M. Soret on the Density of Ozone. 27 



to enter, to emerge, or to diffuse. By means of springs, partly 

 of brass and partly of platinum, the plates were kept pressed 

 against the ends, but not so as to prevent the possibility of 

 sliding them. The edges were lubricated with sulphuric acid, 

 which prevented any escape of gas, provided the pressure did 

 not exceed certain limits which were never attained in the 

 experiments. 



When one of the vessels had been filled with oxygen, and the 

 other with oxygen mixed with a small quantity of chlorine or 

 ozonized oxygen, the first vessel was placed on the second. They 

 were separated by the two glass plates in contact, between which 

 a drop of sulphuric acid had been placed. Communication was 

 then established between the two vessels by sliding the plates 

 until the holes coincided. Diffusion then commenced; the 

 aperture through which it was effected was 5 millims. in dia- 

 meter ; and it was continued for forty-five minutes, at the expira- 

 tion of which time communication was intercepted between the 

 two vessels. 



The proportion of chlorine or of oxygen contained in each 

 vessel at the end of the experiment was determined by passing 

 the gas through iodide of potassium. The disk which closed 

 each tube at its upper extremity consisted of a thick piece of 

 glass with a conical hole, into which fitted the carefully ground 

 conical end of a delivery-tube. When the vessels after diffu- 

 sion had been closed, each was placed over a vessel of sul- 

 phuric acid, into which the lower end dipped to the depth of from 

 2 to 3 centims. The delivery-tube having been fitted to the 

 upper disk, the latter was slid in such a manner that one of the 

 ends of the delivery-tube was under solution of iodide of potas- 

 sium, while the other end was over the interior of the vessel. By 

 means of a glass rod the lower disk was slid away under sulphuric 

 acid so as to open the glass vessel below, and a current of air was 

 admitted so as to drive the gas through the solution of iodide. 

 The quantity of iodine liberated was determined in the ordinary 

 manner. The sum of the quantities of chlorine or of ozone found 

 in the two vessels gave the quantity of gas in the lower vessel 

 at the commencement of the experiment ; the quantity found in 

 the upper vessel represented that which was introduced by diffu- 

 sion. The following results were obtained with mixtures of 

 chlorine and oxygen. 



