M 



Mi; U.IU. (TTHBKRTSON AND MAUDE CUTHBERTSON ON THE 



M , VKTS gM wm pnfMd from ammonium nitrate Mad itaim-,1 10 per cent, 



of impurity. 



The gas we used was obtained from two sources: (l) The commercial gas, 

 obtained in cylinders, condensed and fractionated at the temperature of liquid air, and 

 (2) gas prepared by the action of ammonium nitrite on hydroxylamine hydrosulphate. 

 It was bubbled through strong potash and dried with sulphuric acid and phosphorus 

 pentoxide. 



/,' t'l-.i.-tir,: Index. Three sets of experiments on different samples gave 



In reducing these experiments the coefficient of thermal expansion used was 

 00371. 



The purity of the gas was tested by absorption in an excess of water boiled in 

 vacua. The bubble of gas left unabsorbed was not so great as 1/2000 of the whole ; 

 and even this was probably due to the error of the test experiment, which is not very 

 easy. But as traces of air were probably present we think 5100 a more trustworthy 

 value than the exact experimental mean, and probably correct to 1/500 at least. 



Dispersion. From five experiments the following values were obtained for the 

 dispersion : 



TABLE XIV. 



