1094 



In order to prove tluit this conhiined C5,Cl2 clilorine was passed 

 vvitliont opening the apparatus; after this had been able to act for 

 some time at — 50°, the tube was brought to tiie ordinary' temperature; 

 CjCln was left behind, which by its odour and sublimation phenomena 

 was identified with the pure substance from the collection. 



If the gas diluted with iiydrogen was allowed to pass through a 

 layer of water into the air, the same phenomena were noticed as 

 with liquid hydrogen phosphide ; each bubble coming into contact 

 with the air forms a nebulous ring. 



In a second experiment we started with three grams of barium 

 trichloroacrylate; in the decomposition a more considerable secondary 

 reaction took place so that, finally, tlie quantity of C^Clj collected 

 was estimated not to exceed half a gram. 



When, however, the apparatus was removed, this quantity exploded 

 with the fatal result that one of us (Carriiire) suffered a very serious 

 injury to the eye. 



Hence, dichloroacetylene is decidedly much more dangerous than 

 dibromoacetylene ^), because it decomposes with explosion by slight 

 mechanical influences even without exposure to the air. 



We have discontinued our researches in this direction and think 

 we must warn our colleagues against this exceedingly treacherous 

 compound. 



The decomposition of barium trichloroacrylate is in agreement 

 with that of the /?-halogenates in general where the elimination of 

 the metallic haloid salt must be considered as the first phase of 

 the reaction, 



It is remarkable that also in the case of chlorine atoms combined 

 with unsaturated carbon, this tendency to form salts is so great that 

 an energetic compound such as dichloroacetylene can be formed in 

 considerable quantities. 



Let us summarize the properties of dichloroacetylene : 

 It is a colourless gas with a disgustingly sweet odour. ^) In a very 

 diluted condition it exhibits chemo-luminosity ; in a somewhat more 

 concentrated form in admixture with H2 and a little CO2 it takes 

 fire in the air. 



1) Lemoult C. R. 136, 55 (1903); 137, 1333 (1903). 



-) It is probable that Dr. Prins has already observed this substance in the 

 decomposition of one of the higher condensation products of CH CP with C- Gl'^ H; 

 there was then also formed from a hydrogen-free carbon chloride compound under 

 the influence of an alkali, a gas exploding in contact with the air having a 

 disgustingly sweet odour. (Dissertation H. J. Prins Delft 1912 p. 160---162). 



