— 186 — 



hydrosulphonate, and citronellal (cinnamic aldehyde) dihydrosulphonite 

 of sodium in aqueous solution. Both salts, viz., citronellal and cin- 

 namic aldehyde sulphite of sodium, according to these investiga- 

 tions, behave differently from the combinations previously investigated, 

 inasmuch as no constant condition of equilibrium occurs in their 

 aqueous solutions under dissociation. In the place thereof there 

 occurs, in addition to the decomposition of the complex of the alde- 

 hyde -sulphite -anion into aldehyde- and bisulphite-ion (which at first 

 proceeds normally and depends upon the concentration of the solution) 

 a second reaction. This consists of the addition of the bisulphite-ion 

 to the portion of the complex which has not been decomposed, the 

 corresponding aldehyde-dihydrosulphonic-acid-anion being formed. Com- 

 pared with the second, the first reaction proceeds rapidly, so that in 

 practice equilibrium of the decomposing-complex may be assumed to 

 exist at any time. In the case of citronellal and in agreement with 

 its greater molecular weight, the dissociation is greater than it is in the 

 cinnamic aldehyde complex. The complex of the citronellal hydro - 

 sulphonic salt does not decompose in aqueous solution: it is therefore 

 a thoroughly stable compound. The same may be the case with the 

 cinnamic aldehyde hydrosulphonic compound. As the latter 

 could not be kept in pure analytical form, the phenyl sulpho- 

 prop ionic acid salt was examined in lieu of it for its behaviour in 

 aqueous solution, and was found to be quite stable. On the other 

 hand the decomposition of the complex of the dihydrosulphonic 

 salts of the two aldehydes is normal, although very slight. In this 

 case the molecule of sulphurous acid which has been added to the 

 double -bond has a certain protective action upon the sulphurous 

 acid which has been added to the aldehyde group, by considerably 

 retarding its abstraction. The addition of the sulphurous acid to the 

 double bond of the aldehyde-sulphite-complex therefore renders the 

 complex considerably more stable. 



Citral. Enklaar 1 ) had already observed that citral, when reduced 

 by Sabatier's method, yields a series of cyclic as well as of aliphatic 

 products. But, as stated by Skita 2 ), the reaction proceeds somewhat 

 differently when palladium chloride and hydrogen are employed; 

 in this case citral gives, besides citronellal and citronellol, a dimole- 

 cular aldehyde. The process takes place in the following manner: 

 the reducing agent, in alcoholic solution, is mixed with an aqueous 

 solution of palladium chloride and gum arabic so as to produce a 

 clear solution. Hydrogen is forced into this solution by pressure. 



*) Chem. Weekblad 4 (1907), 322; Report October 1907, I-13- 

 2 ) Berl. Berichte 42 (1909), 1633. 



