Mat 11, 1906.] 



SCIENCE. 



753 



stances which were not suitable for investi- 

 gation. 



Some time ago Professor C. Harries, in the 

 course of an investigation of caoutchouc, 

 studied its behavior towards ozone. The re- 

 sults were not very conclusive, but they led 

 him to take up the wider question of the in- 

 teraction of ozone with organic compounds in 

 general. He has published various brief 

 papers on the subject, from time to time, dur- 

 ing the interval and quite recently he has 

 collected his results into a longer article' 

 which is of considerable interest. 



The first requisite was the provision of an 

 adequate supply of ozone, of relatively high 

 concentration, and for this purpose a special 

 form of generator was devised by Siemens and 

 Halske. The experiments were conducted as 

 follows: The substance under investigation is 

 dissolved in chloroform, or low boiling ligroin, 

 the solution cooled in a freezing mixture and 

 ozonized oxygen passed into it. To minimize 

 the danger of explosion a current of carbon 

 dioxide is directed through the apparatus, 

 which must be thoroughly well dried; mois- 

 ture in the materials must also be rigorously 

 excluded. 



The experimental results lead to the conclu- 

 sion that all organic compounds containing 

 an ethylene linkage (double bond) add one 

 molecule of ozone, giving rise to a new class 

 of substances termed ozonides: 



>C:C<-)-03-»>C — C<. 



I I 

 — 



\// 







It will be observed that Harries formulates • 

 the oxygen as tetravalent; he is, however, not 

 wholly consistent on this point in his paper 

 and, in any case, the results can be just as 

 accurately expressed by the bivalent formula. 

 The ozonides are viscid oils, or colorless, vitre- 

 ous syrups, more or less explosive and possess- 

 ing an unpleasant, suffocating smell ; some of 

 them can be distilled under reduced pressure. 

 They liberate iodine from potassium iodide 

 and bleach indigo solution. 



^Ann. ahem. (Liebig), 343, 311. 



The most interesting reaction of the ozonides 

 is with water, with which they yield hydrogen 

 peroxide and aldehydes or ketones : 



> C — < -F H,0 -»■ > CO + > CO + HjO-. 



V 



Thus, from allylamine hydrochloride, the cor- 

 responding salt of aminoacetaldehyde is ob- 

 tained : 



HCI .NHjCHjCHiCHj 



-» HCI . NH^CHjCH — CH, 



V 



-> HCI . NH.CHoCHO + HCHO. 



This method of work has already proved its 

 value in permitting the comparatively easy 

 preparation, in fairly large quantity, of many 

 substances which were hitherto unknown, or 

 could only be obtained with the greatest diffi- 

 culty. Another, equally valuable feature of 

 the research, is the application of the reaction 

 to the determination of the constitution of 

 compounds. Of many of the examples given in 

 the original paper, one must suffice for quota- 

 tion. According to Kekule's formula benzene 

 has three double bonds, whereas, according to 

 the ' centric ' formula it has none. If the 

 former be correct benzene should add 3 mole- 

 cules of ozone and the resulting product, when 

 treated with water, should yield glyoxal. This 

 is exactly what really happens, the triozonide. 



O 



o-y 



CH 

 /\ 

 / \. 



HC 



O— HQ 



X \ \/ 

 ()=0 CH 



V 



HOJ^ 



which is first formed, yields, with water, 

 30CHCH0. This constitutes one of the 

 strongest, purely chemical supports for the 

 Kekule formula which has been discovered 

 for many years. 



