— 19 — 



G. de Plato 1 ) has made a series of experiments with the object of 

 investigating the conversion of hydrocyanic acid during the ripening of 

 the almonds. His results are summarised below: In the case of bitter 

 almonds the percentage of semi-combined hydrocyanic acid (= acid which 

 can be eliminated by steam-distillation), gradually decreases as the fruit 

 ripens, and disappears completely when it has attained maturity; the 

 percentage of hydrocyanic acid in combination rises until the cotyledons 

 are being formed, after which it decreases, (but without disappearing 

 altogether) until the cotyledons have hardened. In the case of sweet 

 almonds the percentage of semi-combined as well as of glucosidic hydro- 

 cyanic acid decreases when the cotyledons begin to develop, and has 

 disappeared completely when they have hardened. As the fruit matures 

 the nitrogen gradually assumes a stable form as albumen-nitrogen, until 

 the fruit is quite mature, by which time 97,24 °/o of the total nitrogen has 

 assumed this form. This process, therefore, is the reverse of that which 

 takes place during germination, when the albuminous bodies undergo 

 conversion into amygdalin, the new organs requiring for their development 

 the presence of bodies rich in energy-producing constituents. In the process 

 of the maturing of the almonds the amygdalin may be regarded as the 

 intermediate product in the formation of albumen. With sweet almonds the 

 process of conversion of matter is more rapid, preventing the accumulation 

 of amygdalin; in fact, the last-named body is used *up with great rapidity. 



According to P. H. Wirth 2 ), the equilibrium benzaldehyde + hydro- 

 cyanic acid ~~^ benzaldehyde cyanohydrin is obtained no matter whether 

 the reaction proceeds from benzaldehyde cyanohydrin itself or from the 

 two component bodies. With a high degree of dilution the dissociation 

 of benzaldehyde cyanohydrin is increased, with greater concentration it 

 falls. When the concentration remains the same the dissociation in- 

 creases as the temperature is raised, in conformity with the fact that 

 benzaldehyde cyanohydrin is an exothermic compound. The presence 

 of small quantities of alkalies and acids greatly affects the equilibrium- 

 reaction, equilibrium being more rapidly attained in the presence of the 

 OH-ion, while in the presence v of the H-ion both reactions are very greatly 

 retarded. 



Under the influence of alkali the condition of equilibrium is deviated 

 in the direction of a greater decomposition of the cyanohydrin, although 

 fairly high concentrations are not yet followed by a complete decom- 

 position of the cyanohydrin. 



On the testing of benzaldehyde for chlorinated products, see p. 119. 



1 ) Annali della R. Stazione chimico-agraria sperimentale 1910, Ser. II. Vol. IV. Rome 1911. 

 From a copy kindly sent to us by the Director, Prof. G. Ampola. 



2 ) Arch, der Pharm. 249 (1911), 382. 



2* 



