266 



MR. V. H. VELEY ON THE CONDITIONS OF THE 



latter, for from the one 25 observations of 10 c.c. each were taken, out of a possible 

 165 ; from the other only 16 or 17, out of the same number. 



Decomposition of Nitric Acid into Nitric Oxide and Water by means of Ferrous Sulphate. 

 6FeSO 4 + 5H 2 SO 4 + 2KNO 3 = 3Fe 2 (SO 4 ) 3 -4- 2KHSO 4 + 4H 2 + 2NO. 



A convenient method of preparing pure nitric oxide gas consists in heating ferrous 

 sulphate and potassium nitrate with dilute sulphuric acid. A mixture was made up 

 as follows : 6 grams of potassium nitrate and 36 grams ferrous sulphate were 

 dissolved in 100 c.c. water; the solution filtered to rid it of small quantities of a basic 

 iron sulphate, which invariably separated out ; to this solution was added gradually a 

 previously made and cooled mixture of 40 c.c. sulphuric acid and 20 c.c. water. The 

 twin U-tube method was used. 



Effect of Pumice. 



Temperature 34'8-35-2. 



The introduction of the pumice produced a most violent effervescence ; some quantity 

 of the liquid frothed over. The above results show that, notwithstanding the loss of 

 mass due to this effervescence, the interval of time in which 10 c.c. of gas is given off 

 is suddenly reduced from 11''37 to 2' - 9. 



Effect of Graphite. 



The experiment above was repeated, graphite being introduced instead of pumice ; 

 the phenomena observed were precisely similar. 

 Temperature 39 '4-397. 



