
e Sp be titrated iodometrically and react quantitatively with a large number of alde- 
_ The apeeatici-prodijets fined are aahubie in water. ‘With the lower Alionade | 
ligher aliphatic aldehydes as well as with numerous. carbonyl compounds of the terpene ~ 
es mentioned proceeds in the most cases far slower than. the condensation of. 
