374« Mr. Williamson on Ozone. 



just described was dried and passed through a small glass tube 

 heated to redness by a spirit-lamp; on coming out of which 

 it had completely lost all odour. At the end of this tube a 

 chloride of calcium tube was then fixed, which had been accur- 

 rately weighed. 



After the oxygen was conducted for a short time through 

 the heated tube, the chloride of calcium tube was found to 

 have increased perceptibly in weight. 



Water through which oxygen charged with ozone was al- 

 lowed to pass assumed the odour of it. When this solution of 

 ozone was added to a solution of iodide of potassium and 

 starch, a pale blue colour was produced; ferro-cyanide of 

 potassium containing ozone gave a blue precipitate with a 

 proto-salt of iron. Lime water formed with the solution of 

 ozone a heavy and apparently crystalline precipitate. Baryta 

 water behaved in a similar manner. The liquid after the pre- 

 cipitation gave no reaction with iodide of potassium and starch ; 

 but on an acid being added, a blue colour immediately ap- 

 peared. The odour did not reappear. 



Oxygen charged with ozone was next passed through a tube 

 surrounded by *a frigoric mixture consisting of chloride of cal- 

 cium and snow; but nothing perceptible was deposited. 



The following experiments were made for the purpose of 

 ascertaining whether, as has been assumed, the substance 

 causing the ozone odour is also produced by the action of 

 phosphorus on atmospheric air. 



Through a glass tube filled with pieces of phosphorus a 

 current of moist atmospheric air was driven by means of a 

 gasometer ; it assumed the peculiar odour so well known to 

 accompany phosphorus. Water, through which this air was 

 then allowed to pass for a considerable time, remained inodo- 

 rous, gave not the slightest reaction with iodide of potassium 

 and starch, left ferro-cyanide of potassium unchanged, and 

 gave all the reactions of a dilute solution of phosphoric acid. 



On repeating this experiment it was performed in a some- 

 what different manner. The air which had passed over phos- 

 phorus was allowed to pass directly into the iodide and 

 starch, and a deep blue reaction soon ensued in that part of 

 the liquid on which the bubbles in passing through first acted ; 

 and was increased, in a greater proportion to the air passing 

 through, when a rapid current of air was driven over the 

 phosphorus instead of a slow one. On again, as in the 

 former instance, passing the air through water and then treat- 

 ing the latter with iodide of potassium and starch, no reaction 

 was obtained. We have here an evident difference between 

 the reactions of the substance contained in the electrolytic 



