M. Carre on new Apparatus for the Production of Cold. 29 



Here, as in the case of chlorine, it is seen that the quantity- 

 diffused is proportional to the mass of ozone contained in the 

 lower vessel at the commencement of the experiment. But the 

 diffusion of ozone is more rapid than that of chlorine, and it must 

 therefore be concluded that the density of ozone is less than that 

 of chlorine. 



For each cubic centimetre of chlorine originally contained in 

 the lower vessel, 0*227 cubic centim. penetrate into the upper 

 one in forty-five minutes, whereas for each cubic centimetre of 

 ozone 0*271 cubic centim. pass. The ratio of these numbers, 



0*227 



n 9 =0*8382, is very nearly as the inverse ratio of the square 



root of the densities, assuming that the density of ozone is one 



and a half that of oxygen. That is to say, 1>658 =0*8243. 



The ratio is nearer unity than the theoretical one, as ought to be 

 the case. Soret concludes from these experiments, and from 

 analogous ones made with carbonic acid, that the density of ozone 

 prepared by electrolysis is once and a half that of oxygen. 



Carre has given to the French Academy* a description of 

 some new apparatus for producing cold; they are based on 

 Leslie's well-known experiment, and are on such a scale and so 

 certain in their effects as to render them practically useful. 



The first problem to solve was the construction of a simple 

 and inexpensive air-pump which, while easy to construct and 

 work, should produce an exhaustion up to a millimetre without 

 being altered by acid vapours. Such a one was exhibited to the 

 Academy ; it had cost 60 francs, and had been at work without 

 repair for eighteen months ; and it produced ice with acid diluted 

 to 52 degrees. 



The second problem was to combine a mode of contact of 

 aqueous vapour with acid which, without appreciably diminish- 

 ing the gaseous flow, would enable the acid to be diluted so as 

 to obtain the maximum effect. Two principal methods led to 

 this result : the first consists in making a thin stream of acid 

 pass through a tube through which circulates aqueous vapour; 

 the second consisted in terminating the delivery-tube of this 

 vapour by a moveable horizontal jet which skims the surface of 

 the bath of acid, and which ascends in proportion as the acid in- 

 creases in volume by absorbing moisture. 



* Comptes Renchs, May 6, 1867. 



