206 



Lord Rayieigh. On the Densities of Carbonic 



hydrogen in carbonic oxide is also difficult to reconcile with the well- 

 known experiments of Professor Dixon, who found that prolonged 

 treatment with phosphoric anhydride was required in order to render 

 the mixture of carbonic oxide and oxygen inexplosive. In the 

 presence of relatively large quantities of free hydrogen (or hydro- 

 carbons) why should traces of water vapour be so important ? 



In an experiment by Dr. Scott,* 4 litres of carbon monoxide gave 

 only 1*3 milligrams to the drying tube after oxidation. 



I have myself made several trials of the same sort with gas pre- 

 pared from formate of soda exactly as for weighing. The results 

 were not so concordant as I had hoped, t but the amount of water 

 collected was even less than that given by Dr. Scott. Indeed, I do 

 not regard as proved the presence of hydrogen at all in the gas that 

 I have employed. % 



Carbonic Anhydride. 



This gas was prepared from hydrochloric acid and marble, and 

 after passing a bubbler charged with a solution of carbonate of soda, 

 was dried by phosphoric anhydride. Previous to use, the acid was 

 caused to boil for some time by the passage of hydrochloric acid 

 vapour from a flask containing another charge of the acid. In a 

 second set of experiments the marble was replaced by a solution of 

 carbonate of soda. There is no appreciable difference between the 

 results obtained in the two ways ; and the mean, corrected for the 

 errors of weights and for the shrinkage of the globe when exhausted, 

 is 3"6349, corresponding to 2 - 6276 for oxygen. The temperature at 

 which the globe was charged was 0° 0., and the actual pressure that 

 of the manometric gauge at about 20°, reduction being made to 15° 

 by the use of Boyle's law. From the former paper it appears that the 

 actual height of the mercury column at 15° is 762*511 mm. 



Nitrous Oxide. 



In preliminary experiments the gas was prepared in the labora- 

 tory, at as low a temperature as possible, from nitrate of ammonia, 

 or was drawn from the iron bottles in which it is commercially sup- 

 plied. The purification was by passage over potash and phosphoric 

 anhydride. Unless special precautions are taken the gas so obtained 

 is ten or more milligrams too light, presumably from admixture with 



* ' Chem. Soc. Trans.,' 1897, p. 564 



f One obstacle was the difficulty of re-oxidising the copper reduced by carbonic 

 oxide. I have never encountered this difficulty after reduction by hydrogen. 



X In Mr. Richards' work the gas in an imperfectly dried condition was treated 

 with hot platinum black. Is it possible that the hydrogen was introduced at this 

 stage ? 



